[PATCH v2] drm/i915: Run DDC buses at 50 kbps

[Daniel Vetter]

On Wed, Mar 21, 2012 at 02:29:47PM +0100, Jean Delvare wrote:
> A udelay value of 20 leads to an I2C bus running at only 25 kbps. I2C
> devices can typically operate faster than this, 50 kbps should be fine
> for all devices (and compliant devices can always stretch the clock if
> needed.)
> 
> FWIW, the vast majority of framebuffer drivers set udelay to 10
> already. So set it to 10 in DRM drivers too, this will make EDID block
> reads faster. We might even lower the udelay value later if no problem
> is reported.
> 
> Signed-off-by: Jean Delvare <jdelvare at suse.de>
> Acked-by: Eugeni Dodonov <eugeni.dodonov at intel.com>
> Cc: Dave Airlie <airlied at gmail.com>
> Cc: Keith Packard <keithp at keithp.com>

Fyi this already got merged int Dave's tree (the unsplit version) as:

commit 1849ecb22fb3b5d57b65e7369a3957adf9f26f39
Author: Jean Delvare <jdelvare at suse.de>
Date:   Sat Jan 28 11:07:09 2012 +0100

    drm/kms: Make i2c buses faster

Cheers, Daniel

> ---
> Changes since v1:
> * Split per driver to make merging easier.
> * Make the subject line more accurate.
> 
>  drivers/gpu/drm/i915/intel_i2c.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- linux-3.4-rc0.orig/drivers/gpu/drm/i915/intel_i2c.c	2012-03-21 13:43:33.750915151 +0100
> +++ linux-3.4-rc0/drivers/gpu/drm/i915/intel_i2c.c	2012-03-21 13:44:05.923915628 +0100
> @@ -37,7 +37,7 @@
>  
>  /* Intel GPIO access functions */
>  
> -#define I2C_RISEFALL_TIME 20
> +#define I2C_RISEFALL_TIME 10
>  
>  static inline struct intel_gmbus *
>  to_intel_gmbus(struct i2c_adapter *i2c)
> 
> -- 
> Jean Delvare
> Suse L3
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> http://lists.freedesktop.org/mailman/listinfo/dri-devel

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