From 748103e7235892bf9a3ee568d7d4dd7e5a3beece Mon Sep 17 00:00:00 2001 From: Stefani Seibold Date: Mon, 3 Jan 2011 09:28:59 +0000 Subject: [PATCH] drivers/video/i810/i810-i2c.c: fix i2c bus handling 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. Signed-off-by: Stefani Seibold Cc: Paul Mundt Cc: Jean Delvare Signed-off-by: Andrew Morton Signed-off-by: Paul Mundt --- drivers/video/i810/i810-i2c.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/video/i810/i810-i2c.c b/drivers/video/i810/i810-i2c.c index cd2c728a809b..7db17d0d8a8c 100644 --- a/drivers/video/i810/i810-i2c.c +++ b/drivers/video/i810/i810-i2c.c @@ -45,8 +45,10 @@ static void i810i2c_setscl(void *data, int state) struct i810fb_par *par = chan->par; u8 __iomem *mmio = par->mmio_start_virtual; - i810_writel(mmio, chan->ddc_base, (state ? SCL_VAL_OUT : 0) | SCL_DIR | - SCL_DIR_MASK | SCL_VAL_MASK); + if (state) + i810_writel(mmio, chan->ddc_base, SCL_DIR_MASK | SCL_VAL_MASK); + else + i810_writel(mmio, chan->ddc_base, SCL_DIR | SCL_DIR_MASK | SCL_VAL_MASK); i810_readl(mmio, chan->ddc_base); /* flush posted write */ } @@ -56,8 +58,10 @@ static void i810i2c_setsda(void *data, int state) struct i810fb_par *par = chan->par; u8 __iomem *mmio = par->mmio_start_virtual; - i810_writel(mmio, chan->ddc_base, (state ? SDA_VAL_OUT : 0) | SDA_DIR | - SDA_DIR_MASK | SDA_VAL_MASK); + if (state) + i810_writel(mmio, chan->ddc_base, SDA_DIR_MASK | SDA_VAL_MASK); + else + i810_writel(mmio, chan->ddc_base, SDA_DIR | SDA_DIR_MASK | SDA_VAL_MASK); i810_readl(mmio, chan->ddc_base); /* flush posted write */ } -- 2.20.1