linux-kernel - Re: [PATCH] clk: samsung: fsd: Mark PLL_CAM

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Message-ID: <633ff284-101d-4651-833e-a6b01626c9a1@kernel.org>
Date: Thu, 19 Sep 2024 14:03:08 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Inbaraj E <inbaraj.e@...sung.com>, 'Stephen Boyd' <sboyd@...nel.org>,
 alim.akhtar@...sung.com, cw00.choi@...sung.com, linux-clk@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
 mturquette@...libre.com, s.nawrocki@...sung.com
Cc: pankaj.dubey@...sung.com, gost.dev@...sung.com
Subject: Re: [PATCH] clk: samsung: fsd: Mark PLL_CAM_CSI as critical

On 19/09/2024 13:33, Inbaraj E wrote:
> 
> 
>> -----Original Message-----
>> From: Stephen Boyd <sboyd@...nel.org>
>> Sent: 19 September 2024 15:51
>> To: Inbaraj E <inbaraj.e@...sung.com>; alim.akhtar@...sung.com;
>> cw00.choi@...sung.com; krzk@...nel.org; linux-clk@...r.kernel.org; linux-
>> kernel@...r.kernel.org; linux-samsung-soc@...r.kernel.org;
>> mturquette@...libre.com; s.nawrocki@...sung.com
>> Cc: pankaj.dubey@...sung.com; gost.dev@...sung.com; Inbaraj E
>> <inbaraj.e@...sung.com>
>> Subject: Re: [PATCH] clk: samsung: fsd: Mark PLL_CAM_CSI as critical
>>
>> Quoting Inbaraj E (2024-09-17 03:10:16)
>>> PLL_CAM_CSI is the parent clock for the ACLK and PCLK in the
>>> CMU_CAM_CSI block. When we gate ACLK or PCLK, the clock framework
>> will
>>> subsequently disables the parent clocks(PLL_CAM_CSI). Disabling
>>> PLL_CAM_CSI is causing sytem level halt.
>>>
>>> It was observed on FSD SoC, when we gate the ACLK and PCLK during CSI
>>> stop streaming through pm_runtime_put system is getting halted. So
>>> marking PLL_CAM_CSI as critical to prevent disabling.
>>>
>>> Signed-off-by: Inbaraj E <inbaraj.e@...sung.com>
>>> ---
>>
>> Please add a fixes tag. Although this is likely a band-aid fix because marking
>> something critical leaves it enabled forever.
> 
> Sure, will add fixes tag. As per HW manual, this PLL_CAM_CSI is
> supplying clock even for CMU SFR access of CSI block, so we can't
> gate this.

Hm, I am not so sure. The CMU driver should just take appropriate clock.
Sprinkling CLK_CRITICAL looks as substitute of missing clock handling/


Best regards,
Krzysztof