[PATCH V4] drm: edid: add support for E-DDC

[PATCH V4] drm: edid: add support for E-DDC

[Shirish S]

This patch adds support in probing 4 block edid data, for E-DDC.
This is the first test case in CTS, for HDMI compliance.

Changes from V3:
Remove switch,and avoid sending of segment data for non E-DDC

Based on drm-next branch

Shirish S (1):
  drm: edid: add support for E-DDC

 drivers/gpu/drm/drm_edid.c |   22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

[PATCH V4] drm: edid: add support for E-DDC

[Shirish S]

The current logic for probing ddc is limited to
2 blocks (256 bytes), this patch adds support
for the 4 block (512) data.

To do this, a single 8-bit segment index is
passed to the display via the I2C address 30h.
Data from the selected segment is then immediately
read via the regular DDC2 address using a repeated
I2C 'START' signal.

Signed-off-by: Shirish S <s.shirish@samsung.com>
---
 drivers/gpu/drm/drm_edid.c |   22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index a8743c3..cde7af0 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
 		      int block, int len)
 {
 	unsigned char start = block * EDID_LENGTH;
+	unsigned char segment = block >> 1;
+	unsigned char xfers = segment ? 3 : 2;
 	int ret, retries = 5;
 
 	/* The core i2c driver will automatically retry the transfer if the
@@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
 	 */
 	do {
 		struct i2c_msg msgs[] = {
-			{
+			{ /*set segment pointer */
+				.addr	= DDC_SEGMENT_ADDR,
+				.flags	= segment ? 0 : I2C_M_IGNORE_NAK,
+				.len	= 1,
+				.buf	= &segment,
+			}, {
 				.addr	= DDC_ADDR,
 				.flags	= 0,
 				.len	= 1,
@@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
 				.buf	= buf,
 			}
 		};
-		ret = i2c_transfer(adapter, msgs, 2);
+	/* Avoid sending the segment addr to not upset non-compliant ddc
+	 * monitors.
+	 */
+		if (!segment)
+			ret = i2c_transfer(adapter, &msgs[1], xfers);
+		else
+			ret = i2c_transfer(adapter, msgs, xfers);
+
 		if (ret == -ENXIO) {
 			DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
 					adapter->name);
 			break;
 		}
-	} while (ret != 2 && --retries);
+	} while (ret != xfers && --retries);
 
-	return ret == 2 ? 0 : -1;
+	return ret == xfers ? 0 : -1;
 }
 
 static bool drm_edid_is_zero(u8 *in_edid, int length)
-- 
1.7.0.4

Re: [PATCH V4] drm: edid: add support for E-DDC

[Daniel Vetter]

On Sat, Aug 25, 2012 at 03:13:56PM +0530, Shirish S wrote:
> The current logic for probing ddc is limited to
> 2 blocks (256 bytes), this patch adds support
> for the 4 block (512) data.
> 
> To do this, a single 8-bit segment index is
> passed to the display via the I2C address 30h.
> Data from the selected segment is then immediately
> read via the regular DDC2 address using a repeated
> I2C 'START' signal.
> 
> Signed-off-by: Shirish S <s.shirish@samsung.com>

Looks good.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_edid.c |   22 ++++++++++++++++++----
>  1 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index a8743c3..cde7af0 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  		      int block, int len)
>  {
>  	unsigned char start = block * EDID_LENGTH;
> +	unsigned char segment = block >> 1;
> +	unsigned char xfers = segment ? 3 : 2;
>  	int ret, retries = 5;
>  
>  	/* The core i2c driver will automatically retry the transfer if the
> @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  	 */
>  	do {
>  		struct i2c_msg msgs[] = {
> -			{
> +			{ /*set segment pointer */
> +				.addr	= DDC_SEGMENT_ADDR,
> +				.flags	= segment ? 0 : I2C_M_IGNORE_NAK,
> +				.len	= 1,
> +				.buf	= &segment,
> +			}, {
>  				.addr	= DDC_ADDR,
>  				.flags	= 0,
>  				.len	= 1,
> @@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  				.buf	= buf,
>  			}
>  		};
> -		ret = i2c_transfer(adapter, msgs, 2);
> +	/* Avoid sending the segment addr to not upset non-compliant ddc
> +	 * monitors.
> +	 */
> +		if (!segment)
> +			ret = i2c_transfer(adapter, &msgs[1], xfers);
> +		else
> +			ret = i2c_transfer(adapter, msgs, xfers);
> +
>  		if (ret == -ENXIO) {
>  			DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
>  					adapter->name);
>  			break;
>  		}
> -	} while (ret != 2 && --retries);
> +	} while (ret != xfers && --retries);
>  
> -	return ret == 2 ? 0 : -1;
> +	return ret == xfers ? 0 : -1;
>  }
>  
>  static bool drm_edid_is_zero(u8 *in_edid, int length)
> -- 
> 1.7.0.4
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48

