drivers/gpu/drm/i915/dvo_ns2501.c - maze/linux - Git at Google

 /*
  *
  * Copyright (c) 2012 Gilles Dartiguelongue, Thomas Richter
  *
  * All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the
  * "Software"), to deal in the Software without restriction, including
  * without limitation the rights to use, copy, modify, merge, publish,
  * distribute, sub license, and/or sell copies of the Software, and to
  * permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
  *
  * The above copyright notice and this permission notice (including the
  * next paragraph) shall be included in all copies or substantial portions
  * of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  *
  */

 #include "dvo.h"
 #include "i915_reg.h"
 #include "i915_drv.h"

 #define NS2501_VID 0x1305
 #define NS2501_DID 0x6726

 #define NS2501_VID_LO 0x00
 #define NS2501_VID_HI 0x01
 #define NS2501_DID_LO 0x02
 #define NS2501_DID_HI 0x03
 #define NS2501_REV 0x04
 #define NS2501_RSVD 0x05
 #define NS2501_FREQ_LO 0x06
 #define NS2501_FREQ_HI 0x07

 #define NS2501_REG8 0x08
 #define NS2501_8_VEN (1<<5)
 #define NS2501_8_HEN (1<<4)
 #define NS2501_8_DSEL (1<<3)
 #define NS2501_8_BPAS (1<<2)
 #define NS2501_8_RSVD (1<<1)
 #define NS2501_8_PD (1<<0)

 #define NS2501_REG9 0x09
 #define NS2501_9_VLOW (1<<7)
 #define NS2501_9_MSEL_MASK (0x7<<4)
 #define NS2501_9_TSEL (1<<3)
 #define NS2501_9_RSEN (1<<2)
 #define NS2501_9_RSVD (1<<1)
 #define NS2501_9_MDI (1<<0)

 #define NS2501_REGC 0x0c

 struct ns2501_priv {
 	//I2CDevRec d;
 	bool quiet;
 	int reg_8_shadow;
 	int reg_8_set;
 	// Shadow registers for i915
 	int dvoc;
 	int pll_a;
 	int srcdim;
 	int fw_blc;
 };

 #define NSPTR(d) ((NS2501Ptr)(d->DriverPrivate.ptr))

 /*
  * For reasons unclear to me, the ns2501 at least on the Fujitsu/Siemens
  * laptops does not react on the i2c bus unless
  * both the PLL is running and the display is configured in its native
  * resolution.
  * This function forces the DVO on, and stores the registers it touches.
  * Afterwards, registers are restored to regular values.
  *
  * This is pretty much a hack, though it works.
  * Without that, ns2501_readb and ns2501_writeb fail
  * when switching the resolution.
  */

 /*
 ** Read a register from the ns2501.
 ** Returns true if successful, false otherwise.
 ** If it returns false, it might be wise to enable the
 ** DVO with the above function.
 */
 static bool ns2501_readb(struct intel_dvo_device *dvo, int addr, uint8_t * ch)
 {
 	struct ns2501_priv *ns = dvo->dev_priv;
 	struct i2c_adapter *adapter = dvo->i2c_bus;
 	u8 out_buf[2];
 	u8 in_buf[2];

 	struct i2c_msg msgs[] = {
 		{
 		 .addr = dvo->slave_addr,
 		 .flags = 0,
 		 .len = 1,
 		 .buf = out_buf,
 		 },
 		{
 		 .addr = dvo->slave_addr,
 		 .flags = I2C_M_RD,
 		 .len = 1,
 		 .buf = in_buf,
 		 }
 	};

 	out_buf[0] = addr;
 	out_buf[1] = 0;

 	if (i2c_transfer(adapter, msgs, 2) == 2) {
 		*ch = in_buf[0];
 		return true;
 	};

 	if (!ns->quiet) {
 		DRM_DEBUG_KMS
 		    ("Unable to read register 0x%02x from %s:0x%02x.\n", addr,
 		     adapter->name, dvo->slave_addr);
 	}

 	return false;
 }

 /*
 ** Write a register to the ns2501.
 ** Returns true if successful, false otherwise.
 ** If it returns false, it might be wise to enable the
 ** DVO with the above function.
 */
 static bool ns2501_writeb(struct intel_dvo_device *dvo, int addr, uint8_t ch)
 {
 	struct ns2501_priv *ns = dvo->dev_priv;
 	struct i2c_adapter *adapter = dvo->i2c_bus;
 	uint8_t out_buf[2];

 	struct i2c_msg msg = {
 		.addr = dvo->slave_addr,
 		.flags = 0,
 		.len = 2,
 		.buf = out_buf,
 	};

 	out_buf[0] = addr;
 	out_buf[1] = ch;

 	if (i2c_transfer(adapter, &msg, 1) == 1) {
 		return true;
 	}

 	if (!ns->quiet) {
 		DRM_DEBUG_KMS("Unable to write register 0x%02x to %s:%d\n",
 			      addr, adapter->name, dvo->slave_addr);
 	}

