linux-kernel - Re: [PATCH] soc: ti: pm33xx: Enable DS0 for the platforms on which it is functional

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Message-ID: <20180822084318.GN14967@localhost>
Date:   Wed, 22 Aug 2018 10:43:18 +0200
From:   Johan Hovold <johan@...nel.org>
To:     "J, KEERTHY" <j-keerthy@...com>
Cc:     Johan Hovold <johan@...nel.org>, tony@...mide.com,
        d-gerlach@...com, linux-kernel@...r.kernel.org, t-kristo@...com,
        ssantosh@...nel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] soc: ti: pm33xx: Enable DS0 for the platforms on which
 it is functional

On Wed, Aug 22, 2018 at 01:50:29PM +0530, J, KEERTHY wrote:
> 
> 
> On 8/22/2018 1:07 PM, Johan Hovold wrote:
> > On Wed, Aug 22, 2018 at 09:34:09AM +0200, Johan Hovold wrote:
> >> On Wed, Aug 22, 2018 at 11:02:31AM +0530, Keerthy wrote:
> >>> Enable DS0 for only those platforms on which it is functional
> >>>
> >>> Signed-off-by: Keerthy <j-keerthy@...com>
> >>> ---
> >>>   arch/arm/mach-omap2/pm33xx-core.c    | 5 +++++
> >>>   drivers/soc/ti/pm33xx.c              | 9 +++++++++
> >>>   include/linux/platform_data/pm33xx.h | 2 ++
> >>>   3 files changed, 16 insertions(+)
> >>>
> >>> diff --git a/arch/arm/mach-omap2/pm33xx-core.c b/arch/arm/mach-omap2/pm33xx-core.c
> >>> index f4971e4..f0f6e8e 100644
> >>> --- a/arch/arm/mach-omap2/pm33xx-core.c
> >>> +++ b/arch/arm/mach-omap2/pm33xx-core.c
> >>> @@ -135,6 +135,11 @@ static int am43xx_suspend(unsigned int state, int (*fn)(unsigned long),
> >>>   {
> >>>   	int ret = 0;
> >>>   
> >>> +	if (!(args & WFI_FLAG_DEEP_SLEEP0)) {
> >>> +		pr_err("DS0 mode not supported\n");
> >>> +		return -ENOTSUPP;
> >>> +	}
> >>> +
> >>>   	amx3_pre_suspend_common();
> >>>   	scu_power_mode(scu_base, SCU_PM_POWEROFF);
> >>>   	ret = cpu_suspend(args, fn);
> >>> diff --git a/drivers/soc/ti/pm33xx.c b/drivers/soc/ti/pm33xx.c
> >>> index d0dab32..53238d7 100644
> >>> --- a/drivers/soc/ti/pm33xx.c
> >>> +++ b/drivers/soc/ti/pm33xx.c
> >>> @@ -324,6 +324,15 @@ static int am33xx_pm_probe(struct platform_device *pdev)
> >>>   	suspend_wfi_flags |= WFI_FLAG_SAVE_EMIF;
> >>>   	suspend_wfi_flags |= WFI_FLAG_WAKE_M3;
> >>>   
> >>> +	/*
> >>> +	 * Deep Sleep0 mode is currently functional only on am437x-gp-evm,
> >>> +	 * am33xx-evm and boneblack family. Hence set the DS0 flag
> >>> +	 */
> >>> +	if (of_machine_is_compatible("ti,am437x-gp-evm") ||
> >>> +	    of_machine_is_compatible("ti,am335x-bone-black") ||
> >>> +	    of_machine_is_compatible("ti,am335x-evm"))
> >>> +		suspend_wfi_flags |= WFI_FLAG_DEEP_SLEEP0;
> >>
> >> What about other (out-of-tree) machines which supports DS0 and which
> >> this change would break?
> >>
> >> I think this needs to be a blacklist if anything.
> >>
> >> Please also expand in the commit message why you think this is needed.
> 
> Currently when one does echo mem > /sys/power/state on unsuppored 
> machines there can be a crash or a hang. So bail out with a message.

Yes, but why is this unsupported on some machines? Which machines, and
why? Your commit messages should be self-contained and hold the
information needed to determine whether your patch makes sense in the
first place.

> >> Last, what tree is this against? There's no am43xx_suspend() in
> >> linux-next (and you add compatibles above for am33xx too).
> > 
> > Sorry, there is indeed an am43xx_suspend(), but you are adding
> > compatibles for am33xx which use am33xx_suspend().
> 
> am33xx_pm_probe is a common probe function for both am33 and am43.

Yes, but you add a check for your new flag only to am43xx_suspend(), not
to am33xx_suspend() which is used by the am33xx compatibles you add.

> AFAIK for am33 family am335x-evm and am335x-bone-black support Deep 
> Sleep mode. For am43 family am43tx-gp-evm alone supports at the moment.

But these are development boards (EVKs), not SOC families (or
chip revisions). What about all the products that customers to TI who
have bought these SoCs have built?

> Can you let me know of other am33 machines that support DS0 mode?

I have a customer who use DS0, whose DTS is not yet in mainline, and
whose setup this patch would break for example.

> I could have simply used ti,am33xx compatible which covers entire am33 
> family but then am33xx-bone (bone white) does not support this mode.

Yes, and a blacklist would make much more sense for something like this
if where talking about specific boards.

Also note that your patch doesn't even handle bone-white as you didn't
add a check to am33xx_suspend() as I pointed out above.

Johan