linux-kernel - Re: [PATCH v2] clk: exynos7: Keep aclk_fsys1

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Date:   Mon, 9 Nov 2020 17:35:29 +0100
From:   Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
To:     Sylwester Nawrocki <snawrocki@...nel.org>
Cc:     kgene@...nel.org, krzk@...nel.org, mturquette@...libre.com,
        sboyd@...nel.org, s.nawrocki@...sung.com, tomasz.figa@...il.com,
        cw00.choi@...sung.com, linux-samsung-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] clk: exynos7: Keep aclk_fsys1_200 enabled



On 09.11.2020 13:32, Sylwester Nawrocki wrote:
> Hi Paweł,
> 
> On 11/7/20 13:14, Paweł Chmiel wrote:
>> This clock must be always enabled to allow access to any registers in
>> fsys1 CMU. Until proper solution based on runtime PM is applied
>> (similar to what was done for Exynos5433), fix this by calling
>> clk_prepare_enable() directly from clock provider driver.
>>
>> It was observed on Samsung Galaxy S6 device (based on Exynos7420), where
>> UFS module is probed before pmic used to power that device.
>> In this case defer probe was happening and that clock was disabled by
>> UFS driver, causing whole boot to hang on next CMU access.
>>
>> Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
> 
>> --- a/drivers/clk/samsung/clk-exynos7.c
>> +++ b/drivers/clk/samsung/clk-exynos7.c
> 
>> @@ -571,6 +572,10 @@ static const struct samsung_cmu_info top1_cmu_info __initconst = {
>>   static void __init exynos7_clk_top1_init(struct device_node *np)
>>   {
>>   	samsung_cmu_register_one(np, &top1_cmu_info);
>> +	/*
>> +	 * Keep top FSYS1 aclk enabled permanently. It's required for CMU register access.
>> +	 */
>> +	clk_prepare_enable(__clk_lookup("aclk_fsys1_200"));
> 
> Thanks for the patch. Could you rework it to avoid the __clk_lookup() call?
> I.e. could you change it to something along the lines of:
Hi.
I'll send v3 version with this fixed.

Thanks for review and comments
> 
> -------------8<----------------
> diff --git a/drivers/clk/samsung/clk-exynos7.c b/drivers/clk/samsung/clk-exynos7.c
> index 87ee1ba..9ecf498 100644
> --- a/drivers/clk/samsung/clk-exynos7.c
> +++ b/drivers/clk/samsung/clk-exynos7.c
> @@ -570,7 +570,15 @@ static const struct samsung_cmu_info top1_cmu_info __initconst = {
>  
>  static void __init exynos7_clk_top1_init(struct device_node *np)
>  {
> -       samsung_cmu_register_one(np, &top1_cmu_info);
> +       struct samsung_clk_provider *ctx;
> +       struct clk_hw **hws;
> +
> +       ctx = samsung_cmu_register_one(np, &top1_cmu_info);
> +       if (!ctx)
> +               return;
> +       hws = ctx->clk_data.hws;
> +
> +       clk_prepare_enable(hws[CLK_ACLK_FSYS1_200]);
>  }
>  
>  CLK_OF_DECLARE(exynos7_clk_top1, "samsung,exynos7-clock-top1",
> -------------8<----------------
> ?
> 
> --
> Regards,
> Sylwester
> 
>