linux-kernel - Re: [PATCH] Fix IMX PWM period setting

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Message-ID: <qsc5hl22l4bxs6jzqbc43r4wxvmbwz6rpcfsiv4hcp2uzrsscy@ogjzgesvy2wl>
Date: Thu, 30 Oct 2025 18:13:41 +0100
From: Uwe Kleine-König <ukleinek@...nel.org>
To: "Krebs, Olaf" <Olaf.Krebs@...-metering.com>
Cc: Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, 
	"open list:PWM SUBSYSTEM" <linux-pwm@...r.kernel.org>, 
	"open list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <imx@...ts.linux.dev>, 
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix IMX PWM period setting

Hello,

please version your patch revision, i.e. you should have put "v2" in the
subject. The easiest way to achieve that is by passing -v2 to `git
format-patch` (or `git send-email` if you use that directly). So for the
next revision use -v3.

On Thu, Oct 30, 2025 at 11:53:27AM +0000, Krebs, Olaf wrote:
> From: Olaf Krebs <okr@...w.emh-meter.de>
> 
> We use 3 PWM channels to control an RGB LED. Without this patch, an BUSY-error message is generated during initialization.
> 
> [    7.395326] leds_pwm_multicolor led-controller: error -EBUSY: failed to set led PWM value for (null)
> [    7.405167] leds_pwm_multicolor led-controller: probe with driver leds_pwm_multicolor failed with error -16
> 
> Our DTS-Config for an imx93-Board:
> 	...
> 	led-controller {
> 		compatible = "pwm-leds-multicolor";
> 		multi-led {
> 			label = "RGBled";
> 			color = <LED_COLOR_ID_RGB>;
> 			function = LED_FUNCTION_INDICATOR;
> 			max-brightness = <255>;
> 			led-red {
> 				pwms = <&tpm5 0 1000000 PWM_POLARITY_INVERTED>;
> 				color = <LED_COLOR_ID_RED>;
> 			};
> 			led-green {
> 				pwms = <&tpm6 2 1000000 PWM_POLARITY_INVERTED>;
> 				color = <LED_COLOR_ID_GREEN>;
> 			};
> 			led-blue {
> 				pwms = <&tpm5 1 1000000 PWM_POLARITY_INVERTED>;
> 				color = <LED_COLOR_ID_BLUE>;
> 			};
> 		};
> 	};
> 	...

I would prefer something like the following text here:

	If a second PWM is requested by a driver before the first is
	configured, trying to configure any of these results in
	.user_count > 1 and thus the configuration fails. 
	Fix that by only erroring out by additionally checking if the
	period is actually configured.

> Signed-off-by: Olaf krebs <olaf.krebs@...-metering.com>

S-o-b missmatch. Do you know checkpatch? That one also wails:
WARNING: Prefer a maximum 75 chars per line (possible unwrapped commit description?)

> ---
>  drivers/pwm/pwm-imx-tpm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c index 5b399de16d60..411daa7711f1 100644
> --- a/drivers/pwm/pwm-imx-tpm.c
> +++ b/drivers/pwm/pwm-imx-tpm.c
> @@ -190,7 +190,7 @@ static int pwm_imx_tpm_apply_hw(struct pwm_chip *chip,
>  		 * there are multiple channels in use with different
>  		 * period settings.
>  		 */
> -		if (tpm->user_count > 1)
> +		if ((tpm->user_count > 1) && (tpm->real_period != 0))
>  			return -EBUSY;

Please drop the added parenthesis.

Thinking about the error here, I wonder if a saner check would involve
enable_count instead of user_count.

>  		val = readl(tpm->base + PWM_IMX_TPM_SC);

Best regards
Uwe

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