Re: [PATCH V4] drm: edid: add support for E-DDC

[Ville Syrjälä]

On Sat, Aug 25, 2012 at 03:13:56PM +0530, Shirish S wrote:
> The current logic for probing ddc is limited to
> 2 blocks (256 bytes), this patch adds support
> for the 4 block (512) data.
> 
> To do this, a single 8-bit segment index is
> passed to the display via the I2C address 30h.
> Data from the selected segment is then immediately
> read via the regular DDC2 address using a repeated
> I2C 'START' signal.
> 
> Signed-off-by: Shirish S <s.shirish@samsung.com>
> ---
>  drivers/gpu/drm/drm_edid.c |   22 ++++++++++++++++++----
>  1 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index a8743c3..cde7af0 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  		      int block, int len)
>  {
>  	unsigned char start = block * EDID_LENGTH;
> +	unsigned char segment = block >> 1;
> +	unsigned char xfers = segment ? 3 : 2;
>  	int ret, retries = 5;
>  
>  	/* The core i2c driver will automatically retry the transfer if the
> @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  	 */
>  	do {
>  		struct i2c_msg msgs[] = {
> -			{
> +			{ /*set segment pointer */

Missing whitespace after '/*'. Perhaps just drop the comment. I don't
see much value in it.

> +				.addr	= DDC_SEGMENT_ADDR,
> +				.flags	= segment ? 0 : I2C_M_IGNORE_NAK,
> +				.len	= 1,
> +				.buf	= &segment,
> +			}, {
>  				.addr	= DDC_ADDR,
>  				.flags	= 0,
>  				.len	= 1,
> @@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf,
>  				.buf	= buf,
>  			}
>  		};
> -		ret = i2c_transfer(adapter, msgs, 2);
> +	/* Avoid sending the segment addr to not upset non-compliant ddc
> +	 * monitors.
> +	 */

Wrong indentation and comment style is wrong. I'm guessing this didn't go
through checkpatch.pl.

Otherwise looks OK to me.

-- 
Ville Syrjälä
Intel OTC

Re: [PATCH V4] drm: edid: add support for E-DDC

[Jean Delvare]

Hi all,

Sorry for breaking message threading but I was not included in
iterations 3 and 4 of this patch.

Random comments about v4:

> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned 
> char *buf,
>                       int block, int len)
>  {
>         unsigned char start = block * EDID_LENGTH;
> +       unsigned char segment = block >> 1;
> +       unsigned char xfers = segment ? 3 : 2;
>         int ret, retries = 5;
>  
>         /* The core i2c driver will automatically retry the transfer if the
> @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, 
> unsigned char *buf,
>          */
>         do {
>                 struct i2c_msg msgs[] = {
> -                       {
> +                       { /*set segment pointer */
> +                               .addr   = DDC_SEGMENT_ADDR,
> +                               .flags  = segment ? 0 : I2C_M_IGNORE_NAK,

I don't get the idea. If segment == 0, this message is never sent, so the
value of field flags doesn't matter. So flags will always be 0 when this
message is sent, so it can be hard-coded.

But from previous discussions my understanding was an agreement on always
using I2C_M_IGNORE_NAK for improved compatibility. So I2C_M_IGNORE_NAK
should be hard-coded, not 0?

