From: Biju Das <biju.das.jz@bp.renesas.com>

The rzg2l_gpt_config() test the rzg2l_gpt->period_tick variable. This
check is not valid, if enabling of a channel happens after disabling all
the channels as it test against the cached value. Therefore, reinitialize
the variable rzg2l_gpt->period_tick to 0 in rzg2l_gpt_disable(), when
all the logical channels of a hardware channel is disabled.

Cc: stable@kernel.org
Fixes: 061f087f5d0b ("pwm: Add support for RZ/G2L GPT")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v3->v4:
 * Split the patch as separate from [1] for easy merging.
 * Updated commit description
 * Added comments about the fix in rzg2l_gpt_disable()
v3:
 * New patch

[1] https://lore.kernel.org/all/20250915163637.3572-1-biju.das.jz@bp.renesas.com/#t
---
 drivers/pwm/pwm-rzg2l-gpt.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rzg2l-gpt.c b/drivers/pwm/pwm-rzg2l-gpt.c
index 360c8bf3b190..ab91bfd7da48 100644
--- a/drivers/pwm/pwm-rzg2l-gpt.c
+++ b/drivers/pwm/pwm-rzg2l-gpt.c
@@ -190,8 +190,17 @@ static void rzg2l_gpt_disable(struct rzg2l_gpt_chip *rzg2l_gpt,
 	/* Stop count, Output low on GTIOCx pin when counting stops */
 	rzg2l_gpt->channel_enable_count[ch]--;
 
-	if (!rzg2l_gpt->channel_enable_count[ch])
+	if (!rzg2l_gpt->channel_enable_count[ch]) {
 		rzg2l_gpt_modify(rzg2l_gpt, RZG2L_GTCR(ch), RZG2L_GTCR_CST, 0);
+		/*
+		 * The rzg2l_gpt_config() test the rzg2l_gpt->period_tick
+		 * variable. This check is not valid, if enabling of a channel
+		 * happens after disabling all the channels as it test against
+		 * the cached value. Therefore, reinitialize the variable
+		 * rzg2l_gpt->period_tick to 0.
+		 */
+		rzg2l_gpt->period_ticks[ch] = 0;
+	}
 
 	/* Disable pin output */
 	rzg2l_gpt_modify(rzg2l_gpt, RZG2L_GTIOR(ch), RZG2L_GTIOR_OxE(sub_ch), 0);
-- 
2.43.0

Hello Biju,

On Fri, Nov 14, 2025 at 02:56:01PM +0000, Biju wrote:
> From: Biju Das <biju.das.jz@bp.renesas.com>
> 
> The rzg2l_gpt_config() test the rzg2l_gpt->period_tick variable. This
> check is not valid, if enabling of a channel happens after disabling all
> the channels as it test against the cached value. Therefore, reinitialize
> the variable rzg2l_gpt->period_tick to 0 in rzg2l_gpt_disable(), when
> all the logical channels of a hardware channel is disabled.
> 
> Cc: stable@kernel.org
> Fixes: 061f087f5d0b ("pwm: Add support for RZ/G2L GPT")
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> v3->v4:
>  * Split the patch as separate from [1] for easy merging.
>  * Updated commit description
>  * Added comments about the fix in rzg2l_gpt_disable()
> v3:
>  * New patch
> 
> [1] https://lore.kernel.org/all/20250915163637.3572-1-biju.das.jz@bp.renesas.com/#t
> ---
>  drivers/pwm/pwm-rzg2l-gpt.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-rzg2l-gpt.c b/drivers/pwm/pwm-rzg2l-gpt.c
> index 360c8bf3b190..ab91bfd7da48 100644
> --- a/drivers/pwm/pwm-rzg2l-gpt.c
> +++ b/drivers/pwm/pwm-rzg2l-gpt.c
> @@ -190,8 +190,17 @@ static void rzg2l_gpt_disable(struct rzg2l_gpt_chip *rzg2l_gpt,
>  	/* Stop count, Output low on GTIOCx pin when counting stops */
>  	rzg2l_gpt->channel_enable_count[ch]--;
>  
> -	if (!rzg2l_gpt->channel_enable_count[ch])
> +	if (!rzg2l_gpt->channel_enable_count[ch]) {
>  		rzg2l_gpt_modify(rzg2l_gpt, RZG2L_GTCR(ch), RZG2L_GTCR_CST, 0);
> +		/*
> +		 * The rzg2l_gpt_config() test the rzg2l_gpt->period_tick
> +		 * variable. This check is not valid, if enabling of a channel
> +		 * happens after disabling all the channels as it test against
> +		 * the cached value. Therefore, reinitialize the variable
> +		 * rzg2l_gpt->period_tick to 0.
> +		 */
> +		rzg2l_gpt->period_ticks[ch] = 0;
> +	}

I think this is wrong. rzg2l_gpt_config() has:

        if (rzg2l_gpt->channel_request_count[ch] > 1) {
                if (period_ticks < rzg2l_gpt->period_ticks[ch])
                        return -EBUSY;
                else
                        period_ticks = rzg2l_gpt->period_ticks[ch];
        }

So if both PWMs of channel `ch` are requested but disabled,
rzg2l_gpt->period_ticks[ch] is 0 so you assign

	period_ticks = rzg2l_gpt->period_ticks[ch];

. In that case however you don't want to change period_ticks, right?

Best regards
Uwe