linux-kernel - Re: [PATCH v3] pwm: mediatek: fix up PWM4 and PWM5 malfunction on MT7623

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Message-ID: <20180302105719.GC27178@ulmo>
Date:   Fri, 2 Mar 2018 11:57:19 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     sean.wang@...iatek.com
Cc:     matthias.bgg@...il.com, linux-pwm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Zhi Mao <zhi.mao@...iatek.com>,
        John Crispin <john@...ozen.org>
Subject: Re: [PATCH v3] pwm: mediatek: fix up PWM4 and PWM5 malfunction on
 MT7623

On Thu, Mar 01, 2018 at 04:19:12PM +0800, sean.wang@...iatek.com wrote:
> From: Sean Wang <sean.wang@...iatek.com>
> 
> Since the offset for both registers, PWMDWIDTH and PWMTHRES, used to
> control PWM4 or PWM5 are distinct from the other PWMs, whose wrong
> programming on PWM hardware causes waveform cannot be output as expected.
> Thus, the patch adds the extra condition for fixing up the weird case to
> let PWM4 or PWM5 able to work on MT7623.
> 
> v1 -> v2: use pwm45_fixup naming instead of pwm45_quirk
> v2 -> v3: add more tags for Reviewed-by, Fixes, and Cc stable
> 
> Cc: stable@...r.kernel.org
> Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
> Cc: Zhi Mao <zhi.mao@...iatek.com>
> Cc: John Crispin <john@...ozen.org>
> Cc: Matthias Brugger <matthias.bgg@...il.com>
> ---
>  drivers/pwm/pwm-mediatek.c | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
[...]
> @@ -151,9 +156,18 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  		return -EINVAL;
>  	}
>  
> +	if (pc->soc->pwm45_fixup && pwm->hwpwm > 2) {
> +		/*
> +		 * PWM[4,5] has distinct offset for PWMDWIDTH and PWMTHRES
> +		 * from the other PWMs on MT7623.
> +		 */
> +		reg_width = PWM45DWIDTH_FIXUP;
> +		reg_thres = PWM45THRES_FIXUP;
> +	}

I don't understand this. According to the condition above the above
would also use the PWM[4,5] "fixup" register offsets with PWM[3]. Should
the condition be pwm->hwpwm > 3?

Thierry

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