drivers/gpu/drm/nouveau/nouveau_i2c.c - SHIFTPHONES/kernel/common - Gitiles

 /*
  * Copyright 2009 Red Hat Inc.
  *
  * 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, sublicense,
  * 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 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 NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
  *
  * Authors: Ben Skeggs
  */

 #include <linux/module.h>

 #include "drmP.h"
 #include "nouveau_drv.h"
 #include "nouveau_i2c.h"
 #include "nouveau_hw.h"

 static void
 i2c_drive_scl(void *data, int state)
 {
 	struct nouveau_i2c_chan *port = data;
 	if (port->type == 0) {
 		u8 val = NVReadVgaCrtc(port->dev, 0, port->drive);
 		if (state) val |= 0x20;
 		else	   val &= 0xdf;
 		NVWriteVgaCrtc(port->dev, 0, port->drive, val | 0x01);
 	} else
 	if (port->type == 4) {
 		nv_mask(port->dev, port->drive, 0x2f, state ? 0x21 : 0x01);
 	} else
 	if (port->type == 5) {
 		if (state) port->state |= 0x01;
 		else	   port->state &= 0xfe;
 		nv_wr32(port->dev, port->drive, 4 | port->state);
 	}
 }

 static void
 i2c_drive_sda(void *data, int state)
 {
 	struct nouveau_i2c_chan *port = data;
 	if (port->type == 0) {
 		u8 val = NVReadVgaCrtc(port->dev, 0, port->drive);
 		if (state) val |= 0x10;
 		else	   val &= 0xef;
 		NVWriteVgaCrtc(port->dev, 0, port->drive, val | 0x01);
 	} else
 	if (port->type == 4) {
 		nv_mask(port->dev, port->drive, 0x1f, state ? 0x11 : 0x01);
 	} else
 	if (port->type == 5) {
 		if (state) port->state |= 0x02;
 		else	   port->state &= 0xfd;
 		nv_wr32(port->dev, port->drive, 4 | port->state);
 	}
 }

 static int
 i2c_sense_scl(void *data)
 {
 	struct nouveau_i2c_chan *port = data;
 	struct drm_nouveau_private *dev_priv = port->dev->dev_private;
 	if (port->type == 0) {
 		return !!(NVReadVgaCrtc(port->dev, 0, port->sense) & 0x04);
 	} else
 	if (port->type == 4) {
 		return !!(nv_rd32(port->dev, port->sense) & 0x00040000);
 	} else
 	if (port->type == 5) {
 		if (dev_priv->card_type < NV_D0)
 			return !!(nv_rd32(port->dev, port->sense) & 0x01);
 		else
 			return !!(nv_rd32(port->dev, port->sense) & 0x10);
 	}
 	return 0;
 }

 static int
 i2c_sense_sda(void *data)
 {
 	struct nouveau_i2c_chan *port = data;
 	struct drm_nouveau_private *dev_priv = port->dev->dev_private;
 	if (port->type == 0) {
 		return !!(NVReadVgaCrtc(port->dev, 0, port->sense) & 0x08);
 	} else
 	if (port->type == 4) {
 		return !!(nv_rd32(port->dev, port->sense) & 0x00080000);
 	} else
 	if (port->type == 5) {
 		if (dev_priv->card_type < NV_D0)
 			return !!(nv_rd32(port->dev, port->sense) & 0x02);
 		else
 			return !!(nv_rd32(port->dev, port->sense) & 0x20);
 	}
 	return 0;
 }

 static const uint32_t nv50_i2c_port[] = {
 	0x00e138, 0x00e150, 0x00e168, 0x00e180,
 	0x00e254, 0x00e274, 0x00e764, 0x00e780,
 	0x00e79c, 0x00e7b8
 };

 static u8 *
 i2c_table(struct drm_device *dev, u8 *version)
 {
 	u8 *dcb = dcb_table(dev), *i2c = NULL;
 	if (dcb) {
 		if (dcb[0] >= 0x15)
 			i2c = ROMPTR(dev, dcb[2]);
 		if (dcb[0] >= 0x30)
 			i2c = ROMPTR(dev, dcb[4]);
 	}

