| Message ID | 1445895161-2317-4-git-send-email-o.schinagl@ultimaker.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Oct 26, 2015 at 10:32:34PM +0100, Olliver Schinagl wrote: > 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(-) This looks okay to me (except for one minor thing I noticed, see below), but I'd like an Acked-by from one of the sunxi people. Maxime, any comments on this? > diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c > index 58ff424..4d84d9d 100644 > --- a/drivers/pwm/pwm-sun4i.c > +++ b/drivers/pwm/pwm-sun4i.c > @@ -104,6 +104,22 @@ 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; Why not reuse err? Thierry
On Tue, Oct 27, 2015 at 5:32 AM, Olliver Schinagl <o.schinagl@ultimaker.com> wrote: > 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 58ff424..4d84d9d 100644 > --- a/drivers/pwm/pwm-sun4i.c > +++ b/drivers/pwm/pwm-sun4i.c > @@ -104,6 +104,22 @@ 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. > + */ > + err = clk_prepare_enable(sun4i_pwm->clk); > + if (err) { > + dev_err(chip->dev, "failed to enable PWM clock\n"); > + return err; > + } > + 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); > + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); > + spin_unlock(&sun4i_pwm->ctrl_lock); > > clk_rate = clk_get_rate(sun4i_pwm->clk); > > @@ -136,7 +152,9 @@ 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); > + goto out; > } > } > > @@ -145,26 +163,14 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > do_div(div, period_ns); > dty = div; > > - err = clk_prepare_enable(sun4i_pwm->clk); > - if (err) { > - dev_err(chip->dev, "failed to enable PWM clock\n"); > - return err; > - } > - > spin_lock(&sun4i_pwm->ctrl_lock); > val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); > - > if (sun4i_pwm->data->has_rdy && (val & PWM_RDY(pwm->hwpwm))) { Instead of moving the code around to try to give the hardware some unspecified time to run, could we use a tight busy loop with a timeout to read the register and check if it's been cleared? I think that works better with cpufreq as well. Thanks. ChenYu > - spin_unlock(&sun4i_pwm->ctrl_lock); > - clk_disable_unprepare(sun4i_pwm->clk); > - return -EBUSY; > - } > - > - clk_gate = val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm); > - if (clk_gate) { > - val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm); > - sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); > + ret = -EBUSY; > + goto out; > } > + val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm); > + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); > > val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); > val &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm); > @@ -174,6 +180,7 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > val = (dty & PWM_DTY_MASK) | PWM_PRD(prd); > sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm)); > > +out: > if (clk_gate) { > val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); > val |= clk_gate; > @@ -183,7 +190,7 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > spin_unlock(&sun4i_pwm->ctrl_lock); > clk_disable_unprepare(sun4i_pwm->clk); > > - return 0; > + return ret; > } > > static int sun4i_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm, > -- > 2.6.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c index 58ff424..4d84d9d 100644 --- a/drivers/pwm/pwm-sun4i.c +++ b/drivers/pwm/pwm-sun4i.c @@ -104,6 +104,22 @@ 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. + */ + err = clk_prepare_enable(sun4i_pwm->clk); + if (err) { + dev_err(chip->dev, "failed to enable PWM clock\n"); + return err; + } + 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); + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); + spin_unlock(&sun4i_pwm->ctrl_lock); clk_rate = clk_get_rate(sun4i_pwm->clk); @@ -136,7 +152,9 @@ 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); + goto out; } } @@ -145,26 +163,14 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, do_div(div, period_ns); dty = div; - err = clk_prepare_enable(sun4i_pwm->clk); - if (err) { - dev_err(chip->dev, "failed to enable PWM clock\n"); - return err; - } - spin_lock(&sun4i_pwm->ctrl_lock); val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); - if (sun4i_pwm->data->has_rdy && (val & PWM_RDY(pwm->hwpwm))) { - spin_unlock(&sun4i_pwm->ctrl_lock); - clk_disable_unprepare(sun4i_pwm->clk); - return -EBUSY; - } - - clk_gate = val & BIT_CH(PWM_CLK_GATING, pwm->hwpwm); - if (clk_gate) { - val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm); - sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); + ret = -EBUSY; + goto out; } + val &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm); + sun4i_pwm_writel(sun4i_pwm, val, PWM_CTRL_REG); val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); val &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm); @@ -174,6 +180,7 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, val = (dty & PWM_DTY_MASK) | PWM_PRD(prd); sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm)); +out: if (clk_gate) { val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG); val |= clk_gate; @@ -183,7 +190,7 @@ static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, spin_unlock(&sun4i_pwm->ctrl_lock); clk_disable_unprepare(sun4i_pwm->clk); - return 0; + return ret; } static int sun4i_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
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(-)