linux-kernel - Re: [PATCH] fix i810 i2c bug

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Date:	Thu, 6 Jan 2011 15:53:29 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	linux-fbdev@...r.kernel.org, adaplas@...il.com,
	Maik Broemme <mbroemme@...sserver.de>,
	Dave Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] fix i810 i2c bug

On Mon, Jan 03, 2011 at 10:28:59AM +0100, Stefani Seibold wrote:
> These patch fix a longstanding bug in the i810 frame buffer driver. 
> 
> The handling of the i2c bus is wrong: A 1 bit should not written to the
> i2c, these will be done by switch the i2c to input. Driving an 1 bit
> active is against the i2c spec.
> 
> An active driven of a 1 bit will result in very strange error, depending
> which side is the more powerful one. In my case it depends on the
> temperature of the Display-Controller-EEprom: With an cold eprom a got
> the correct EDID datas, with a warm one some of the 1 bits was 0 :-(
> 
> The same bug is also in the intelfb driver in the file
> drivers/video/intelfb/intelfb_i2c.c. The functions intelfb_gpio_setscl()
> and intelfb_gpio_setsda() do drive the 1 bit active to the i2c bus. But
> since i have no card which is used by the intelfb driver i cannot fix
> it.
> 
> The patch is against linux next-20101231
> 
> - Stefani
> 
> Signed-off-by: Stefani Seibold <stefani@...bold.net>

Applied, thanks.

Also adding intelfb people to the Cc so they're aware of the problem, and
can follow suit.
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