Hi Geert,
Thank you for the patch.
On Wednesday 24 May 2017 13:43:34 Geert Uytterhoeven wrote:
> Configuration of the lcd0 pinmux group and GPIO hog for the external
> GPIO mux are done using a single device node, causing the "output-high"
> property to be applied to both. This will fail for the pinmux group,
> but doesn't cause any harm, as the failure is ignored silently.
>
> However, after "pinctrl: sh-pfc: propagate errors on group config", the
> failure will become fatal, leading to a broken display:
>
> sh-pfc e6050000.pin-controller: pin_config_group_set op failed for group
> 102 sh-pfc e6050000.pin-controller: Error applying setting, reverse things
> back sh-pfc e6050000.pin-controller: failed to select default state
>
> Split the configuration in two subnodes, and replace the GPIO hog by a
> pull-up pin bias to fix this.
>
> Fixes: ffd2f9a5afb730b9 ("ARM: shmobile: armadillo800eva dts: Add pinctrl
> and gpio-hog for lcdc0") Signed-off-by: Geert Uytterhoeven
> <geert+renesas@xxxxxxxxx>
> ---
> This is a hard dependency for "pinctrl: sh-pfc: propagate errors on
> group config" (https://patchwork.kernel.org/patch/9186713/).
>
> Notes:
> 1. Just keeping the GPIO hog doesn't work, as the sh-pfc driver
> requires each pinctrl (sub)node to have at least one "pins" or
> "groups" property,
> 2. Keeping "output-high" doesn't work, as the sh-pfc driver does not
> implement PIN_CONFIG_OUTPUT.
>
> Should I fix 1 and/or 2 instead?
> ---
> arch/arm/boot/dts/r8a7740-armadillo800eva.dts | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/boot/dts/r8a7740-armadillo800eva.dts
> b/arch/arm/boot/dts/r8a7740-armadillo800eva.dts index
> 44b335b9f035436d..7feedc86f6915654 100644
> --- a/arch/arm/boot/dts/r8a7740-armadillo800eva.dts
> +++ b/arch/arm/boot/dts/r8a7740-armadillo800eva.dts
> @@ -267,13 +267,16 @@
> };
>
> lcd0_pins: lcd0 {
> - groups = "lcd0_data24_0", "lcd0_lclk_1", "lcd0_sync";
> - function = "lcd0";
> + mux {
> + groups = "lcd0_data24_0", "lcd0_lclk_1", "lcd0_sync";
> + function = "lcd0";
> + };
>
> - /* DBGMD/LCDC0/FSIA MUX */
> - gpio-hog;
> - gpios = <176 0>;
> - output-high;
> + gpio {
> + /* DBGMD/LCDC0/FSIA MUX */
> + pins = "PORT176";
> + bias-pull-up;
The signal is pulled low through a 10kΩ resistor, so a pull-up is a bit weak.
You'll end up with an intermediate voltage level that could result in meta-
stability and/or latch-up. I think we need to really drive the output to 1.
> + };
> };
> };
--
Regards,
Laurent Pinchart
