linux-kernel - Re: [PATCH v2] clk: tegra: Use readl_relaxed_poll_timeout_atomic in tegra210_clock

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Message-ID: <731a934a-4e78-b96d-239f-14cf83079605@nvidia.com>
Date:   Fri, 20 Oct 2017 11:20:24 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>,
        Thierry Reding <thierry.reding@...il.com>
CC:     <sboyd@...eaurora.org>, <pdeschrijver@...dia.com>,
        <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <mturquette@...libre.com>,
        <pgaikwad@...dia.com>
Subject: Re: [PATCH v2] clk: tegra: Use readl_relaxed_poll_timeout_atomic in
 tegra210_clock_init


On 19/10/17 19:42, Nicolin Chen wrote:
> On Thu, Oct 19, 2017 at 11:44:22AM +0200, Thierry Reding wrote:
>>>> Below is the call trace of tegra210_init_pllu() function:
>>>>   start_kernel()
>>>>   -> time_init()
>>>>   --> of_clk_init()
>>>>   ---> tegra210_clock_init()
>>>>   ----> tegra210_pll_init()
>>>>   -----> tegra210_init_pllu()
> 
>> I'm wondering why we're not seeing a splat for this. Usually the kernel
>> will warn if you sleep during atomic context. Does this mean we're just
>> not hitting that case?
> 
> Yes.
> 
>> readx_poll_timeout() has a might_sleep_if(), and
>> therefore it should always cause the splat.
> 
> That's true as long as CONFIG_DEBUG_ATOMIC_SLEEP is enabled locally.
> 
>> Any ideas why this has gone unnoticed for all this time?
> 
> We can see in the tegra210_init_pllu() function that it'll not call
> tegra210_enable_pllu() if pllu is already enabled (by bootloader).

I was thinking that same and so I clobbered the PLLU enable bit with
u-boot, however, then the kernel appears to hang on boot when enabling
the PLL. So although this is probably a separate issue, I am curious if
you have booted the mainline with the PLLU disabled?

Cheers
Jon

-- 
nvpublic