linux-kernel - Re: [PATCH 0/3] soc: samsung: exynos-pmu: gs101: avoid SError for inaccessible registers

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Message-ID: <CAPLW+4kAzXmd7mv279wMJCT0gVP5A+2Xe0q3MgX1OENH5PC2dQ@mail.gmail.com>
Date: Fri, 3 Oct 2025 11:59:12 -0500
From: Sam Protsenko <semen.protsenko@...aro.org>
To: André Draszik <andre.draszik@...aro.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>, 
	Peter Griffin <peter.griffin@...aro.org>, Tudor Ambarus <tudor.ambarus@...aro.org>, 
	Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] soc: samsung: exynos-pmu: gs101: avoid SError for
 inaccessible registers

Hi Andre,

On Thu, Oct 2, 2025 at 5:33 AM André Draszik <andre.draszik@...aro.org> wrote:
>
> Accessing non-existent PMU registers causes an SError, halting the
> system and rendering it unuseable.
>

I wonder if this issue you describe here is similar to what I'm seeing
on E850-96. When I'm trying to read these files

    /sys/kernel/debug/regmap/dummy-syscon@...000000010020000/registers
    /sys/kernel/debug/regmap/dummy-chipid@...000000010000000/registers
    /sys/kernel/debug/regmap/dummy-system-controller@...000000011860000/registers

I'm seeing "synchronous external abort" during regmap operations
(judging from the backtrace). Do you think this series fixes the same
issue on gs101? If so, I'd probably want to adapt it for Exynos850
later.

> For gs101, we can avoid that by creating the underlying PMU regmap with
> the read- and writable register ranges in place, because on gs101 this
> driver controls creation of the regmap.
>
> This series updates the Exynos PMU driver and gs101 in particular to do
> just that. For gs101 this is easy, as the exynos-pmu driver creates a
> regmap and we can update the regmap config to pass in the registers.
> For other SoCs it's not as straight forward, as syscon_node_to_regmap()
> is used which doesn't allow passing a custom regmap config - those SoCs
> are out of scope for this series.
>
> With this in place, invalid registers (by drivers, or even plain
> debugfs), are now simply skipped by regmap, leaving the system useable
> in that case.
>
> Cheers,
> Andre'
>
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
> ---
> André Draszik (3):
>       soc: samsung: exynos-pmu: allow specifying read & write access tables for secure regmap
>       soc: samsung: exynos-pmu: move some gs101 related code into new file
>       soc: samsung: gs101-pmu: implement access tables for read and write
>
>  MAINTAINERS                                 |   1 +
>  drivers/soc/samsung/Makefile                |   3 +-
>  drivers/soc/samsung/exynos-pmu.c            | 136 +--------
>  drivers/soc/samsung/exynos-pmu.h            |  11 +
>  drivers/soc/samsung/gs101-pmu.c             | 445 ++++++++++++++++++++++++++++
>  include/linux/soc/samsung/exynos-regs-pmu.h | 343 ++++++++++++++++++++-
>  6 files changed, 797 insertions(+), 142 deletions(-)
> ---
> base-commit: 5eb97efbe6a375944984e7fb69bb632d2879c841
> change-id: 20251001-gs101-pmu-regmap-tables-8726ac9f853e
>
> Best regards,
> --
> André Draszik <andre.draszik@...aro.org>
>
>