 	return false;
 }

 /* National Semiconductor 2501 driver for chip on i2c bus
  * scan for the chip on the bus.
  * Hope the VBIOS initialized the PLL correctly so we can
  * talk to it. If not, it will not be seen and not detected.
  * Bummer!
  */
 static bool ns2501_init(struct intel_dvo_device *dvo,
 			struct i2c_adapter *adapter)
 {
 	/* this will detect the NS2501 chip on the specified i2c bus */
 	struct ns2501_priv *ns;
 	unsigned char ch;

 	ns = kzalloc(sizeof(struct ns2501_priv), GFP_KERNEL);
 	if (ns == NULL)
 		return false;

 	dvo->i2c_bus = adapter;
 	dvo->dev_priv = ns;
 	ns->quiet = true;

 	if (!ns2501_readb(dvo, NS2501_VID_LO, &ch))
 		goto out;

 	if (ch != (NS2501_VID & 0xff)) {
 		DRM_DEBUG_KMS("ns2501 not detected got %d: from %s Slave %d.\n",
 			      ch, adapter->name, dvo->slave_addr);
 		goto out;
 	}

 	if (!ns2501_readb(dvo, NS2501_DID_LO, &ch))
 		goto out;

 	if (ch != (NS2501_DID & 0xff)) {
 		DRM_DEBUG_KMS("ns2501 not detected got %d: from %s Slave %d.\n",
 			      ch, adapter->name, dvo->slave_addr);
 		goto out;
 	}
 	ns->quiet = false;
 	ns->reg_8_set = 0;
 	ns->reg_8_shadow =
 	    NS2501_8_PD | NS2501_8_BPAS | NS2501_8_VEN | NS2501_8_HEN;

 	DRM_DEBUG_KMS("init ns2501 dvo controller successfully!\n");
 	return true;

 out:
 	kfree(ns);
 	return false;
 }

 static enum drm_connector_status ns2501_detect(struct intel_dvo_device *dvo)
 {
 	/*
 	 * This is a Laptop display, it doesn't have hotplugging.
 	 * Even if not, the detection bit of the 2501 is unreliable as
 	 * it only works for some display types.
 	 * It is even more unreliable as the PLL must be active for
 	 * allowing reading from the chiop.
 	 */
 	return connector_status_connected;
 }

 static enum drm_mode_status ns2501_mode_valid(struct intel_dvo_device *dvo,
 					      struct drm_display_mode *mode)
 {
 	DRM_DEBUG_KMS
 	    ("%s: is mode valid (hdisplay=%d,htotal=%d,vdisplay=%d,vtotal=%d)\n",
 	     __FUNCTION__, mode->hdisplay, mode->htotal, mode->vdisplay,
 	     mode->vtotal);

 	/*
 	 * Currently, these are all the modes I have data from.
 	 * More might exist. Unclear how to find the native resolution
 	 * of the panel in here so we could always accept it
 	 * by disabling the scaler.
 	 */
 	if ((mode->hdisplay == 800 && mode->vdisplay == 600) ||
 	    (mode->hdisplay == 640 && mode->vdisplay == 480) ||
 	    (mode->hdisplay == 1024 && mode->vdisplay == 768)) {
 		return MODE_OK;
 	} else {
 		return MODE_ONE_SIZE;	/* Is this a reasonable error? */
 	}
 }

 static void ns2501_mode_set(struct intel_dvo_device *dvo,
 			    struct drm_display_mode *mode,
 			    struct drm_display_mode *adjusted_mode)
 {
 	bool ok;
 	int retries = 10;
 	struct ns2501_priv *ns = (struct ns2501_priv *)(dvo->dev_priv);

 	DRM_DEBUG_KMS
 	    ("%s: set mode (hdisplay=%d,htotal=%d,vdisplay=%d,vtotal=%d).\n",
 	     __FUNCTION__, mode->hdisplay, mode->htotal, mode->vdisplay,
 	     mode->vtotal);

 	/*
 	 * Where do I find the native resolution for which scaling is not required???
 	 *
 	 * First trigger the DVO on as otherwise the chip does not appear on the i2c
 	 * bus.
 	 */
 	do {
 		ok = true;

 		if (mode->hdisplay == 800 && mode->vdisplay == 600) {
 			/* mode 277 */
 			ns->reg_8_shadow &= ~NS2501_8_BPAS;
 			DRM_DEBUG_KMS("%s: switching to 800x600\n",
 				      __FUNCTION__);

