Re: [PATCH] arm64: dts: rockchip: Fix rk3399-gru-* s2r (pinctrl hogs, wifi reset)

[Enric Balletbo i Serra <enric.balletbo@collabora.com>]

Hi Doug,

On 27/02/18 21:47, Douglas Anderson wrote:
> Back in the early days when gru devices were still under development
> we found an issue where the WiFi reset line needed to be configured as
> early as possible during the boot process to avoid the WiFi module
> being in a bad state.
> 
> We found that the way to get the kernel to do this in the earliest
> possible place was to configure this line in the pinctrl hogs, so
> that's what we did.  For some history here you can see
> <http://crosreview.com/368770>.  After the time that change landed in
> the kernel, we landed a firmware change to configure this line even
> earlier.  See <http://crosreview.com/399919>.  However, even after the
> firmware change landed we kept the kernel change to deal with the fact
> that some people working on devices might take a little while to
> update their firmware.
> 
> At this there are definitely zero devices out in the wild that have
> firmware without the fix in it.  Specifically looking in the firmware
> branch several critically important fixes for memory stability landed
> after the patch in coreboot and I know we didn't ship without those.
> Thus, by now, everyone should have the new firmware and it's safe to
> not have the kernel set this up in a pinctrl hog.
> 
> Historically, even though it wasn't needed to have this in a pinctrl
> hog, we still kept it since it didn't hurt.  Pinctrl would apply the
> default hog at bootup and then would never touch things again.  That
> all changed with commit 981ed1bfbc6c ("pinctrl: Really force states
> during suspend/resume").  After that commit then we'll re-apply the
> default hog at resume time and that can screw up the reset state of
> WiFi.  ...and on rk3399 if you touch a device on PCIe in the wrong way
> then the whole system can go haywire.  That's what was happening.
> Specifically you'd resume a rk3399-gru-* device and it would mostly
> resume, then would crash with some crazy weird crash.
> 
> One could say, perhaps, that the recent pinctrl change was at fault
> (and should be fixed) since it changed behavior.  ...but that's not
> really true.  The device tree for rk3399-gru is really to blame.
> Specifically since the pinctrl is defined in the hog and not in the
> "wlan-pd-n" node then the actual user of this pin doesn't have a
> pinctrl entry for it.  That's bad.
> 
> Let's fix our problems by just moving the control of
> "wlan_module_reset_l pinctrl" out of the hog and put them in the
> proper place.
> 
> NOTE: in theory, I think it should actually be possible to have a pin
> controlled _both_ by the hog and by an actual device.  Once the device
> claims the pin I think the hog is supposed to let go.  I'm not 100%
> sure that this works and in any case this solution would be more
> complex than is necessary.
> 
> Reported-by: Marc Zyngier <marc.zyngier@arm.com>
> Fixes: 48f4d9796d99 ("arm64: dts: rockchip: add Gru/Kevin DTS")
> Fixes: 981ed1bfbc6c ("pinctrl: Really force states during suspend/resume")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
>  arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> index 6e50768a34ce..9ad54751d0d8 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399-gru.dtsi
> @@ -406,8 +406,9 @@
>  	wlan_pd_n: wlan-pd-n {
>  		compatible = "regulator-fixed";
>  		regulator-name = "wlan_pd_n";
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&wlan_module_reset_l>;
>  
> -		/* Note the wlan_module_reset_l pinctrl */
>  		enable-active-high;
>  		gpio = <&gpio1 11 GPIO_ACTIVE_HIGH>;
>  
> @@ -988,12 +989,6 @@ ap_i2c_audio: &i2c8 {
>  	pinctrl-0 = <
>  		&ap_pwroff	/* AP will auto-assert this when in S3 */
>  		&clk_32k	/* This pin is always 32k on gru boards */
> -
> -		/*
> -		 * We want this driven low ASAP; firmware should help us, but
> -		 * we can help ourselves too.
> -		 */
> -		&wlan_module_reset_l
>  	>;
>  
>  	pcfg_output_low: pcfg-output-low {
> @@ -1173,12 +1168,7 @@ ap_i2c_audio: &i2c8 {
>  		};
>  
>  		wlan_module_reset_l: wlan-module-reset-l {
> -			/*
> -			 * We want this driven low ASAP (As {Soon,Strongly} As
> -			 * Possible), to avoid leakage through the powered-down
> -			 * WiFi.
> -			 */
> -			rockchip,pins = <1 11 RK_FUNC_GPIO &pcfg_output_low>;
> +			rockchip,pins = <1 11 RK_FUNC_GPIO &pcfg_pull_none>;
>  		};
>  
>  		bt_host_wake_l: bt-host-wake-l {
> 

In linux-next there are still different issues with s2r, but definitely, this
patch has allowed me to enable again the PCIE on my Samsung Chromebook Plus, s2r
goes now a bit further :) So many thanks for the patch.

Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Regards,
  Enric