linux-kernel - Re: [PATCH 12/13] pwm: jz4740: Let the pinctrl driver configure the pins

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Date:   Wed, 18 Jan 2017 08:20:18 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Maarten ter Huurne <maarten@...ewalker.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Paul Burton <paul.burton@...tec.com>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
        linux-mmc@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        james.hogan@...tec.com
Subject: Re: [PATCH 12/13] pwm: jz4740: Let the pinctrl driver configure the
 pins

On Wed, Jan 18, 2017 at 12:14:20AM +0100, Paul Cercueil wrote:
> Now that the JZ4740 and similar SoCs have a pinctrl driver, we rely on
> the pins being properly configured before the driver probes.
> 
> One inherent problem of this new approach is that the pinctrl framework
> does not allow us to configure each pin on demand, when the various PWM
> channels are requested or released. For instance, the PWM channels can
> be configured from sysfs, which would require all PWM pins to be configured
> properly beforehand for the PWM function, eventually causing conflicts
> with other platform or board drivers.
> 
> The proper solution here would be to modify the pwm-jz4740 driver to
> handle only one PWM channel, and create an instance of this driver
> for each one of the 8 PWM channels. Then, it could use the pinctrl
> framework to dynamically configure the PWM pin it controls.
> 
> Until this can be done, the only jz4740 board supported upstream
> (Qi lb60) could configure all of its connected PWM pins in PWM function
> mode, if those are not used by other drivers nor by GPIOs on the
> board.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/pwm/pwm-jz4740.c | 29 -----------------------------
>  1 file changed, 29 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
> index 76d13150283f..a75ff3622450 100644
> --- a/drivers/pwm/pwm-jz4740.c
> +++ b/drivers/pwm/pwm-jz4740.c
> @@ -21,22 +21,10 @@
>  #include <linux/platform_device.h>
>  #include <linux/pwm.h>
>  
> -#include <asm/mach-jz4740/gpio.h>

What about the linux/gpio.h header? It seems to me like that would be no
longer needed after this patch either.

Other than that this looks like the patch I'd expect if the pinmux was
configured statically, based on board design.

Thierry

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