 	/* early revisions had no version number, use dcb version */
 	if (i2c) {
 		*version = dcb[0];
 		if (*version >= 0x30)
 			*version = i2c[0];
 	}

 	return i2c;
 }

 int
 nouveau_i2c_init(struct drm_device *dev)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nvbios *bios = &dev_priv->vbios;
 	struct nouveau_i2c_chan *port;
 	u8 version = 0x00, entries, recordlen;
 	u8 *i2c, *entry, legacy[2][4] = {};
 	int ret, i;

 	INIT_LIST_HEAD(&dev_priv->i2c_ports);

 	i2c = i2c_table(dev, &version);
 	if (!i2c) {
 		u8 *bmp = &bios->data[bios->offset];
 		if (bios->type != NVBIOS_BMP)
 			return -ENODEV;

 		legacy[0][0] = NV_CIO_CRE_DDC_WR__INDEX;
 		legacy[0][1] = NV_CIO_CRE_DDC_STATUS__INDEX;
 		legacy[1][0] = NV_CIO_CRE_DDC0_WR__INDEX;
 		legacy[1][1] = NV_CIO_CRE_DDC0_STATUS__INDEX;

 		/* BMP (from v4.0) has i2c info in the structure, it's in a
 		 * fixed location on earlier VBIOS
 		 */
 		if (bmp[5] < 4)
 			i2c = &bios->data[0x48];
 		else
 			i2c = &bmp[0x36];

 		if (i2c[4]) legacy[0][0] = i2c[4];
 		if (i2c[5]) legacy[0][1] = i2c[5];
 		if (i2c[6]) legacy[1][0] = i2c[6];
 		if (i2c[7]) legacy[1][1] = i2c[7];
 	}

 	if (version >= 0x30) {
 		entry     = i2c[1] + i2c;
 		entries   = i2c[2];
 		recordlen = i2c[3];
 	} else
 	if (version) {
 		entry     = i2c;
 		entries   = 16;
 		recordlen = 4;
 	} else {
 		entry     = legacy[0];
 		entries   = 2;
 		recordlen = 4;
 	}

 	for (i = 0; i < entries; i++, entry += recordlen) {
 		port = kzalloc(sizeof(*port), GFP_KERNEL);
 		if (port == NULL) {
 			nouveau_i2c_fini(dev);
 			return -ENOMEM;
 		}

 		port->type = entry[3];
 		if (version < 0x30) {
 			port->type &= 0x07;
 			if (port->type == 0x07)
 				port->type = 0xff;
 		}

 		if (port->type == 0xff) {
 			kfree(port);
 			continue;
 		}

 		switch (port->type) {
 		case 0: /* NV04:NV50 */
 			port->drive = entry[0];
 			port->sense = entry[1];
 			break;
 		case 4: /* NV4E */
 			port->drive = 0x600800 + entry[1];
 			port->sense = port->drive;
 			break;
 		case 5: /* NV50- */
 			port->drive = entry[0] & 0x0f;
 			if (dev_priv->card_type < NV_D0) {
 				if (port->drive >= ARRAY_SIZE(nv50_i2c_port))
 					break;
 				port->drive = nv50_i2c_port[port->drive];
 				port->sense = port->drive;
 			} else {
 				port->drive = 0x00d014 + (port->drive * 0x20);
 				port->sense = port->drive;
 			}
 			break;
 		case 6: /* NV50- DP AUX */
 			port->drive = entry[0];
 			port->sense = port->drive;
 			port->adapter.algo = &nouveau_dp_i2c_algo;
 			break;
 		default:
 			break;
 		}

 		if (!port->adapter.algo && !port->drive) {
 			NV_ERROR(dev, "I2C%d: type %d index %x/%x unknown\n",
 				 i, port->type, port->drive, port->sense);
 			kfree(port);
 			continue;
 		}

 		snprintf(port->adapter.name, sizeof(port->adapter.name),
 			 "nouveau-%s-%d", pci_name(dev->pdev), i);
 		port->adapter.owner = THIS_MODULE;
 		port->adapter.dev.parent = &dev->pdev->dev;
 		port->dev = dev;
 		port->index = i;
 		port->dcb = ROM32(entry[0]);
 		i2c_set_adapdata(&port->adapter, i2c);

