linux-kernel - Re: [PATCH v8 13/21] clk: tegra210: Use fence

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Date:   Sun, 11 Aug 2019 21:02:02 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, tglx@...utronix.de,
        jason@...edaemon.net, marc.zyngier@....com,
        linus.walleij@...aro.org, stefan@...er.ch, mark.rutland@....com
Cc:     pdeschrijver@...dia.com, pgaikwad@...dia.com, sboyd@...nel.org,
        linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
        jckuo@...dia.com, josephl@...dia.com, talho@...dia.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        mperttunen@...dia.com, spatra@...dia.com, robh+dt@...nel.org,
        devicetree@...r.kernel.org, rjw@...ysocki.net,
        viresh.kumar@...aro.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v8 13/21] clk: tegra210: Use fence_udelay during PLLU init

09.08.2019 2:46, Sowjanya Komatineni пишет:
> This patch uses fence_udelay rather than udelay during PLLU
> initialization to ensure writes to clock registers happens before
> waiting for specified delay.
> 
> Acked-by: Thierry Reding <treding@...dia.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/clk/tegra/clk-tegra210.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
> index 4721ee030d1c..998bf60b219a 100644
> --- a/drivers/clk/tegra/clk-tegra210.c
> +++ b/drivers/clk/tegra/clk-tegra210.c
> @@ -2841,7 +2841,7 @@ static int tegra210_enable_pllu(void)
>  	reg = readl_relaxed(clk_base + pllu.params->ext_misc_reg[0]);
>  	reg &= ~BIT(pllu.params->iddq_bit_idx);
>  	writel_relaxed(reg, clk_base + pllu.params->ext_misc_reg[0]);
> -	udelay(5);
> +	fence_udelay(5, clk_base);
>  
>  	reg = readl_relaxed(clk_base + PLLU_BASE);
>  	reg &= ~GENMASK(20, 0);
> @@ -2849,7 +2849,7 @@ static int tegra210_enable_pllu(void)
>  	reg |= fentry->n << 8;
>  	reg |= fentry->p << 16;
>  	writel(reg, clk_base + PLLU_BASE);
> -	udelay(1);
> +	fence_udelay(1, clk_base);
>  	reg |= PLL_ENABLE;
>  	writel(reg, clk_base + PLLU_BASE);
>  
> @@ -2895,12 +2895,12 @@ static int tegra210_init_pllu(void)
>  		reg = readl_relaxed(clk_base + XUSB_PLL_CFG0);
>  		reg &= ~XUSB_PLL_CFG0_PLLU_LOCK_DLY_MASK;
>  		writel_relaxed(reg, clk_base + XUSB_PLL_CFG0);
> -		udelay(1);
> +		fence_udelay(1, clk_base);
>  
>  		reg = readl_relaxed(clk_base + PLLU_HW_PWRDN_CFG0);
>  		reg |= PLLU_HW_PWRDN_CFG0_SEQ_ENABLE;
>  		writel_relaxed(reg, clk_base + PLLU_HW_PWRDN_CFG0);
> -		udelay(1);
> +		fence_udelay(1, clk_base);
>  
>  		reg = readl_relaxed(clk_base + PLLU_BASE);
>  		reg &= ~PLLU_BASE_CLKENABLE_USB;
> 

The clk_base corresponds to the RESET controller's part of Clock-and-Reset hardware, is it
okay to read-back the RST register and not the clock for the fencing?