linux-kernel - Re: [PATCH v2] clk: tegra: divider: Check UART's divider enable-bit state on rate's recalculation

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Date:   Thu, 14 Nov 2019 12:54:24 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] clk: tegra: divider: Check UART's divider enable-bit
 state on rate's recalculation

On Wed, Oct 30, 2019 at 03:48:13AM +0300, Dmitry Osipenko wrote:
> UART clock is divided using divisor values from DLM/DLL registers when
> enable-bit is unset in clk register and clk's divider configuration isn't
> taken onto account in this case. This doesn't cause any problems, but
> let's add a check for the divider's enable-bit state, for consistency.
> 
> Acked-by: Peter De Schrijver <pdeschrijver@...dia.com>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> 
> Changelog:
> 
> v2: In the comment to v1 Peter De Schrijver pointed out that UART's DLM/DLL
>     registers configuration is used when enable bit is unset, thus the
>     commit's title and message are changed accordingly.
> 
>  drivers/clk/tegra/clk-divider.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)

Stephen, feel free to apply this on top of the Tegra pull requests:

Acked-by: Thierry Reding <treding@...dia.com>

> 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;
> -- 
> 2.23.0
> 

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