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@xxxxxxx> Acked-by: Eugeni Dodonov <eugeni.dodonov@xxxxxxxxx> Cc: Dave Airlie <airlied@xxxxxxxxx> Cc: Keith Packard <keithp@xxxxxxxxxx> Cc: Alex Deucher <alexdeucher@xxxxxxxxx> --- Already sent on: 2011-10-21. drivers/gpu/drm/i915/intel_i2c.c | 2 +- drivers/gpu/drm/radeon/radeon_i2c.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- linux-3.3-rc1.orig/drivers/gpu/drm/i915/intel_i2c.c 2012-01-28 10:12:16.554480007 +0100 +++ linux-3.3-rc1/drivers/gpu/drm/i915/intel_i2c.c 2012-01-28 10:28:16.884668894 +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) --- linux-3.3-rc1.orig/drivers/gpu/drm/radeon/radeon_i2c.c 2012-01-28 10:12:16.555480007 +0100 +++ linux-3.3-rc1/drivers/gpu/drm/radeon/radeon_i2c.c 2012-01-28 10:28:16.886668894 +0100 @@ -924,7 +924,7 @@ struct radeon_i2c_chan *radeon_i2c_creat i2c->algo.bit.setscl = set_clock; i2c->algo.bit.getsda = get_data; i2c->algo.bit.getscl = get_clock; - i2c->algo.bit.udelay = 20; + i2c->algo.bit.udelay = 10; /* vesa says 2.2 ms is enough, 1 jiffy doesn't seem to always * make this, 2 jiffies is a lot more reliable */ i2c->algo.bit.timeout = 2; -- Jean Delvare Suse L3 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