> +                               .len    = 1,
> +                               .buf    = &segment,
> +                       }, {
>                                 .addr   = DDC_ADDR,
>                                 .flags  = 0,
>                                 .len    = 1,
> @@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, 
> unsigned char *buf,
>                                 .buf    = buf,
>                         }
>                 };
> -               ret = i2c_transfer(adapter, msgs, 2);
> +       /* Avoid sending the segment addr to not upset non-compliant ddc
> +        * monitors.
> +        */

s/segment addr/segment/, plus it's abot E-DCC compliance as I understand it,
not DDC.

> +               if (!segment)
> +                       ret = i2c_transfer(adapter, &msgs[1], xfers);
> +               else
> +                       ret = i2c_transfer(adapter, msgs, xfers);
> +

This can be written:

		ret = i2c_transfer(adapter, &msgs[3 - xfers], xfers);

Which is more compact and, I suspect, faster.

>                 if (ret == -ENXIO) {
>                         DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",
>                                         adapter->name);
>                         break;
>                 }
> -       } while (ret != 2 && --retries);
> +       } while (ret != xfers && --retries);
>  
> -       return ret == 2 ? 0 : -1;
> +       return ret == xfers ? 0 : -1;
>  }
>  
>  static bool drm_edid_is_zero(u8 *in_edid, int length)

Other than this, your code looks reasonable, not so different from what
I submitted 8 months ago actually. But ISTU you can test the code with
real hardware while I couldn't.

With the changes above applied, you can add:

Reviewed-by: Jean Delvare <jdelvare@suse.de>

-- 
Jean Delvare
Suse L3

Re: [PATCH V4] drm: edid: add support for E-DDC

[Shirish S]

[-- Attachment #1.1: Type: text/plain, Size: 3013 bytes --]

On Wed, Aug 29, 2012 at 4:08 AM, Ville Syrjälä <
ville.syrjala@linux.intel.com> wrote:

> On Sat, Aug 25, 2012 at 03:13:56PM +0530, Shirish S wrote:
> > The current logic for probing ddc is limited to
> > 2 blocks (256 bytes), this patch adds support
> > for the 4 block (512) data.
> >
> > To do this, a single 8-bit segment index is
> > passed to the display via the I2C address 30h.
> > Data from the selected segment is then immediately
> > read via the regular DDC2 address using a repeated
> > I2C 'START' signal.
> >
> > Signed-off-by: Shirish S <s.shirish@samsung.com>
> > ---
> >  drivers/gpu/drm/drm_edid.c |   22 ++++++++++++++++++----
> >  1 files changed, 18 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index a8743c3..cde7af0 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> unsigned char *buf,
> >                     int block, int len)
> >  {
> >       unsigned char start = block * EDID_LENGTH;
> > +     unsigned char segment = block >> 1;
> > +     unsigned char xfers = segment ? 3 : 2;
> >       int ret, retries = 5;
> >
> >       /* The core i2c driver will automatically retry the transfer if the
> > @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> unsigned char *buf,
> >        */
> >       do {
> >               struct i2c_msg msgs[] = {
> > -                     {
> > +                     { /*set segment pointer */
>
> Missing whitespace after '/*'. Perhaps just drop the comment. I don't
> see much value in it.
>
> Done.

> > +                             .addr   = DDC_SEGMENT_ADDR,
> > +                             .flags  = segment ? 0 : I2C_M_IGNORE_NAK,
> > +                             .len    = 1,
> > +                             .buf    = &segment,
> > +                     }, {
> >                               .addr   = DDC_ADDR,
> >                               .flags  = 0,
> >                               .len    = 1,
> > @@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> unsigned char *buf,
> >                               .buf    = buf,
> >                       }
> >               };
> > -             ret = i2c_transfer(adapter, msgs, 2);
> > +     /* Avoid sending the segment addr to not upset non-compliant ddc
> > +      * monitors.
> > +      */
>
> Wrong indentation and comment style is wrong. I'm guessing this didn't go
> through checkpatch.pl.
>
> I never got tha above as either an error or warning in the checkpatch,
anyways have uploaded patch set 5 incorporating your comments.

