linux-kernel - Re: [PATCH v5 3/8] pwm: sun4i: Prefer "mod" clock to unnamed

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Date:   Mon, 18 Nov 2019 10:50:00 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Philipp Zabel <pza@...gutronix.de>, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v5 3/8] pwm: sun4i: Prefer "mod" clock to unnamed

On Mon, Nov 18, 2019 at 10:37:22AM +0100, Clément Péron wrote:
> New device tree bindings called the source clock of the module
> "mod" when several clocks are defined.
> 
> Try to get a clock called "mod" if nothing is found try to get
> an unnamed clock.
> 
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> ---
>  drivers/pwm/pwm-sun4i.c | 29 +++++++++++++++++++++++++++--
>  1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index c17935805690..bbb1ed194c0e 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -362,9 +362,34 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
>  	if (IS_ERR(pwm->base))
>  		return PTR_ERR(pwm->base);
>  
> -	pwm->clk = devm_clk_get(&pdev->dev, NULL);
> -	if (IS_ERR(pwm->clk))
> +	/*
> +	 * All hardware variants need a source clock that is divided and
> +	 * then feeds the counter that defines the output wave form. In the
> +	 * device tree this clock is either unnamed or called "mod".
> +	 * Some variants (e.g. H6) need another clock to access the
> +	 * hardware registers; this is called "bus".
> +	 * So we request "mod" first (and ignore the corner case that a
> +	 * parent provides a "mod" clock while the right one would be the
> +	 * unnamed one of the PWM device) and if this is not found we fall
> +	 * back to the first clock of the PWM.
> +	 */
> +	pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
> +	if (IS_ERR(pwm->clk)) {
> +		if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "get clock failed %pe\n",
> +				pwm->clk);

I think the line break isn't needed here. Unless I'm mistaken the final
; will end in column 80 which is fine.

>  		return PTR_ERR(pwm->clk);
> +	}
> +
> +	if (!pwm->clk) {
> +		pwm->clk = devm_clk_get(&pdev->dev, NULL);
> +		if (IS_ERR(pwm->clk)) {
> +			if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> +				dev_err(&pdev->dev, "get clock failed %pe\n",
> +					pwm->clk);

A different error message than above would be nice to be able to
distinguish the two cases.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |