linux-kernel - Re: [PATCH v4 1/2] soc: samsung: exynos-pmu: Add regmap support for SoCs that protect PMU regs

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Date: Fri, 9 Feb 2024 15:19:23 +0000
From: Peter Griffin <peter.griffin@...aro.org>
To: Alexey Klimov <alexey.klimov@...aro.org>
Cc: arnd@...db.de, krzysztof.kozlowski@...aro.org, linux@...ck-us.net, 
	wim@...ux-watchdog.org, alim.akhtar@...sung.com, jaewon02.kim@...sung.com, 
	semen.protsenko@...aro.org, kernel-team@...roid.com, tudor.ambarus@...aro.org, 
	andre.draszik@...aro.org, saravanak@...gle.com, willmcvicker@...gle.com, 
	linux-fsd@...la.com, linux-watchdog@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v4 1/2] soc: samsung: exynos-pmu: Add regmap support for
 SoCs that protect PMU regs

Hi Alexey,

On Fri, 9 Feb 2024 at 14:52, Alexey Klimov <alexey.klimov@...aro.org> wrote:
>
> On Thu, 8 Feb 2024 at 16:21, Peter Griffin <peter.griffin@...aro.org> wrote:
> >
> > Some Exynos based SoCs like Tensor gs101 protect the PMU registers for
> > security hardening reasons so that they are only write accessible in el3
> > via an SMC call.
> >
> > As most Exynos drivers that need to write PMU registers currently obtain a
> > regmap via syscon (phys, pinctrl, watchdog). Support for the above usecase
> > is implemented in this driver using a custom regmap similar to syscon to
> > handle the SMC call. Platforms that don't secure PMU registers, get a mmio
> > regmap like before. As regmaps abstract out the underlying register access
> > changes to the leaf drivers are minimal.
> >
> > A new API exynos_get_pmu_regmap_by_phandle() is provided for leaf drivers
> > that currently use syscon_regmap_lookup_by_phandle(). This also handles
> > deferred probing.
> >
> > Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
>
> Tested-by: Alexey Klimov <alexey.klimov@...aro.org>

Thanks for testing this on odroid xu3 hardware!

>
> Apparently it seems tested-by should be provided for both patches. This was
> also tested on odroid xu3 and I also have WIP code that depends on this
> SMC-based regmap. No issues are observed and behaves as expected.
>
> > ---
> > Changes since v3:
> >  - Fix PMUALIVE_MASK
> >  - Add TENSOR_ prefix
> >  - clear SET_BITS bits on each loop iteration
> >  - change set_bit to set_bits in func name
> >  - Fix some alignment
> >  - Add missing return on dev_err_probe
> >  - Reduce indentation in loop
>
> I no longer see the compilation warning related to struct device_node declared
> inside parameter list with v4, I guess one line change addition in exynos-pmu.h
> does the job.

I added a forward declaration in the header to get rid of that
compiler warning in v4, but it's not explicitly mentioned in the above
changelog.

Thanks,

Peter.


Peter