linux-kernel - Re: [PATCH 4/8] pwm: dwc: add of/platform support

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Date:   Sat, 6 Aug 2022 11:29:58 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Ben Dooks <ben.dooks@...ive.com>
Cc:     linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Greentime Hu <greentime.hu@...ive.com>,
        jarkko.nikula@...ux.intel.com,
        William Salmon <william.salmon@...ive.com>,
        Jude Onyenegecha --subject-prefix=PATCH v3 
        <jude.onyenegecha@...ive.com>
Subject: Re: [PATCH 4/8] pwm: dwc: add of/platform support

On Fri, Aug 05, 2022 at 05:50:29PM +0100, Ben Dooks wrote:
> The dwc pwm controller can be used in non-PCI systems, so allow
> either platform or OF based probing.
> 
> Signed-off-by: Ben Dooks <ben.dooks@...ive.com>
> ---
> v3:
>  - changed compatible name
> ---
>  drivers/pwm/Kconfig   |  5 ++--
>  drivers/pwm/pwm-dwc.c | 53 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 60d13a949bc5..b8717877a524 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -176,9 +176,10 @@ config PWM_CROS_EC
>  
>  config PWM_DWC
>  	tristate "DesignWare PWM Controller"
> -	depends on PCI
> +	depends on PCI || OF
>  	help
> -	  PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
> +	  PWM driver for Synopsys DWC PWM Controller attached to either a
> +	  PCI or platform bus.
>  
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-dwc.
> diff --git a/drivers/pwm/pwm-dwc.c b/drivers/pwm/pwm-dwc.c
> index 61f11e0a9319..d5f2df6fee62 100644
> --- a/drivers/pwm/pwm-dwc.c
> +++ b/drivers/pwm/pwm-dwc.c
> @@ -18,6 +18,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/pwm.h>
>  
> @@ -319,6 +320,58 @@ static struct pci_driver dwc_pwm_driver = {
>  
>  module_pci_driver(dwc_pwm_driver);
>  
> +#ifdef CONFIG_OF
> +static int dwc_pwm_plat_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct dwc_pwm *dwc;
> +	int ret;
> +
> +	dwc = dwc_pwm_alloc(dev);
> +	if (!dwc)
> +		return -ENOMEM;
> +
> +	dwc->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(dwc->base))
> +		return dev_err_probe(dev, PTR_ERR(dwc->base),
> +				     "failed to map IO\n");

devm_platform_ioremap_resource already provides an error message, so
drop the message here.

> +	ret = pwmchip_add(&dwc->chip);
> +	if (ret)
> +		return ret;
> +
> +	return 0;

the last three code lines are equivalent to just

	return ret;

An error message would be nice after pwmchip_add failed.

> +}
> +
> +static int dwc_pwm_plat_remove(struct platform_device *pdev)
> +{
> +	struct dwc_pwm *dwc = platform_get_drvdata(pdev);
> +
> +	pwmchip_remove(&dwc->chip);
> +	return 0;
> +}

Please consider using devm_pwmchip_add() which makes it unnecessary to
provide a remove callback.

> +static const struct of_device_id dwc_pwm_dt_ids[] = {
> +	{ .compatible = "snps,dw-apb-timers-pwm2" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, dwc_pwm_dt_ids);
> +
> +static struct platform_driver dwc_pwm_plat_driver = {
> +	.driver = {
> +		.name		= "dwc-pwm",
> +		.of_match_table  = dwc_pwm_dt_ids,

I'm not a fan of aligning the = signs, for sure, don't use tabs for one
and spaces for the other. If you ask me, use a single space.

> +	},
> +	.probe	= dwc_pwm_plat_probe,
> +	.remove	= dwc_pwm_plat_remove,
> +};
> +
> +module_platform_driver(dwc_pwm_plat_driver);
> +
> +MODULE_ALIAS("platform:dwc-pwm");
> +#endif /* CONFIG_OF */
> +
> +
>  MODULE_AUTHOR("Felipe Balbi (Intel)");
>  MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@...ux.intel.com>");
>  MODULE_AUTHOR("Raymond Tan <raymond.tan@...el.com>");
> 

Best regards
Uwe

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

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