 		if (port->adapter.algo != &nouveau_dp_i2c_algo) {
 			port->adapter.algo_data = &port->bit;
 			port->bit.udelay = 10;
 			port->bit.timeout = usecs_to_jiffies(2200);
 			port->bit.data = port;
 			port->bit.setsda = i2c_drive_sda;
 			port->bit.setscl = i2c_drive_scl;
 			port->bit.getsda = i2c_sense_sda;
 			port->bit.getscl = i2c_sense_scl;

 			i2c_drive_scl(port, 0);
 			i2c_drive_sda(port, 1);
 			i2c_drive_scl(port, 1);

 			ret = i2c_bit_add_bus(&port->adapter);
 		} else {
 			port->adapter.algo = &nouveau_dp_i2c_algo;
 			ret = i2c_add_adapter(&port->adapter);
 		}

 		if (ret) {
 			NV_ERROR(dev, "I2C%d: failed register: %d\n", i, ret);
 			kfree(port);
 			continue;
 		}

 		list_add_tail(&port->head, &dev_priv->i2c_ports);
 	}

 	return 0;
 }

 void
 nouveau_i2c_fini(struct drm_device *dev)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_i2c_chan *port, *tmp;

 	list_for_each_entry_safe(port, tmp, &dev_priv->i2c_ports, head) {
 		i2c_del_adapter(&port->adapter);
 		kfree(port);
 	}
 }

 struct nouveau_i2c_chan *
 nouveau_i2c_find(struct drm_device *dev, u8 index)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_i2c_chan *port;

 	if (index == NV_I2C_DEFAULT(0) ||
 	    index == NV_I2C_DEFAULT(1)) {
 		u8 version, *i2c = i2c_table(dev, &version);
 		if (i2c && version >= 0x30) {
 			if (index == NV_I2C_DEFAULT(0))
 				index = (i2c[4] & 0x0f);
 			else
 				index = (i2c[4] & 0xf0) >> 4;
 		} else {
 			index = 2;
 		}
 	}

 	list_for_each_entry(port, &dev_priv->i2c_ports, head) {
 		if (port->index == index)
 			break;
 	}

 	if (&port->head == &dev_priv->i2c_ports)
 		return NULL;

 	if (dev_priv->card_type >= NV_50 && (port->dcb & 0x00000100)) {
 		u32 reg = 0x00e500, val;
 		if (port->type == 6) {
 			reg += port->drive * 0x50;
 			val  = 0x2002;
 		} else {
 			reg += ((port->dcb & 0x1e00) >> 9) * 0x50;
 			val  = 0xe001;
 		}

 		/* nfi, but neither auxch or i2c work if it's 1 */
 		nv_mask(dev, reg + 0x0c, 0x00000001, 0x00000000);
 		/* nfi, but switches auxch vs normal i2c */
 		nv_mask(dev, reg + 0x00, 0x0000f003, val);
 	}

 	return port;
 }

 bool
 nouveau_probe_i2c_addr(struct nouveau_i2c_chan *i2c, int addr)
 {
 	uint8_t buf[] = { 0 };
 	struct i2c_msg msgs[] = {
 		{
 			.addr = addr,
 			.flags = 0,
 			.len = 1,
 			.buf = buf,
 		},
 		{
 			.addr = addr,
 			.flags = I2C_M_RD,
 			.len = 1,
 			.buf = buf,
 		}
 	};

 	return i2c_transfer(&i2c->adapter, msgs, 2) == 2;
 }

 int
 nouveau_i2c_identify(struct drm_device *dev, const char *what,
 		     struct i2c_board_info *info,
 		     bool (*match)(struct nouveau_i2c_chan *,
 				   struct i2c_board_info *),
 		     int index)
 {
 	struct nouveau_i2c_chan *i2c = nouveau_i2c_find(dev, index);
 	int i;

 	if (!i2c) {
 		NV_DEBUG(dev, "No bus when probing %s on %d\n", what, index);
 		return -ENODEV;
 	}

 	NV_DEBUG(dev, "Probing %ss on I2C bus: %d\n", what, i2c->index);
 	for (i = 0; info[i].addr; i++) {
 		if (nouveau_probe_i2c_addr(i2c, info[i].addr) &&
 		    (!match || match(i2c, &info[i]))) {
 			NV_INFO(dev, "Detected %s: %s\n", what, info[i].type);
 			return i;
 		}
 	}

