linux-kernel - Re: [PATCH 07/13] clk: samsung: gs101: mark PERIC0 IP TOP gate clock as critical

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Message-ID: <CAPLW+4mNjCbJ+VbKR66DFSkiXHyxdjgvwjN7azxjJQ6UxQikEw@mail.gmail.com>
Date:   Thu, 14 Dec 2023 09:37:31 -0600
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Tudor Ambarus <tudor.ambarus@...aro.org>
Cc:     peter.griffin@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
        sboyd@...nel.org, conor+dt@...nel.org, andi.shyti@...nel.org,
        alim.akhtar@...sung.com, gregkh@...uxfoundation.org,
        jirislaby@...nel.org, catalin.marinas@....com, will@...nel.org,
        s.nawrocki@...sung.com, tomasz.figa@...il.com,
        cw00.choi@...sung.com, arnd@...db.de, andre.draszik@...aro.org,
        saravanak@...gle.com, willmcvicker@...gle.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 07/13] clk: samsung: gs101: mark PERIC0 IP TOP gate clock
 as critical

On Thu, Dec 14, 2023 at 4:52 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
> Testing USI8 I2C with an eeprom revealed that when the USI8 leaf clock
> is disabled it leads to the CMU_TOP PERIC0 IP gate clock disablement,
> which then makes the system hang. To prevent this, mark
> CLK_GOUT_CMU_PERIC0_IP as critical. Other clocks will be marked
> accordingly when tested.
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
>  drivers/clk/samsung/clk-gs101.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/samsung/clk-gs101.c b/drivers/clk/samsung/clk-gs101.c
> index 3d194520b05e..08d80fca9cd6 100644
> --- a/drivers/clk/samsung/clk-gs101.c
> +++ b/drivers/clk/samsung/clk-gs101.c
> @@ -1402,7 +1402,7 @@ static const struct samsung_gate_clock cmu_top_gate_clks[] __initconst = {
>              "mout_cmu_peric0_bus", CLK_CON_GAT_GATE_CLKCMU_PERIC0_BUS,
>              21, 0, 0),
>         GATE(CLK_GOUT_CMU_PERIC0_IP, "gout_cmu_peric0_ip", "mout_cmu_peric0_ip",
> -            CLK_CON_GAT_GATE_CLKCMU_PERIC0_IP, 21, 0, 0),
> +            CLK_CON_GAT_GATE_CLKCMU_PERIC0_IP, 21, CLK_IS_CRITICAL, 0),

This clock doesn't seem like a leaf clock. It's also not a bus clock.
Leaving it always running makes the whole PERIC0 CMU clocked, which
usually should be avoided. Is it possible that the system freezes
because some other clock (which depends on peric0_ip) gets disabled as
a consequence of disabling peric0_ip? Maybe it's some leaf clock which
is not implemented yet in the clock driver? Just looks weird to me
that the system hangs because of CMU IP clock disablement. It's
usually something much more specific.

>         GATE(CLK_GOUT_CMU_PERIC1_BUS, "gout_cmu_peric1_bus",
>              "mout_cmu_peric1_bus", CLK_CON_GAT_GATE_CLKCMU_PERIC1_BUS,
>              21, 0, 0),
> --
> 2.43.0.472.g3155946c3a-goog
>