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

[Marc Zyngier]

On 27/02/18 20:47, 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@xxxxxxx>
> Fixes: 48f4d9796d99 ("arm64: dts: rockchip: add Gru/Kevin DTS")
> Fixes: 981ed1bfbc6c ("pinctrl: Really force states during suspend/resume")
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>

Tested-by: Marc Zyngier <marc.zyngier@xxxxxxx>

Thanks,

	M.
-- 
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