linux-kernel - Re: [PATCH v1 2/2] ARM: dts: samsung: Add cache information to the Exynos542x SoC

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Message-ID: <CANAwSgSbSgXwOQLrVrHD7jpDe0=Bq7r2K8p0JjvZJMPpVNq4XQ@mail.gmail.com>
Date: Tue, 30 Jul 2024 18:50:27 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] ARM: dts: samsung: Add cache information to the
 Exynos542x SoC

Hi Krzysztof,

On Tue, 30 Jul 2024 at 17:57, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 30/07/2024 14:06, Anand Moon wrote:
> > Hi Marek,
> >
> > On Tue, 30 Jul 2024 at 17:14, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
> >>
> >>
> >> On 30.07.2024 11:13, Anand Moon wrote:
> >>> As per Exynos 5422 user manual add missing cache information to
> >>> the Exynos542x SoC.
> >>>
> >>> - Each Cortex-A7 core has 32 KB of instruction cache and
> >>>       32 KB of L1 data cache available.
> >>> - Each Cortex-A15 core has 32 KB of L1 instruction cache and
> >>>       32 KB of L1 data cache available.
> >>> - The little (A7) cluster has 512 KB of unified L2 cache available.
> >>> - The big (A15) cluster has 2 MB of unified L2 cache available.
> >>>
> >>> Features:
> >>> - Exynos 5422 support cache coherency interconnect (CCI) bus with
> >>>    L2 cache snooping capability. This hardware automatic L2 cache
> >>>    snooping removes the efforts of synchronizing the contents of the
> >>>    two L2 caches in core switching event.
> >>>
> >>> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> >>
> >>
> >> The provided values are not correct. Please refer to commit 5f41f9198f29
> >> ("ARM: 8864/1: Add workaround for I-Cache line size mismatch between CPU
> >> cores"), which adds workaround for different l1 icache line size between
> >> big and little CPUs. This workaround gets enabled on all Exynos542x/5800
> >> boards.
> >>
> > Ok, I have just referred to the Exynos 5422 user manual for this patch,
> > This patch is just updating the cache size for CPU for big.litle architecture..
> >
>
> Let me get it right. Marek's comment was that you used wrong values.
> Marek also provided rationale for this. Now your reply is that you
> update cache size? Sorry, I fail how you address Marek's comment.
>
> Do not repeat what the patch is doing. We all can see it. Instead
> respond to the comment with some sort of arguments.
>

Ok, If I am not wrong  icache_size is hard-coded in the above commit.

+#ifdef CONFIG_CPU_ICACHE_MISMATCH_WORKAROUND
+.globl icache_size
+       .data
+       .align  2
+icache_size:
+       .long   64
+       .text
+#endif

In the check_cpu_icache_size function, we read the control reg
and recalculate the icache_size.
if there mismatch we re-apply the Icache_size,

So dts passed values do not apply over here,

> Best regards,
> Krzysztof
>

Thanks
-Anand