On Thu, May 18, 2017 at 11:23 AM, Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > To set the mux mode of a pin two bits must be set. Up to now this is > implemented using the following idiom: > > writel(mask, reg + CLR); > writel(value, reg + SET); > > . This however results in the mux mode being 0 between the two writes. > > On my machine there is an IC's reset pin connected to LCD_D20. The > bootloader configures this pin as GPIO output-high (i.e. not holding the > IC in reset). When Linux reconfigures the pin to GPIO the short time > LCD_D20 is muxed as LCD_D20 instead of GPIO_1_20 is enough to confuse > the connected IC. > > The same problem is present for the pin's drive strength setting which is > reset to low drive strength before using the right value. > > So instead of relying on the hardware to modify the register setting > using two writes implement the bit toggling using read-modify-write. > > Fixes: 17723111e64f ("pinctrl: add pinctrl-mxs support") > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> Patch applied for fixes with Shawn's ACK. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html