linux-kernel - Re: [PATCH v3] clk: samsung: Prevent potential endless loop in the PLL set

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Message-ID: <c3c40d62-f5bb-6b13-0af9-ce774718eaa6@samsung.com>
Date:   Tue, 15 Sep 2020 13:34:24 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>, tomasz.figa@...il.com
Cc:     linux-clk@...r.kernel.org, sboyd@...nel.org,
        mturquette@...libre.com, linux-samsung-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, b.zolnierkie@...sung.com,
        m.szyprowski@...sung.com
Subject: Re: [PATCH v3] clk: samsung: Prevent potential endless loop in the
 PLL set_rate ops

On 14.08.2020 02:46, Chanwoo Choi wrote:
> On 8/13/20 6:55 PM, Sylwester Nawrocki wrote:
>> In the .set_rate callback for some PLLs there is a loop polling state
>> of the PLL lock bit and it may become an endless loop when something
>> goes wrong with the PLL. For some PLLs there is already code for polling
>> with a timeout but it uses the ktime API, which doesn't work in some
>> conditions when the set_rate op is called, in particular during
>> initialization of the clk provider before the clocksource initialization
>> has completed. Hence the ktime API cannot be used to reliably detect
>> the PLL locking timeout.
>>
>> This patch adds a common helper function for busy waiting on the PLL lock
>> bit with timeout detection.

>> Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
>> ---
>> Changes for v3:
>>  - use busy-loop with udelay() instead of ktime API
>> Changes for v2:
>>  - use common readl_relaxed_poll_timeout_atomic() macro
>> ---
>>  drivers/clk/samsung/clk-pll.c | 94 ++++++++++++++++---------------------------
>>  1 file changed, 34 insertions(+), 60 deletions(-)

> Thanks.
> 
> Acked-by: Chanwoo Choi <cw00.choi@...sung.com>
 
Patch applied, thank you for your comments.