From: Samuel Holland <samuel@sholland.org>
To: dev@pascalroeleven.nl,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Maxime Ripard" <mripard@kernel.org>,
"Chen-Yu Tsai" <wens@csie.org>,
"Philipp Zabel" <p.zabel@pengutronix.de>,
linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Cc: linux-sunxi@googlegroups.com
Subject: Re: [linux-sunxi] [RFC PATCH 4/4] pwm: sun4i: Delay after writing the period
Date: Tue, 21 Apr 2020 22:43:37 -0500 [thread overview]
Message-ID: <f1d9a17e-df9e-dc12-603d-84e908a04b81@sholland.org> (raw)
In-Reply-To: <20200317155906.31288-5-dev@pascalroeleven.nl>
Hello Pascal,
On 3/17/20 10:59 AM, Pascal Roeleven wrote:
> When disabling, ensure the period write is complete before continuing.
> This fixes an issue on some devices when the write isn't complete before
> the panel is turned off but the clock gate is still on.
>
> Signed-off-by: Pascal Roeleven <dev@pascalroeleven.nl>
> ---
> drivers/pwm/pwm-sun4i.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index a11d00f96..75250fd4c 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -299,6 +299,10 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
> next_period = jiffies + usecs_to_jiffies(cstate.period / 1000 + 1);
>
> + /* When disabling, make sure the period register is written first */
> + if (!state->enabled && cstate.enabled)
> + sun4i_pwm_wait(next_period);
> +
It is not visible from the context of this patch, but this call to
sun4i_pwm_wait() ends up calling msleep() inside a spinlock, which isn't
allowed. The spinlock should probably be converted to a mutex, considering that
sun4i_pwm_apply() already sleeps and takes mutexes.
Regards,
Samuel
> if (state->polarity != PWM_POLARITY_NORMAL)
> ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
> else
> @@ -320,6 +324,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> return 0;
>
> /* We need a full period to elapse before disabling the channel. */
> + next_period = jiffies + usecs_to_jiffies(cstate.period / 1000 + 1);
> sun4i_pwm_wait(next_period);
>
> spin_lock(&sun4i_pwm->ctrl_lock);
>
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next prev parent reply other threads:[~2020-04-22 3:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 15:59 [RFC PATCH 0/4] pwm: sun4i: Properly turn pwm off and fix stuck output state Pascal Roeleven
2020-03-17 15:59 ` [RFC PATCH 1/4] pwm: sun4i: Remove redundant needs_delay Pascal Roeleven
2020-03-30 14:16 ` Thierry Reding
2020-03-17 15:59 ` [RFC PATCH 2/4] pwm: sun4i: Disable pwm before turning off clock gate Pascal Roeleven
2020-04-09 15:19 ` Chen-Yu Tsai
2020-03-17 15:59 ` [RFC PATCH 3/4] pwm: sun4i: Move delay to function Pascal Roeleven
2020-04-09 15:20 ` [linux-sunxi] " Chen-Yu Tsai
2020-03-17 15:59 ` [RFC PATCH 4/4] pwm: sun4i: Delay after writing the period Pascal Roeleven
2020-04-09 15:20 ` Chen-Yu Tsai
2020-04-22 3:43 ` Samuel Holland [this message]
2020-04-22 8:40 ` [linux-sunxi] " Pascal Roeleven
2020-03-17 16:45 ` [RFC PATCH 0/4] pwm: sun4i: Properly turn pwm off and fix stuck output state Emil Lenngren
2020-03-17 18:15 ` Pascal Roeleven
2020-03-17 19:35 ` Emil Lenngren
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