 			/*
 			 * No, I do not know where this data comes from.
 			 * It is just what the video bios left in the DVO, so
 			 * I'm just copying it here over.
 			 * This also means that I cannot support any other modes
 			 * except the ones supported by the bios.
 			 */
 			ok &= ns2501_writeb(dvo, 0x11, 0xc8);	// 0xc7 also works.
 			ok &= ns2501_writeb(dvo, 0x1b, 0x19);
 			ok &= ns2501_writeb(dvo, 0x1c, 0x62);	// VBIOS left 0x64 here, but 0x62 works nicer
 			ok &= ns2501_writeb(dvo, 0x1d, 0x02);

 			ok &= ns2501_writeb(dvo, 0x34, 0x03);
 			ok &= ns2501_writeb(dvo, 0x35, 0xff);

 			ok &= ns2501_writeb(dvo, 0x80, 0x27);
 			ok &= ns2501_writeb(dvo, 0x81, 0x03);
 			ok &= ns2501_writeb(dvo, 0x82, 0x41);
 			ok &= ns2501_writeb(dvo, 0x83, 0x05);

 			ok &= ns2501_writeb(dvo, 0x8d, 0x02);
 			ok &= ns2501_writeb(dvo, 0x8e, 0x04);
 			ok &= ns2501_writeb(dvo, 0x8f, 0x00);

 			ok &= ns2501_writeb(dvo, 0x90, 0xfe);	/* vertical. VBIOS left 0xff here, but 0xfe works better */
 			ok &= ns2501_writeb(dvo, 0x91, 0x07);
 			ok &= ns2501_writeb(dvo, 0x94, 0x00);
 			ok &= ns2501_writeb(dvo, 0x95, 0x00);

 			ok &= ns2501_writeb(dvo, 0x96, 0x00);

 			ok &= ns2501_writeb(dvo, 0x99, 0x00);
 			ok &= ns2501_writeb(dvo, 0x9a, 0x88);

 			ok &= ns2501_writeb(dvo, 0x9c, 0x23);	/* Looks like first and last line of the image. */
 			ok &= ns2501_writeb(dvo, 0x9d, 0x00);
 			ok &= ns2501_writeb(dvo, 0x9e, 0x25);
 			ok &= ns2501_writeb(dvo, 0x9f, 0x03);

 			ok &= ns2501_writeb(dvo, 0xa4, 0x80);

 			ok &= ns2501_writeb(dvo, 0xb6, 0x00);

 			ok &= ns2501_writeb(dvo, 0xb9, 0xc8);	/* horizontal? */
 			ok &= ns2501_writeb(dvo, 0xba, 0x00);	/* horizontal? */

 			ok &= ns2501_writeb(dvo, 0xc0, 0x05);	/* horizontal? */
 			ok &= ns2501_writeb(dvo, 0xc1, 0xd7);

 			ok &= ns2501_writeb(dvo, 0xc2, 0x00);
 			ok &= ns2501_writeb(dvo, 0xc3, 0xf8);

 			ok &= ns2501_writeb(dvo, 0xc4, 0x03);
 			ok &= ns2501_writeb(dvo, 0xc5, 0x1a);

 			ok &= ns2501_writeb(dvo, 0xc6, 0x00);
 			ok &= ns2501_writeb(dvo, 0xc7, 0x73);
 			ok &= ns2501_writeb(dvo, 0xc8, 0x02);

 		} else if (mode->hdisplay == 640 && mode->vdisplay == 480) {
 			/* mode 274 */
 			DRM_DEBUG_KMS("%s: switching to 640x480\n",
 				      __FUNCTION__);
 			/*
 			 * No, I do not know where this data comes from.
 			 * It is just what the video bios left in the DVO, so
 			 * I'm just copying it here over.
 			 * This also means that I cannot support any other modes
 			 * except the ones supported by the bios.
 			 */
 			ns->reg_8_shadow &= ~NS2501_8_BPAS;

 			ok &= ns2501_writeb(dvo, 0x11, 0xa0);
 			ok &= ns2501_writeb(dvo, 0x1b, 0x11);
 			ok &= ns2501_writeb(dvo, 0x1c, 0x54);
 			ok &= ns2501_writeb(dvo, 0x1d, 0x03);

 			ok &= ns2501_writeb(dvo, 0x34, 0x03);
 			ok &= ns2501_writeb(dvo, 0x35, 0xff);

 			ok &= ns2501_writeb(dvo, 0x80, 0xff);
 			ok &= ns2501_writeb(dvo, 0x81, 0x07);
 			ok &= ns2501_writeb(dvo, 0x82, 0x3d);
 			ok &= ns2501_writeb(dvo, 0x83, 0x05);

 			ok &= ns2501_writeb(dvo, 0x8d, 0x02);
 			ok &= ns2501_writeb(dvo, 0x8e, 0x10);
 			ok &= ns2501_writeb(dvo, 0x8f, 0x00);

 			ok &= ns2501_writeb(dvo, 0x90, 0xff);	/* vertical */
 			ok &= ns2501_writeb(dvo, 0x91, 0x07);
 			ok &= ns2501_writeb(dvo, 0x94, 0x00);
 			ok &= ns2501_writeb(dvo, 0x95, 0x00);

 			ok &= ns2501_writeb(dvo, 0x96, 0x05);

 			ok &= ns2501_writeb(dvo, 0x99, 0x00);
 			ok &= ns2501_writeb(dvo, 0x9a, 0x88);

 			ok &= ns2501_writeb(dvo, 0x9c, 0x24);
 			ok &= ns2501_writeb(dvo, 0x9d, 0x00);
 			ok &= ns2501_writeb(dvo, 0x9e, 0x25);
 			ok &= ns2501_writeb(dvo, 0x9f, 0x03);

