On Mon, Jul 25, 2022 at 4:39 PM AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote: > > Il 25/07/22 10:24, Pin-yen Lin ha scritto: > > Switch to SMC watchdog because we need direct control of HW watchdog > > registers from kernel. The corresponding firmware was uploaded in > > https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405. > > > > There's a fundamental issue with this change, I think. > > What happens if we run this devicetree on a device that does *not* have > the new(er) firmware? I haven't tried this patch with an older firmware. I'll manage to build one for this. > > The kernel *shall not* get broken when running on devices that are running > on older firmware, especially because that's what was initially supported > and what is working right now. Actually the current approach does not work *right*. The device boots, but the watchdog does not work properly. Also, all MT8173 ChromeOS devices have this firmware updated, and we don't have other upstream users apart from mt8173-evb. Do we want to support the developers that are running upstream linux with their MT8173 boards? > > For this reason, I think that we should get some code around that checks > if the SMC watchdog is supported and, if not, resort to MMIO wdog. What is the expected way to support this backward compatibility? Do we put the old compatible strings ("mediatek,mt8173-wdt" and "mediatek,mt6589-wdt") after "arm,smc-wdt" and reject it in the drivers if the firmware does not support it? > > Regards, > Angelo > > > > Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx> > > --- > > > > arch/arm64/boot/dts/mediatek/mt8173.dtsi | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/arch/arm64/boot/dts/mediatek/mt8173.dtsi b/arch/arm64/boot/dts/mediatek/mt8173.dtsi > > index a2aef5aa67c1..2d1c776740a5 100644 > > --- a/arch/arm64/boot/dts/mediatek/mt8173.dtsi > > +++ b/arch/arm64/boot/dts/mediatek/mt8173.dtsi > > @@ -528,10 +528,8 @@ power-domain@MT8173_POWER_DOMAIN_MFG { > > }; > > }; > > > > - watchdog: watchdog@10007000 { > > - compatible = "mediatek,mt8173-wdt", > > - "mediatek,mt6589-wdt"; > > - reg = <0 0x10007000 0 0x100>; > > + watchdog { > > + compatible = "arm,smc-wdt"; > > }; > > > > timer: timer@10008000 { > > > >