 	NV_DEBUG(dev, "No devices found.\n");
 	return -ENODEV;
 }
	/*
	* Copyright 2009 Red Hat Inc.
	*
	* 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, sublicense,
	* 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 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 NONINFRINGEMENT. IN NO EVENT SHALL
	* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
	*
	* Authors: Ben Skeggs
	*/

	#include <linux/module.h>

	#include "drmP.h"
	#include "nouveau_drv.h"
	#include "nouveau_i2c.h"
	#include "nouveau_hw.h"

	static void
	i2c_drive_scl(void *data, int state)
	{
	struct nouveau_i2c_chan *port = data;
	if (port->type == 0) {
	u8 val = NVReadVgaCrtc(port->dev, 0, port->drive);
	if (state) val \|= 0x20;
	else val &= 0xdf;
	NVWriteVgaCrtc(port->dev, 0, port->drive, val \| 0x01);
	} else
	if (port->type == 4) {
	nv_mask(port->dev, port->drive, 0x2f, state ? 0x21 : 0x01);
	} else
	if (port->type == 5) {
	if (state) port->state \|= 0x01;
	else port->state &= 0xfe;
	nv_wr32(port->dev, port->drive, 4 \| port->state);
	}
	}

	static void
	i2c_drive_sda(void *data, int state)
	{
	struct nouveau_i2c_chan *port = data;
	if (port->type == 0) {
	u8 val = NVReadVgaCrtc(port->dev, 0, port->drive);
	if (state) val \|= 0x10;
	else val &= 0xef;
	NVWriteVgaCrtc(port->dev, 0, port->drive, val \| 0x01);
	} else
	if (port->type == 4) {
	nv_mask(port->dev, port->drive, 0x1f, state ? 0x11 : 0x01);
	} else
	if (port->type == 5) {
	if (state) port->state \|= 0x02;
	else port->state &= 0xfd;
	nv_wr32(port->dev, port->drive, 4 \| port->state);
	}
	}

	static int
	i2c_sense_scl(void *data)
	{
	struct nouveau_i2c_chan *port = data;
	struct drm_nouveau_private *dev_priv = port->dev->dev_private;
	if (port->type == 0) {
	return !!(NVReadVgaCrtc(port->dev, 0, port->sense) & 0x04);
	} else
	if (port->type == 4) {
	return !!(nv_rd32(port->dev, port->sense) & 0x00040000);
	} else
	if (port->type == 5) {
	if (dev_priv->card_type < NV_D0)
	return !!(nv_rd32(port->dev, port->sense) & 0x01);
	else
	return !!(nv_rd32(port->dev, port->sense) & 0x10);
	}
	return 0;
	}

	static int
	i2c_sense_sda(void *data)
	{
	struct nouveau_i2c_chan *port = data;
	struct drm_nouveau_private *dev_priv = port->dev->dev_private;
	if (port->type == 0) {
	return !!(NVReadVgaCrtc(port->dev, 0, port->sense) & 0x08);
	} else
	if (port->type == 4) {
	return !!(nv_rd32(port->dev, port->sense) & 0x00080000);
	} else
	if (port->type == 5) {
	if (dev_priv->card_type < NV_D0)
	return !!(nv_rd32(port->dev, port->sense) & 0x02);
	else
	return !!(nv_rd32(port->dev, port->sense) & 0x20);
	}
	return 0;
	}

	static const uint32_t nv50_i2c_port[] = {
	0x00e138, 0x00e150, 0x00e168, 0x00e180,
	0x00e254, 0x00e274, 0x00e764, 0x00e780,
	0x00e79c, 0x00e7b8
	};

	static u8 *
	i2c_table(struct drm_device dev, u8 version)
	{
	u8 dcb = dcb_table(dev), i2c = NULL;
	if (dcb) {
	if (dcb[0] >= 0x15)
	i2c = ROMPTR(dev, dcb[2]);
	if (dcb[0] >= 0x30)
	i2c = ROMPTR(dev, dcb[4]);
	}