 			ok &= ns2501_writeb(dvo, 0xa4, 0x84);

 			ok &= ns2501_writeb(dvo, 0xb6, 0x09);

 			ok &= ns2501_writeb(dvo, 0xb9, 0xa0);	/* horizontal? */
 			ok &= ns2501_writeb(dvo, 0xba, 0x00);	/* horizontal? */

 			ok &= ns2501_writeb(dvo, 0xc0, 0x05);	/* horizontal? */
 			ok &= ns2501_writeb(dvo, 0xc1, 0x90);

 			ok &= ns2501_writeb(dvo, 0xc2, 0x00);
 			ok &= ns2501_writeb(dvo, 0xc3, 0x0f);

 			ok &= ns2501_writeb(dvo, 0xc4, 0x03);
 			ok &= ns2501_writeb(dvo, 0xc5, 0x16);

 			ok &= ns2501_writeb(dvo, 0xc6, 0x00);
 			ok &= ns2501_writeb(dvo, 0xc7, 0x02);
 			ok &= ns2501_writeb(dvo, 0xc8, 0x02);

 		} else if (mode->hdisplay == 1024 && mode->vdisplay == 768) {
 			/* mode 280 */
 			DRM_DEBUG_KMS("%s: switching to 1024x768\n",
 				      __FUNCTION__);
 			/*
 			 * This might or might not work, actually. I'm silently
 			 * assuming here that the native panel resolution is
 			 * 1024x768. If not, then this leaves the scaler disabled
 			 * generating a picture that is likely not the expected.
 			 *
 			 * Problem is that I do not know where to take the panel
 			 * dimensions from.
 			 *
 			 * Enable the bypass, scaling not required.
 			 *
 			 * The scaler registers are irrelevant here....
 			 *
 			 */
 			ns->reg_8_shadow |= NS2501_8_BPAS;
 			ok &= ns2501_writeb(dvo, 0x37, 0x44);
 		} else {
 			/*
 			 * Data not known. Bummer!
 			 * Hopefully, the code should not go here
 			 * as mode_OK delivered no other modes.
 			 */
 			ns->reg_8_shadow |= NS2501_8_BPAS;
 		}
 		ok &= ns2501_writeb(dvo, NS2501_REG8, ns->reg_8_shadow);
 	} while (!ok && retries--);
 }

 /* set the NS2501 power state */
 static bool ns2501_get_hw_state(struct intel_dvo_device *dvo)
 {
 	unsigned char ch;

 	if (!ns2501_readb(dvo, NS2501_REG8, &ch))
 		return false;

 	if (ch & NS2501_8_PD)
 		return true;
 	else
 		return false;
 }

 /* set the NS2501 power state */
 static void ns2501_dpms(struct intel_dvo_device *dvo, bool enable)
 {
 	bool ok;
 	int retries = 10;
 	struct ns2501_priv *ns = (struct ns2501_priv *)(dvo->dev_priv);
 	unsigned char ch;

 	DRM_DEBUG_KMS("%s: Trying set the dpms of the DVO to %i\n",
 		      __FUNCTION__, enable);

 	ch = ns->reg_8_shadow;

 	if (enable)
 		ch |= NS2501_8_PD;
 	else
 		ch &= ~NS2501_8_PD;

 	if (ns->reg_8_set == 0 || ns->reg_8_shadow != ch) {
 		ns->reg_8_set = 1;
 		ns->reg_8_shadow = ch;

 		do {
 			ok = true;
 			ok &= ns2501_writeb(dvo, NS2501_REG8, ch);
 			ok &=
 			    ns2501_writeb(dvo, 0x34,
 					  enable ? 0x03 : 0x00);
 			ok &=
 			    ns2501_writeb(dvo, 0x35,
 					  enable ? 0xff : 0x00);
 		} while (!ok && retries--);
 	}
 }

 static void ns2501_dump_regs(struct intel_dvo_device *dvo)
 {
 	uint8_t val;

 	ns2501_readb(dvo, NS2501_FREQ_LO, &val);
 	DRM_LOG_KMS("NS2501_FREQ_LO: 0x%02x\n", val);
 	ns2501_readb(dvo, NS2501_FREQ_HI, &val);
 	DRM_LOG_KMS("NS2501_FREQ_HI: 0x%02x\n", val);
 	ns2501_readb(dvo, NS2501_REG8, &val);
 	DRM_LOG_KMS("NS2501_REG8: 0x%02x\n", val);
 	ns2501_readb(dvo, NS2501_REG9, &val);
 	DRM_LOG_KMS("NS2501_REG9: 0x%02x\n", val);
 	ns2501_readb(dvo, NS2501_REGC, &val);
 	DRM_LOG_KMS("NS2501_REGC: 0x%02x\n", val);
 }

 static void ns2501_destroy(struct intel_dvo_device *dvo)
 {
 	struct ns2501_priv *ns = dvo->dev_priv;

