linux-kernel - Re: [PATCH v2 7/9] clk: samsung: exynos850: Implement CMU

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Message-ID: <af463efe-1656-5638-b41a-5daea3099812@linaro.org>
Date:   Fri, 12 Aug 2022 12:55:15 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Chanho Park <chanho61.park@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Tomasz Figa <tomasz.figa@...il.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v2 7/9] clk: samsung: exynos850: Implement CMU_MFCMSCL
 domain

On 09/08/2022 14:33, Sam Protsenko wrote:
> CMU_MFCMSCL clock domain provides clocks for MFC (Multi-Format Codec),
> JPEG Codec and Scaler IP-cores. According to Exynos850 TRM, CMU_MFCMSCL
> generates MFC, M2M, MCSC and JPEG clocks for BLK_MFCMSCL.
> 
> This patch adds next clocks:
>   - bus clocks in CMU_TOP for CMU_MFCMSCL
>   - all internal CMU_MFCMSCL clocks
>   - leaf clocks for MFCMSCL, TZPC (TrustZone Protection Controller),
>     JPEG codec, M2M (Memory-to-Memory), MCSC (Multi-Channel Scaler),
>     MFC (Multi-Format Codec), PPMU (Platform Performance Monitoring
>     Unit), SysMMU and SysReg
> 
> MFCMSCL related gate clocks in CMU_TOP were marked as CLK_IS_CRITICAL,
> because:
>   1. All of those have to be enabled in order to read
>      /sys/kernel/debug/clk/clk_summary file
>   2. When some user driver (e.g. exynos-sysmmu) disables some derived
>      leaf clock, it can lead to CMU_TOP clocks disable, which then makes
>      the system hang. To prevent that, the CLK_IS_CRITICAL flag is used,
>      as CLK_IGNORE_UNUSED is not enough.

No, same as with ISP these are not critical clocks.

Best regards,
Krzysztof