	/* early revisions had no version number, use dcb version */
	if (i2c) {
	*version = dcb[0];
	if (*version >= 0x30)
	*version = i2c[0];
	}

	return i2c;
	}

	int
	nouveau_i2c_init(struct drm_device *dev)
	{
	struct drm_nouveau_private *dev_priv = dev->dev_private;
	struct nvbios *bios = &dev_priv->vbios;
	struct nouveau_i2c_chan *port;
	u8 version = 0x00, entries, recordlen;
	u8 i2c, entry, legacy[2][4] = {};
	int ret, i;

	INIT_LIST_HEAD(&dev_priv->i2c_ports);

	i2c = i2c_table(dev, &version);
	if (!i2c) {
	u8 *bmp = &bios->data[bios->offset];
	if (bios->type != NVBIOS_BMP)
	return -ENODEV;

	legacy[0][0] = NV_CIO_CRE_DDC_WR__INDEX;
	legacy[0][1] = NV_CIO_CRE_DDC_STATUS__INDEX;
	legacy[1][0] = NV_CIO_CRE_DDC0_WR__INDEX;
	legacy[1][1] = NV_CIO_CRE_DDC0_STATUS__INDEX;

	/* BMP (from v4.0) has i2c info in the structure, it's in a
	* fixed location on earlier VBIOS
	*/
	if (bmp[5] < 4)
	i2c = &bios->data[0x48];
	else
	i2c = &bmp[0x36];

	if (i2c[4]) legacy[0][0] = i2c[4];
	if (i2c[5]) legacy[0][1] = i2c[5];
	if (i2c[6]) legacy[1][0] = i2c[6];
	if (i2c[7]) legacy[1][1] = i2c[7];
	}

	if (version >= 0x30) {
	entry = i2c[1] + i2c;
	entries = i2c[2];
	recordlen = i2c[3];
	} else
	if (version) {
	entry = i2c;
	entries = 16;
	recordlen = 4;
	} else {
	entry = legacy[0];
	entries = 2;
	recordlen = 4;
	}

	for (i = 0; i < entries; i++, entry += recordlen) {
	port = kzalloc(sizeof(*port), GFP_KERNEL);
	if (port == NULL) {
	nouveau_i2c_fini(dev);
	return -ENOMEM;
	}

	port->type = entry[3];
	if (version < 0x30) {
	port->type &= 0x07;
	if (port->type == 0x07)
	port->type = 0xff;
	}

	if (port->type == 0xff) {
	kfree(port);
	continue;
	}

	switch (port->type) {
	case 0: /* NV04:NV50 */
	port->drive = entry[0];
	port->sense = entry[1];
	break;
	case 4: /* NV4E */
	port->drive = 0x600800 + entry[1];
	port->sense = port->drive;
	break;
	case 5: /* NV50- */
	port->drive = entry[0] & 0x0f;
	if (dev_priv->card_type < NV_D0) {
	if (port->drive >= ARRAY_SIZE(nv50_i2c_port))
	break;
	port->drive = nv50_i2c_port[port->drive];
	port->sense = port->drive;
	} else {
	port->drive = 0x00d014 + (port->drive * 0x20);
	port->sense = port->drive;
	}
	break;
	case 6: /* NV50- DP AUX */
	port->drive = entry[0];
	port->sense = port->drive;
	port->adapter.algo = &nouveau_dp_i2c_algo;
	break;
	default:
	break;
	}

	if (!port->adapter.algo && !port->drive) {
	NV_ERROR(dev, "I2C%d: type %d index %x/%x unknown\n",
	i, port->type, port->drive, port->sense);
	kfree(port);
	continue;
	}

	snprintf(port->adapter.name, sizeof(port->adapter.name),
	"nouveau-%s-%d", pci_name(dev->pdev), i);
	port->adapter.owner = THIS_MODULE;
	port->adapter.dev.parent = &dev->pdev->dev;
	port->dev = dev;
	port->index = i;
	port->dcb = ROM32(entry[0]);
	i2c_set_adapdata(&port->adapter, i2c);

