From: Maxime Ripard <maxime.ripard@free-electrons.com>
To: Olliver Schinagl <oliver@schinagl.nl>
Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>,
Thierry Reding <thierry.reding@gmail.com>,
Chen-Yu Tsai <wens@csie.org>,
linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Olliver Schinagl <o.schinagl@ultimaker.com>
Subject: Re: [PATCH 2/2] pwm: sunxi: Yield some time to the pwm-block to become ready
Date: Sat, 27 Aug 2016 00:25:23 +0200 [thread overview]
Message-ID: <20160826222523.GH3165@lukather> (raw)
In-Reply-To: <1472147411-30424-3-git-send-email-oliver@schinagl.nl>
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Hi,
On Thu, Aug 25, 2016 at 07:50:11PM +0200, Olliver Schinagl wrote:
> From: Olliver Schinagl <o.schinagl@ultimaker.com>
>
> The pwm-block of some of the sunxi chips feature a 'ready' flag to
> indicate the software that it is ready for new commands.
>
> Right now, when we call pwm_config and set the period, we write the
> values to the registers, and turn off the clock to the IP. Because of
> this, the hardware does not have time to configure the hardware and set
> the 'ready' flag.
>
> By running the clock just before making new changes and before checking
> if the hardware is ready, the hardware has time to reconfigure itself
> and set the clear the flag appropriately.
>
> Signed-off-by: Olliver Schinagl <o.schinagl@ultimaker.com>
> ---
> drivers/pwm/pwm-sun4i.c | 43 +++++++++++++++++++++++++------------------
> 1 file changed, 25 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 5e97c8a..dd198c3 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -105,6 +105,22 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> u64 clk_rate, div = 0;
> unsigned int prescaler = 0;
> int err;
> + int ret = 0;
> +
> + /* Let the PWM hardware run before making any changes. We do this to
> + * allow the hardware to have some time to clear the 'ready' flag.
> + */
This is not the proper comment style.
> + err = clk_prepare_enable(sun4i_pwm->clk);
> + if (err) {
> + dev_err(chip->dev, "failed to enable PWM clock\n");
> + return err;
> + }
New line please.
> + spin_lock(&sun4i_pwm->ctrl_lock);
> + val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
> + clk_gate = val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
> + val |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
What are you doing here? You clear a bit, and then put the same one
back in?
> + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG);
> + spin_unlock(&sun4i_pwm->ctrl_lock);
>
> clk_rate = clk_get_rate(sun4i_pwm->clk);
>
> @@ -137,7 +153,9 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>
> if (div - 1 > PWM_PRD_MASK) {
> dev_err(chip->dev, "period exceeds the maximum value\n");
> - return -EINVAL;
> + ret = -EINVAL;
> + spin_lock(&sun4i_pwm->ctrl_lock);
Uh? That's really suspicious. And even if right, please don't do that,
this is just really bad for the comprehension of the workflow.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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prev parent reply other threads:[~2016-08-26 22:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-25 17:50 [PATCHv2 0/2] pwm: sunxi: give the pwm IP block more time Olliver Schinagl
2016-08-25 17:50 ` [PATCH 1/2] pwm: sunxi: allow the pwm to finish its pulse before disable Olliver Schinagl
2016-08-26 22:19 ` Maxime Ripard
2016-09-06 7:12 ` Olliver Schinagl
2016-09-06 19:51 ` Maxime Ripard
2016-09-09 9:01 ` Olliver Schinagl
2016-09-24 20:25 ` Maxime Ripard
2016-09-26 8:46 ` Olliver Schinagl
2016-09-27 20:16 ` Maxime Ripard
[not found] ` <afcb938d-d2df-4740-6c85-cdf2766f671c@schinagl.nl>
2016-12-12 12:24 ` Maxime Ripard
2017-01-03 15:59 ` Olliver Schinagl
2017-01-03 16:55 ` Alexandre Belloni
2017-01-04 6:36 ` Thierry Reding
2016-09-23 14:02 ` [1/2] " Jonathan Liu
2016-09-23 14:03 ` Olliver Schinagl
2017-05-05 1:54 ` Jonathan Liu
2016-08-25 17:50 ` [PATCH 2/2] pwm: sunxi: Yield some time to the pwm-block to become ready Olliver Schinagl
2016-08-26 22:25 ` Maxime Ripard [this message]
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