 	if (ns) {
 		kfree(ns);
 		dvo->dev_priv = NULL;
 	}
 }

 struct intel_dvo_dev_ops ns2501_ops = {
 	.init = ns2501_init,
 	.detect = ns2501_detect,
 	.mode_valid = ns2501_mode_valid,
 	.mode_set = ns2501_mode_set,
 	.dpms = ns2501_dpms,
 	.get_hw_state = ns2501_get_hw_state,
 	.dump_regs = ns2501_dump_regs,
 	.destroy = ns2501_destroy,
 };
	/*
	*
	* Copyright (c) 2012 Gilles Dartiguelongue, Thomas Richter
	*
	* All Rights Reserved.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the
	* "Software"), to deal in the Software without restriction, including
	* without limitation the rights to use, copy, modify, merge, publish,
	* distribute, sub license, and/or sell copies of the Software, and to
	* permit persons to whom the Software is furnished to do so, subject to
	* the following conditions:
	*
	* The above copyright notice and this permission notice (including the
	* next paragraph) shall be included in all copies or substantial portions
	* of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
	* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	* ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
	* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
	* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*
	*/

	#include "dvo.h"
	#include "i915_reg.h"
	#include "i915_drv.h"

	#define NS2501_VID 0x1305
	#define NS2501_DID 0x6726

	#define NS2501_VID_LO 0x00
	#define NS2501_VID_HI 0x01
	#define NS2501_DID_LO 0x02
	#define NS2501_DID_HI 0x03
	#define NS2501_REV 0x04
	#define NS2501_RSVD 0x05
	#define NS2501_FREQ_LO 0x06
	#define NS2501_FREQ_HI 0x07

	#define NS2501_REG8 0x08
	#define NS2501_8_VEN (1<<5)
	#define NS2501_8_HEN (1<<4)
	#define NS2501_8_DSEL (1<<3)
	#define NS2501_8_BPAS (1<<2)
	#define NS2501_8_RSVD (1<<1)
	#define NS2501_8_PD (1<<0)

	#define NS2501_REG9 0x09
	#define NS2501_9_VLOW (1<<7)
	#define NS2501_9_MSEL_MASK (0x7<<4)
	#define NS2501_9_TSEL (1<<3)
	#define NS2501_9_RSEN (1<<2)
	#define NS2501_9_RSVD (1<<1)
	#define NS2501_9_MDI (1<<0)

	#define NS2501_REGC 0x0c

	struct ns2501_priv {
	//I2CDevRec d;
	bool quiet;
	int reg_8_shadow;
	int reg_8_set;
	// Shadow registers for i915
	int dvoc;
	int pll_a;
	int srcdim;
	int fw_blc;
	};

	#define NSPTR(d) ((NS2501Ptr)(d->DriverPrivate.ptr))

	/*
	* For reasons unclear to me, the ns2501 at least on the Fujitsu/Siemens
	* laptops does not react on the i2c bus unless
	* both the PLL is running and the display is configured in its native
	* resolution.
	* This function forces the DVO on, and stores the registers it touches.
	* Afterwards, registers are restored to regular values.
	*
	* This is pretty much a hack, though it works.
	* Without that, ns2501_readb and ns2501_writeb fail
	* when switching the resolution.
	*/

	/*
	** Read a register from the ns2501.
	** Returns true if successful, false otherwise.
	** If it returns false, it might be wise to enable the
	** DVO with the above function.
	*/
	static bool ns2501_readb(struct intel_dvo_device dvo, int addr, uint8_t ch)
	{
	struct ns2501_priv *ns = dvo->dev_priv;
	struct i2c_adapter *adapter = dvo->i2c_bus;
	u8 out_buf[2];
	u8 in_buf[2];

	struct i2c_msg msgs[] = {
	{
	.addr = dvo->slave_addr,
	.flags = 0,
	.len = 1,
	.buf = out_buf,
	},
	{
	.addr = dvo->slave_addr,
	.flags = I2C_M_RD,
	.len = 1,
	.buf = in_buf,
	}
	};

	out_buf[0] = addr;
	out_buf[1] = 0;

	if (i2c_transfer(adapter, msgs, 2) == 2) {
	*ch = in_buf[0];
	return true;
	};

	if (!ns->quiet) {
	DRM_DEBUG_KMS
	("Unable to read register 0x%02x from %s:0x%02x.\n", addr,
	adapter->name, dvo->slave_addr);
	}

	return false;
	}

	/*
	** Write a register to the ns2501.
	** Returns true if successful, false otherwise.
	** If it returns false, it might be wise to enable the
	** DVO with the above function.
	*/
	static bool ns2501_writeb(struct intel_dvo_device *dvo, int addr, uint8_t ch)
	{
	struct ns2501_priv *ns = dvo->dev_priv;
	struct i2c_adapter *adapter = dvo->i2c_bus;
	uint8_t out_buf[2];

	struct i2c_msg msg = {
	.addr = dvo->slave_addr,
	.flags = 0,
	.len = 2,
	.buf = out_buf,
	};

	out_buf[0] = addr;
	out_buf[1] = ch;

