linux-kernel - Re: [PATCH v2 1/2] clk: tegra: divider: Add missing check for enable-bit on rate's recalculation

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Date:   Mon, 23 Sep 2019 00:47:21 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        linux-clk@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] clk: tegra: divider: Add missing check for
 enable-bit on rate's recalculation

23.07.2019 5:52, Dmitry Osipenko пишет:
> Unset "enable" bit means that divider is in bypass mode, hence it doesn't
> have any effect in that case. Please note that there are no known bugs
> caused by the missing check.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> 
> Changelog:
> 
> v2: Changed the commit's description from 'Fix' to 'Add' in response to the
>     Stephen's Boyd question about the need to backport the patch into stable
>     kernels. The backporting is not really needed.
> 
>  drivers/clk/tegra/clk-divider.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c
> index e76731fb7d69..f33c19045386 100644
> --- a/drivers/clk/tegra/clk-divider.c
> +++ b/drivers/clk/tegra/clk-divider.c
> @@ -40,8 +40,13 @@ static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw,
>  	int div, mul;
>  	u64 rate = parent_rate;
>  
> -	reg = readl_relaxed(divider->reg) >> divider->shift;
> -	div = reg & div_mask(divider);
> +	reg = readl_relaxed(divider->reg);
> +
> +	if ((divider->flags & TEGRA_DIVIDER_UART) &&
> +	    !(reg & PERIPH_CLK_UART_DIV_ENB))
> +		return rate;
> +
> +	div = (reg >> divider->shift) & div_mask(divider);
>  
>  	mul = get_mul(divider);
>  	div += mul;
> 

Hello Peter,

ACK?