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

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Date:   Thu, 14 Dec 2023 16:01:18 +0000
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     Sam Protsenko <semen.protsenko@...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 12/14/23 15:37, Sam Protsenko wrote:
> 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.

The system hang happened when I tested USI8 in I2C configuration with an
eeprom. After the eeprom is read the leaf gate clock that gets disabled
is the one on PERIC0 (CLK_GOUT_PERIC0_CLK_PERIC0_USI8_USI_CLK). I assume
this leads to the CMU_TOP gate (CLK_CON_GAT_GATE_CLKCMU_PERIC0_IP)
disablement which makes the system hang. Either marking the CMU_TOP gate
clock as critical (as I did in this patch) or marking the leaf PERIC0
gate clock as critical, gets rid of the system hang. Did I choose wrong?

Thanks,
ta
> 
>>         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
>>