	if (i2c_transfer(adapter, &msg, 1) == 1) {
	return true;
	}

	if (!ns->quiet) {
	DRM_DEBUG_KMS("Unable to write register 0x%02x to %s:%d\n",
	addr, adapter->name, dvo->slave_addr);
	}

	return false;
	}

	/* National Semiconductor 2501 driver for chip on i2c bus
	* scan for the chip on the bus.
	* Hope the VBIOS initialized the PLL correctly so we can
	* talk to it. If not, it will not be seen and not detected.
	* Bummer!
	*/
	static bool ns2501_init(struct intel_dvo_device *dvo,
	struct i2c_adapter *adapter)
	{
	/* this will detect the NS2501 chip on the specified i2c bus */
	struct ns2501_priv *ns;
	unsigned char ch;

	ns = kzalloc(sizeof(struct ns2501_priv), GFP_KERNEL);
	if (ns == NULL)
	return false;

	dvo->i2c_bus = adapter;
	dvo->dev_priv = ns;
	ns->quiet = true;

	if (!ns2501_readb(dvo, NS2501_VID_LO, &ch))
	goto out;

	if (ch != (NS2501_VID & 0xff)) {
	DRM_DEBUG_KMS("ns2501 not detected got %d: from %s Slave %d.\n",
	ch, adapter->name, dvo->slave_addr);
	goto out;
	}

	if (!ns2501_readb(dvo, NS2501_DID_LO, &ch))
	goto out;

	if (ch != (NS2501_DID & 0xff)) {
	DRM_DEBUG_KMS("ns2501 not detected got %d: from %s Slave %d.\n",
	ch, adapter->name, dvo->slave_addr);
	goto out;
	}
	ns->quiet = false;
	ns->reg_8_set = 0;
	ns->reg_8_shadow =
	NS2501_8_PD \| NS2501_8_BPAS \| NS2501_8_VEN \| NS2501_8_HEN;

	DRM_DEBUG_KMS("init ns2501 dvo controller successfully!\n");
	return true;

	out:
	kfree(ns);
	return false;
	}

	static enum drm_connector_status ns2501_detect(struct intel_dvo_device *dvo)
	{
	/*
	* This is a Laptop display, it doesn't have hotplugging.
	* Even if not, the detection bit of the 2501 is unreliable as
	* it only works for some display types.
	* It is even more unreliable as the PLL must be active for
	* allowing reading from the chiop.
	*/
	return connector_status_connected;
	}

	static enum drm_mode_status ns2501_mode_valid(struct intel_dvo_device *dvo,
	struct drm_display_mode *mode)
	{
	DRM_DEBUG_KMS
	("%s: is mode valid (hdisplay=%d,htotal=%d,vdisplay=%d,vtotal=%d)\n",
	__FUNCTION__, mode->hdisplay, mode->htotal, mode->vdisplay,
	mode->vtotal);

	/*
	* Currently, these are all the modes I have data from.
	* More might exist. Unclear how to find the native resolution
	* of the panel in here so we could always accept it
	* by disabling the scaler.
	*/
	if ((mode->hdisplay == 800 && mode->vdisplay == 600) \|\|
	(mode->hdisplay == 640 && mode->vdisplay == 480) \|\|
	(mode->hdisplay == 1024 && mode->vdisplay == 768)) {
	return MODE_OK;
	} else {
	return MODE_ONE_SIZE; /* Is this a reasonable error? */
	}
	}

	static void ns2501_mode_set(struct intel_dvo_device *dvo,
	struct drm_display_mode *mode,
	struct drm_display_mode *adjusted_mode)
	{
	bool ok;
	int retries = 10;
	struct ns2501_priv ns = (struct ns2501_priv )(dvo->dev_priv);

	DRM_DEBUG_KMS
	("%s: set mode (hdisplay=%d,htotal=%d,vdisplay=%d,vtotal=%d).\n",
	__FUNCTION__, mode->hdisplay, mode->htotal, mode->vdisplay,
	mode->vtotal);

	/*
	* Where do I find the native resolution for which scaling is not required???
	*
	* First trigger the DVO on as otherwise the chip does not appear on the i2c
	* bus.
	*/
	do {
	ok = true;

	if (mode->hdisplay == 800 && mode->vdisplay == 600) {
	/* mode 277 */
	ns->reg_8_shadow &= ~NS2501_8_BPAS;
	DRM_DEBUG_KMS("%s: switching to 800x600\n",
	__FUNCTION__);