> Otherwise looks OK to me.
>
> --
> Ville Syrjälä
> Intel OTC
>

- Shirish

> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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Re: [PATCH V4] drm: edid: add support for E-DDC

[Shirish S]

[-- Attachment #1.1: Type: text/plain, Size: 3936 bytes --]

Hi Jean,

On Wed, Aug 29, 2012 at 6:44 AM, Jean Delvare <jdelvare@suse.de> wrote:

> Hi all,
>
> Sorry for breaking message threading but I was not included in
> iterations 3 and 4 of this patch.
>
> Random comments about v4:
>
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> unsigned
> > char *buf,
> >                       int block, int len)
> >  {
> >         unsigned char start = block * EDID_LENGTH;
> > +       unsigned char segment = block >> 1;
> > +       unsigned char xfers = segment ? 3 : 2;
> >         int ret, retries = 5;
> >
> >         /* The core i2c driver will automatically retry the transfer if
> the
> > @@ -264,7 +266,12 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> > unsigned char *buf,
> >          */
> >         do {
> >                 struct i2c_msg msgs[] = {
> > -                       {
> > +                       { /*set segment pointer */
> > +                               .addr   = DDC_SEGMENT_ADDR,
> > +                               .flags  = segment ? 0 : I2C_M_IGNORE_NAK,
>
> I don't get the idea. If segment == 0, this message is never sent, so the
> value of field flags doesn't matter. So flags will always be 0 when this
> message is sent, so it can be hard-coded.
>
> Agreed.

> But from previous discussions my understanding was an agreement on always
> using I2C_M_IGNORE_NAK for improved compatibility. So I2C_M_IGNORE_NAK
> should be hard-coded, not 0?
>
After discussion,daniel had asked for a seprate patch for the flags
modification.
Will upload that later.

>
>
> +                               .len    = 1,
> > +                               .buf    = &segment,
> > +                       }, {
> >                                 .addr   = DDC_ADDR,
> >                                 .flags  = 0,
> >                                 .len    = 1,
> > @@ -276,15 +283,22 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter,
> > unsigned char *buf,
> >                                 .buf    = buf,
> >                         }
> >                 };
> > -               ret = i2c_transfer(adapter, msgs, 2);
> > +       /* Avoid sending the segment addr to not upset non-compliant ddc
> > +        * monitors.
> > +        */
>
> s/segment addr/segment/, plus it's abot E-DCC compliance as I understand
> it,
> not DDC.
>
> > +               if (!segment)
> > +                       ret = i2c_transfer(adapter, &msgs[1], xfers);
> > +               else
> > +                       ret = i2c_transfer(adapter, msgs, xfers);
> > +
>
> This can be written:
>
>                 ret = i2c_transfer(adapter, &msgs[3 - xfers], xfers);
>
> Which is more compact and, I suspect, faster.
>
> Agreed.

> >                 if (ret == -ENXIO) {
> >                         DRM_DEBUG_KMS("drm: skipping non-existent
> adapter %s\n",
> >                                         adapter->name);
> >                         break;
> >                 }
> > -       } while (ret != 2 && --retries);
> > +       } while (ret != xfers && --retries);
> >
> > -       return ret == 2 ? 0 : -1;
> > +       return ret == xfers ? 0 : -1;
> >  }
> >
> >  static bool drm_edid_is_zero(u8 *in_edid, int length)
>
> Other than this, your code looks reasonable, not so different from what
> I submitted 8 months ago actually. But ISTU you can test the code with
> real hardware while I couldn't.
>
> Your patch never checked for the 3 message transfer complete, it checked
only 2.

With the changes above applied, you can add:
>
> Reviewed-by: Jean Delvare <jdelvare@suse.de>
>
> Will add your review comments in patch set 5 and your reviewed tag.

Thanks & Regards,
Shirish S

> --
> Jean Delvare
> Suse L3
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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