	if (port->adapter.algo != &nouveau_dp_i2c_algo) {
	port->adapter.algo_data = &port->bit;
	port->bit.udelay = 10;
	port->bit.timeout = usecs_to_jiffies(2200);
	port->bit.data = port;
	port->bit.setsda = i2c_drive_sda;
	port->bit.setscl = i2c_drive_scl;
	port->bit.getsda = i2c_sense_sda;
	port->bit.getscl = i2c_sense_scl;

	i2c_drive_scl(port, 0);
	i2c_drive_sda(port, 1);
	i2c_drive_scl(port, 1);

	ret = i2c_bit_add_bus(&port->adapter);
	} else {
	port->adapter.algo = &nouveau_dp_i2c_algo;
	ret = i2c_add_adapter(&port->adapter);
	}

	if (ret) {
	NV_ERROR(dev, "I2C%d: failed register: %d\n", i, ret);
	kfree(port);
	continue;
	}

	list_add_tail(&port->head, &dev_priv->i2c_ports);
	}

	return 0;
	}

	void
	nouveau_i2c_fini(struct drm_device *dev)
	{
	struct drm_nouveau_private *dev_priv = dev->dev_private;
	struct nouveau_i2c_chan port, tmp;

	list_for_each_entry_safe(port, tmp, &dev_priv->i2c_ports, head) {
	i2c_del_adapter(&port->adapter);
	kfree(port);
	}
	}

	struct nouveau_i2c_chan *
	nouveau_i2c_find(struct drm_device *dev, u8 index)
	{
	struct drm_nouveau_private *dev_priv = dev->dev_private;
	struct nouveau_i2c_chan *port;

	if (index == NV_I2C_DEFAULT(0) \|\|
	index == NV_I2C_DEFAULT(1)) {
	u8 version, *i2c = i2c_table(dev, &version);
	if (i2c && version >= 0x30) {
	if (index == NV_I2C_DEFAULT(0))
	index = (i2c[4] & 0x0f);
	else
	index = (i2c[4] & 0xf0) >> 4;
	} else {
	index = 2;
	}
	}

	list_for_each_entry(port, &dev_priv->i2c_ports, head) {
	if (port->index == index)
	break;
	}

	if (&port->head == &dev_priv->i2c_ports)
	return NULL;

	if (dev_priv->card_type >= NV_50 && (port->dcb & 0x00000100)) {
	u32 reg = 0x00e500, val;
	if (port->type == 6) {
	reg += port->drive * 0x50;
	val = 0x2002;
	} else {
	reg += ((port->dcb & 0x1e00) >> 9) * 0x50;
	val = 0xe001;
	}

	/* nfi, but neither auxch or i2c work if it's 1 */
	nv_mask(dev, reg + 0x0c, 0x00000001, 0x00000000);
	/* nfi, but switches auxch vs normal i2c */
	nv_mask(dev, reg + 0x00, 0x0000f003, val);
	}

	return port;
	}

	bool
	nouveau_probe_i2c_addr(struct nouveau_i2c_chan *i2c, int addr)
	{
	uint8_t buf[] = { 0 };
	struct i2c_msg msgs[] = {
	{
	.addr = addr,
	.flags = 0,
	.len = 1,
	.buf = buf,
	},
	{
	.addr = addr,
	.flags = I2C_M_RD,
	.len = 1,
	.buf = buf,
	}
	};

	return i2c_transfer(&i2c->adapter, msgs, 2) == 2;
	}

	int
	nouveau_i2c_identify(struct drm_device dev, const char what,
	struct i2c_board_info *info,
	bool (match)(struct nouveau_i2c_chan ,
	struct i2c_board_info *),
	int index)
	{
	struct nouveau_i2c_chan *i2c = nouveau_i2c_find(dev, index);
	int i;

	if (!i2c) {
	NV_DEBUG(dev, "No bus when probing %s on %d\n", what, index);
	return -ENODEV;
	}

	NV_DEBUG(dev, "Probing %ss on I2C bus: %d\n", what, i2c->index);
	for (i = 0; info[i].addr; i++) {
	if (nouveau_probe_i2c_addr(i2c, info[i].addr) &&
	(!match \|\| match(i2c, &info[i]))) {
	NV_INFO(dev, "Detected %s: %s\n", what, info[i].type);
	return i;
	}
	}

	NV_DEBUG(dev, "No devices found.\n");
	return -ENODEV;
	}