linux-kernel - Re: [PATCH 1/4] clk: imx8mn: A53 core clock no need to be critical

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Message-ID: <20200311064005.GE29269@dragon>
Date:   Wed, 11 Mar 2020 14:40:05 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Anson Huang <Anson.Huang@....com>
Cc:     mturquette@...libre.com, sboyd@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, leonard.crestez@....com,
        abel.vesa@....com, peng.fan@....com, ping.bai@....com,
        fugang.duan@....com, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Linux-imx@....com
Subject: Re: [PATCH 1/4] clk: imx8mn: A53 core clock no need to be critical

On Tue, Feb 25, 2020 at 04:49:11PM +0800, Anson Huang wrote:
> 'A53_CORE' is just a mux and no need to be critical, being critical
> will cause its parent clock always ON which does NOT make sense,

I do not quite understand what problem this patch is trying to fix.  In
the end, all the ancestor clocks of "arm", including "arm_a53_core" will
still be ON, as "arm" has CLK_IS_CRITICAL flag.  What is the difference
you are trying to make here?

Shawn

> to make sure CPU's hardware clock source NOT being disabled during
> clock tree setup, need to move the 'A53_SRC'/'A53_CORE' reparent
> operations to after critical clock 'ARM_CLK' setup finished.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>
> ---
>  drivers/clk/imx/clk-imx8mn.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/clk/imx/clk-imx8mn.c b/drivers/clk/imx/clk-imx8mn.c
> index 83618af..0bc7070 100644
> --- a/drivers/clk/imx/clk-imx8mn.c
> +++ b/drivers/clk/imx/clk-imx8mn.c
> @@ -428,7 +428,7 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
>  	hws[IMX8MN_CLK_GPU_SHADER_DIV] = hws[IMX8MN_CLK_GPU_SHADER];
>  
>  	/* CORE SEL */
> -	hws[IMX8MN_CLK_A53_CORE] = imx_clk_hw_mux2_flags("arm_a53_core", base + 0x9880, 24, 1, imx8mn_a53_core_sels, ARRAY_SIZE(imx8mn_a53_core_sels), CLK_IS_CRITICAL);
> +	hws[IMX8MN_CLK_A53_CORE] = imx_clk_hw_mux2("arm_a53_core", base + 0x9880, 24, 1, imx8mn_a53_core_sels, ARRAY_SIZE(imx8mn_a53_core_sels));
>  
>  	/* BUS */
>  	hws[IMX8MN_CLK_MAIN_AXI] = imx8m_clk_hw_composite_critical("main_axi", imx8mn_main_axi_sels, base + 0x8800);
> @@ -559,15 +559,15 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
>  
>  	hws[IMX8MN_CLK_DRAM_ALT_ROOT] = imx_clk_hw_fixed_factor("dram_alt_root", "dram_alt", 1, 4);
>  
> -	clk_hw_set_parent(hws[IMX8MN_CLK_A53_SRC], hws[IMX8MN_SYS_PLL1_800M]);
> -	clk_hw_set_parent(hws[IMX8MN_CLK_A53_CORE], hws[IMX8MN_ARM_PLL_OUT]);
> -
>  	hws[IMX8MN_CLK_ARM] = imx_clk_hw_cpu("arm", "arm_a53_core",
>  					   hws[IMX8MN_CLK_A53_CORE]->clk,
>  					   hws[IMX8MN_CLK_A53_CORE]->clk,
>  					   hws[IMX8MN_ARM_PLL_OUT]->clk,
>  					   hws[IMX8MN_CLK_A53_DIV]->clk);
>  
> +	clk_hw_set_parent(hws[IMX8MN_CLK_A53_SRC], hws[IMX8MN_SYS_PLL1_800M]);
> +	clk_hw_set_parent(hws[IMX8MN_CLK_A53_CORE], hws[IMX8MN_ARM_PLL_OUT]);
> +
>  	imx_check_clk_hws(hws, IMX8MN_CLK_END);
>  
>  	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get, clk_hw_data);
> -- 
> 2.7.4
>