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

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Message-ID: <a09b6b493b41bff39000df61dd14693af8b0f053.camel@linaro.org>
Date: Mon, 06 Oct 2025 07:36:43 +0100
From: André Draszik <andre.draszik@...aro.org>
To: Sam Protsenko <semen.protsenko@...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 Sam,

On Fri, 2025-10-03 at 11:59 -0500, Sam Protsenko wrote:
> 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?

Yes, but for the system controller (PMU) only.

On E850, it appears to be the same and there are many holes in the PMU memory
range. You can confirm using debugfs by manually skipping invalid ones, e.g.

dd if=/sys/kernel/debug/regmap/dummy-system-controller@...000000011860000/registers \
   ibs=15 count=1 \
   skip=$(( 0x28 / 4 ))

should give you register 0x28 without SError.

while

dd if=/sys/kernel/debug/regmap/dummy-system-controller@...000000011860000/registers \
   ibs=15 count=1 \
   skip=$(( 0x4 / 4 ))

should crash.

>  If so, I'd probably want to adapt it for Exynos850
> later.

+1. Note though that a custom regmap is used on gs101 for the PMU in the first place.


Cheers,
Andre'


>