	/*
	* No, I do not know where this data comes from.
	* It is just what the video bios left in the DVO, so
	* I'm just copying it here over.
	* This also means that I cannot support any other modes
	* except the ones supported by the bios.
	*/
	ok &= ns2501_writeb(dvo, 0x11, 0xc8); // 0xc7 also works.
	ok &= ns2501_writeb(dvo, 0x1b, 0x19);
	ok &= ns2501_writeb(dvo, 0x1c, 0x62); // VBIOS left 0x64 here, but 0x62 works nicer
	ok &= ns2501_writeb(dvo, 0x1d, 0x02);

	ok &= ns2501_writeb(dvo, 0x34, 0x03);
	ok &= ns2501_writeb(dvo, 0x35, 0xff);

	ok &= ns2501_writeb(dvo, 0x80, 0x27);
	ok &= ns2501_writeb(dvo, 0x81, 0x03);
	ok &= ns2501_writeb(dvo, 0x82, 0x41);
	ok &= ns2501_writeb(dvo, 0x83, 0x05);

	ok &= ns2501_writeb(dvo, 0x8d, 0x02);
	ok &= ns2501_writeb(dvo, 0x8e, 0x04);
	ok &= ns2501_writeb(dvo, 0x8f, 0x00);

	ok &= ns2501_writeb(dvo, 0x90, 0xfe); /* vertical. VBIOS left 0xff here, but 0xfe works better */
	ok &= ns2501_writeb(dvo, 0x91, 0x07);
	ok &= ns2501_writeb(dvo, 0x94, 0x00);
	ok &= ns2501_writeb(dvo, 0x95, 0x00);

	ok &= ns2501_writeb(dvo, 0x96, 0x00);

	ok &= ns2501_writeb(dvo, 0x99, 0x00);
	ok &= ns2501_writeb(dvo, 0x9a, 0x88);

	ok &= ns2501_writeb(dvo, 0x9c, 0x23); /* Looks like first and last line of the image. */
	ok &= ns2501_writeb(dvo, 0x9d, 0x00);
	ok &= ns2501_writeb(dvo, 0x9e, 0x25);
	ok &= ns2501_writeb(dvo, 0x9f, 0x03);

	ok &= ns2501_writeb(dvo, 0xa4, 0x80);

	ok &= ns2501_writeb(dvo, 0xb6, 0x00);

	ok &= ns2501_writeb(dvo, 0xb9, 0xc8); /* horizontal? */
	ok &= ns2501_writeb(dvo, 0xba, 0x00); /* horizontal? */

	ok &= ns2501_writeb(dvo, 0xc0, 0x05); /* horizontal? */
	ok &= ns2501_writeb(dvo, 0xc1, 0xd7);

	ok &= ns2501_writeb(dvo, 0xc2, 0x00);
	ok &= ns2501_writeb(dvo, 0xc3, 0xf8);

	ok &= ns2501_writeb(dvo, 0xc4, 0x03);
	ok &= ns2501_writeb(dvo, 0xc5, 0x1a);

	ok &= ns2501_writeb(dvo, 0xc6, 0x00);
	ok &= ns2501_writeb(dvo, 0xc7, 0x73);
	ok &= ns2501_writeb(dvo, 0xc8, 0x02);

	} else if (mode->hdisplay == 640 && mode->vdisplay == 480) {
	/* mode 274 */
	DRM_DEBUG_KMS("%s: switching to 640x480\n",
	__FUNCTION__);
	/*
	* No, I do not know where this data comes from.
	* It is just what the video bios left in the DVO, so
	* I'm just copying it here over.
	* This also means that I cannot support any other modes
	* except the ones supported by the bios.
	*/
	ns->reg_8_shadow &= ~NS2501_8_BPAS;

	ok &= ns2501_writeb(dvo, 0x11, 0xa0);
	ok &= ns2501_writeb(dvo, 0x1b, 0x11);
	ok &= ns2501_writeb(dvo, 0x1c, 0x54);
	ok &= ns2501_writeb(dvo, 0x1d, 0x03);

	ok &= ns2501_writeb(dvo, 0x34, 0x03);
	ok &= ns2501_writeb(dvo, 0x35, 0xff);

	ok &= ns2501_writeb(dvo, 0x80, 0xff);
	ok &= ns2501_writeb(dvo, 0x81, 0x07);
	ok &= ns2501_writeb(dvo, 0x82, 0x3d);
	ok &= ns2501_writeb(dvo, 0x83, 0x05);

	ok &= ns2501_writeb(dvo, 0x8d, 0x02);
	ok &= ns2501_writeb(dvo, 0x8e, 0x10);
	ok &= ns2501_writeb(dvo, 0x8f, 0x00);

	ok &= ns2501_writeb(dvo, 0x90, 0xff); /* vertical */
	ok &= ns2501_writeb(dvo, 0x91, 0x07);
	ok &= ns2501_writeb(dvo, 0x94, 0x00);
	ok &= ns2501_writeb(dvo, 0x95, 0x00);

	ok &= ns2501_writeb(dvo, 0x96, 0x05);

	ok &= ns2501_writeb(dvo, 0x99, 0x00);
	ok &= ns2501_writeb(dvo, 0x9a, 0x88);

	ok &= ns2501_writeb(dvo, 0x9c, 0x24);
	ok &= ns2501_writeb(dvo, 0x9d, 0x00);
	ok &= ns2501_writeb(dvo, 0x9e, 0x25);
	ok &= ns2501_writeb(dvo, 0x9f, 0x03);

	ok &= ns2501_writeb(dvo, 0xa4, 0x84);

