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

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Date:   Mon, 9 Nov 2020 13:32:09 +0100
From:   Sylwester Nawrocki <snawrocki@...nel.org>
To:     Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>
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

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:

-------------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