	ok &= ns2501_writeb(dvo, 0xb6, 0x09);

	ok &= ns2501_writeb(dvo, 0xb9, 0xa0); /* horizontal? */
	ok &= ns2501_writeb(dvo, 0xba, 0x00); /* horizontal? */

	ok &= ns2501_writeb(dvo, 0xc0, 0x05); /* horizontal? */
	ok &= ns2501_writeb(dvo, 0xc1, 0x90);

	ok &= ns2501_writeb(dvo, 0xc2, 0x00);
	ok &= ns2501_writeb(dvo, 0xc3, 0x0f);

	ok &= ns2501_writeb(dvo, 0xc4, 0x03);
	ok &= ns2501_writeb(dvo, 0xc5, 0x16);

	ok &= ns2501_writeb(dvo, 0xc6, 0x00);
	ok &= ns2501_writeb(dvo, 0xc7, 0x02);
	ok &= ns2501_writeb(dvo, 0xc8, 0x02);

	} else if (mode->hdisplay == 1024 && mode->vdisplay == 768) {
	/* mode 280 */
	DRM_DEBUG_KMS("%s: switching to 1024x768\n",
	__FUNCTION__);
	/*
	* This might or might not work, actually. I'm silently
	* assuming here that the native panel resolution is
	* 1024x768. If not, then this leaves the scaler disabled
	* generating a picture that is likely not the expected.
	*
	* Problem is that I do not know where to take the panel
	* dimensions from.
	*
	* Enable the bypass, scaling not required.
	*
	* The scaler registers are irrelevant here....
	*
	*/
	ns->reg_8_shadow \|= NS2501_8_BPAS;
	ok &= ns2501_writeb(dvo, 0x37, 0x44);
	} else {
	/*
	* Data not known. Bummer!
	* Hopefully, the code should not go here
	* as mode_OK delivered no other modes.
	*/
	ns->reg_8_shadow \|= NS2501_8_BPAS;
	}
	ok &= ns2501_writeb(dvo, NS2501_REG8, ns->reg_8_shadow);
	} while (!ok && retries--);
	}

	/* set the NS2501 power state */
	static bool ns2501_get_hw_state(struct intel_dvo_device *dvo)
	{
	unsigned char ch;

	if (!ns2501_readb(dvo, NS2501_REG8, &ch))
	return false;

	if (ch & NS2501_8_PD)
	return true;
	else
	return false;
	}

	/* set the NS2501 power state */
	static void ns2501_dpms(struct intel_dvo_device *dvo, bool enable)
	{
	bool ok;
	int retries = 10;
	struct ns2501_priv ns = (struct ns2501_priv )(dvo->dev_priv);
	unsigned char ch;

	DRM_DEBUG_KMS("%s: Trying set the dpms of the DVO to %i\n",
	__FUNCTION__, enable);

	ch = ns->reg_8_shadow;

	if (enable)
	ch \|= NS2501_8_PD;
	else
	ch &= ~NS2501_8_PD;

	if (ns->reg_8_set == 0 \|\| ns->reg_8_shadow != ch) {
	ns->reg_8_set = 1;
	ns->reg_8_shadow = ch;

	do {
	ok = true;
	ok &= ns2501_writeb(dvo, NS2501_REG8, ch);
	ok &=
	ns2501_writeb(dvo, 0x34,
	enable ? 0x03 : 0x00);
	ok &=
	ns2501_writeb(dvo, 0x35,
	enable ? 0xff : 0x00);
	} while (!ok && retries--);
	}
	}

	static void ns2501_dump_regs(struct intel_dvo_device *dvo)
	{
	uint8_t val;

	ns2501_readb(dvo, NS2501_FREQ_LO, &val);
	DRM_LOG_KMS("NS2501_FREQ_LO: 0x%02x\n", val);
	ns2501_readb(dvo, NS2501_FREQ_HI, &val);
	DRM_LOG_KMS("NS2501_FREQ_HI: 0x%02x\n", val);
	ns2501_readb(dvo, NS2501_REG8, &val);
	DRM_LOG_KMS("NS2501_REG8: 0x%02x\n", val);
	ns2501_readb(dvo, NS2501_REG9, &val);
	DRM_LOG_KMS("NS2501_REG9: 0x%02x\n", val);
	ns2501_readb(dvo, NS2501_REGC, &val);
	DRM_LOG_KMS("NS2501_REGC: 0x%02x\n", val);
	}

	static void ns2501_destroy(struct intel_dvo_device *dvo)
	{
	struct ns2501_priv *ns = dvo->dev_priv;

	if (ns) {
	kfree(ns);
	dvo->dev_priv = NULL;
	}
	}

	struct intel_dvo_dev_ops ns2501_ops = {
	.init = ns2501_init,
	.detect = ns2501_detect,
	.mode_valid = ns2501_mode_valid,
	.mode_set = ns2501_mode_set,
	.dpms = ns2501_dpms,
	.get_hw_state = ns2501_get_hw_state,
	.dump_regs = ns2501_dump_regs,
	.destroy = ns2501_destroy,
	};