| Message ID | 20230429104534.28943-3-aweber.kernel@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | video: backlight: lp855x: modernize bindings | expand |
On Sat, Apr 29, 2023 at 12:45:32PM +0200, Artur Weber wrote: > Also deprecate the pwm-period DT property, as it is now redundant > (pwms property already contains period value). > > Signed-off-by: Artur Weber <aweber.kernel@gmail.com> > --- > drivers/video/backlight/lp855x_bl.c | 48 ++++++++++++++++------------- > 1 file changed, 26 insertions(+), 22 deletions(-) > > diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c > index 81012bf29baf..21eb4943ed56 100644 > --- a/drivers/video/backlight/lp855x_bl.c > +++ b/drivers/video/backlight/lp855x_bl.c > @@ -218,23 +218,10 @@ static int lp855x_configure(struct lp855x *lp) > > static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br) > { > - struct pwm_device *pwm; > struct pwm_state state; > > - /* request pwm device with the consumer name */ > - if (!lp->pwm) { > - pwm = devm_pwm_get(lp->dev, lp->chipname); > - if (IS_ERR(pwm)) > - return; > - > - lp->pwm = pwm; > - > - pwm_init_state(lp->pwm, &state); > - } else { > - pwm_get_state(lp->pwm, &state); > - } > + pwm_get_state(lp->pwm, &state); pwm_get_state returns an error code. Do you care if it fails? (You probably should.) > > - state.period = lp->pdata->period_ns; > state.duty_cycle = div_u64(br * state.period, max_br); > state.enabled = state.duty_cycle; > > @@ -339,6 +326,7 @@ static int lp855x_parse_dt(struct lp855x *lp) > of_property_read_string(node, "bl-name", &pdata->name); > of_property_read_u8(node, "dev-ctrl", &pdata->device_control); > of_property_read_u8(node, "init-brt", &pdata->initial_brightness); > + /* Deprecated, specify period in pwms property instead */ > of_property_read_u32(node, "pwm-period", &pdata->period_ns); > > /* Fill ROM platform data if defined */ > @@ -399,6 +387,7 @@ static int lp855x_probe(struct i2c_client *cl) > const struct i2c_device_id *id = i2c_client_get_device_id(cl); > const struct acpi_device_id *acpi_id = NULL; > struct device *dev = &cl->dev; > + struct pwm_state pwmstate; > struct lp855x *lp; > int ret; > > @@ -457,11 +446,6 @@ static int lp855x_probe(struct i2c_client *cl) > } > } > > - if (lp->pdata->period_ns > 0) > - lp->mode = PWM_BASED; > - else > - lp->mode = REGISTER_BASED; > - > lp->supply = devm_regulator_get(dev, "power"); > if (IS_ERR(lp->supply)) { > if (PTR_ERR(lp->supply) == -EPROBE_DEFER) > @@ -472,11 +456,31 @@ static int lp855x_probe(struct i2c_client *cl) > lp->enable = devm_regulator_get_optional(dev, "enable"); > if (IS_ERR(lp->enable)) { > ret = PTR_ERR(lp->enable); > - if (ret == -ENODEV) { > + if (ret == -ENODEV) > lp->enable = NULL; > - } else { > + else > return dev_err_probe(dev, ret, "getting enable regulator\n"); > - } > + } > + > + lp->pwm = devm_pwm_get(lp->dev, lp->chipname); > + if (IS_ERR(lp->pwm)) { > + ret = PTR_ERR(lp->pwm); > + if (ret == -ENODEV || ret == -EINVAL) Why would you ignore EINVAL? > + lp->pwm = NULL; > + else > + return dev_err_probe(dev, ret, "getting PWM\n"); > + > + lp->mode = REGISTER_BASED; > + dev_dbg(dev, "mode: register based\n"); > + } else { pwmstate could be declared here. > + pwm_init_state(lp->pwm, &pwmstate); > + /* Legacy platform data compatibility */ > + if (lp->pdata->period_ns > 0) > + pwmstate.period = lp->pdata->period_ns; > + pwm_apply_state(lp->pwm, &pwmstate); This is a change in behaviour. Before lp855x_probe() didn't modify the state the bootloader left the backlight in. Now you're disabling it (I think). Is this intended? Best regards Uwe
On 14/06/2023 10:39, Uwe Kleine-König wrote: > On Sat, Apr 29, 2023 at 12:45:32PM +0200, Artur Weber wrote: >> Also deprecate the pwm-period DT property, as it is now redundant >> (pwms property already contains period value). >> >> Signed-off-by: Artur Weber <aweber.kernel@gmail.com> >> --- >> drivers/video/backlight/lp855x_bl.c | 48 ++++++++++++++++------------- >> 1 file changed, 26 insertions(+), 22 deletions(-) >> >> diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c >> index 81012bf29baf..21eb4943ed56 100644 >> --- a/drivers/video/backlight/lp855x_bl.c >> +++ b/drivers/video/backlight/lp855x_bl.c >> ... >> @@ -472,11 +456,31 @@ static int lp855x_probe(struct i2c_client *cl) >> lp->enable = devm_regulator_get_optional(dev, "enable"); >> if (IS_ERR(lp->enable)) { >> ret = PTR_ERR(lp->enable); >> - if (ret == -ENODEV) { >> + if (ret == -ENODEV) >> lp->enable = NULL; >> - } else { >> + else >> return dev_err_probe(dev, ret, "getting enable regulator\n"); >> - } >> + } >> + >> + lp->pwm = devm_pwm_get(lp->dev, lp->chipname); >> + if (IS_ERR(lp->pwm)) { >> + ret = PTR_ERR(lp->pwm); >> + if (ret == -ENODEV || ret == -EINVAL) > > Why would you ignore EINVAL? EINVAL is returned when the pwms property is not found in the DT node for the backlight. Not sure if there's a better way of separately detecting whether it's present (especially when taking into consideration non-DT platforms that might use the driver). Would be nice to have something like devm_regulator_get_optional but for PWMs... Still, someone who's setting up the driver could check the debug messages to see if the backlight was set up in PWM mode or register mode. > ... >> + pwm_init_state(lp->pwm, &pwmstate); >> + /* Legacy platform data compatibility */ >> + if (lp->pdata->period_ns > 0) >> + pwmstate.period = lp->pdata->period_ns; >> + pwm_apply_state(lp->pwm, &pwmstate); > > This is a change in behaviour. Before lp855x_probe() didn't modify the > state the bootloader left the backlight in. Now you're disabling it (I > think). Is this intended? I didn't really consider the implication of this in this way, as on the device I was testing this on (Exynos4212-based tablet) the PWM state would get reset during PWM chip initialization in the kernel anyways, meaning that the state from the bootloader would be lost regardless of this change. Either way, there's no guarantee that this would be the same on other devices, though I'd assume that in most cases it's not noticeable anyways as brightness is usually set somewhere in userspace (or even earlier, in the driver, if the init-brt property is set). Nonetheless, that's an oversight on my part. As for the reasoning for this change in behavior - the previous behavior was to silently fail if, while setting the brightness, the PWM could not be set up. This seemed rather confusing to me (I encountered this while I was initially working on the tablet, I added a "pwm" property instead of "pwms" and was wondering why the backlight didn't work...) Of course, that could be fixed by adding error detection in the brightness set function, but since I was already working on it, it made more sense to me for the PWM to be set up during the probing process, given that this way we could 1. warn about errors early, and 2. catch deferred probes and defer the backlight's probe if we're still waiting for the PWM. That's why it's done the way it is in this patch. If this is undesired behavior, let me know and I'll submit another patch to revert it. Best regards Artur
Hello, On Fri, Jun 16, 2023 at 05:29:08PM +0200, Artur Weber wrote: > On 14/06/2023 10:39, Uwe Kleine-König wrote: > > On Sat, Apr 29, 2023 at 12:45:32PM +0200, Artur Weber wrote: > >> Also deprecate the pwm-period DT property, as it is now redundant > >> (pwms property already contains period value). > >> > >> Signed-off-by: Artur Weber <aweber.kernel@gmail.com> > >> --- > >> drivers/video/backlight/lp855x_bl.c | 48 ++++++++++++++++------------- > >> 1 file changed, 26 insertions(+), 22 deletions(-) > >> > >> diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c > >> index 81012bf29baf..21eb4943ed56 100644 > >> --- a/drivers/video/backlight/lp855x_bl.c > >> +++ b/drivers/video/backlight/lp855x_bl.c > >> ... > >> @@ -472,11 +456,31 @@ static int lp855x_probe(struct i2c_client *cl) > >> lp->enable = devm_regulator_get_optional(dev, "enable"); > >> if (IS_ERR(lp->enable)) { > >> ret = PTR_ERR(lp->enable); > >> - if (ret == -ENODEV) { > >> + if (ret == -ENODEV) > >> lp->enable = NULL; > >> - } else { > >> + else > >> return dev_err_probe(dev, ret, "getting enable regulator\n"); > >> - } > >> + } > >> + > >> + lp->pwm = devm_pwm_get(lp->dev, lp->chipname); > >> + if (IS_ERR(lp->pwm)) { > >> + ret = PTR_ERR(lp->pwm); > >> + if (ret == -ENODEV || ret == -EINVAL) > > > > Why would you ignore EINVAL? > > EINVAL is returned when the pwms property is not found in the DT node > for the backlight. Not sure if there's a better way of separately > detecting whether it's present (especially when taking into > consideration non-DT platforms that might use the driver). Would be nice > to have something like devm_regulator_get_optional but for PWMs... Ah, that is because of_pwm_get() calls of_property_match_string(np, "pwm-names", con_id) which returns -EINVAL if there is no pwm-names property. This is different for clocks. I wonder if pwm should adapt accordingly? Thierry? > Still, someone who's setting up the driver could check the debug > messages to see if the backlight was set up in PWM mode or register mode. > > > ... > >> + pwm_init_state(lp->pwm, &pwmstate); > >> + /* Legacy platform data compatibility */ > >> + if (lp->pdata->period_ns > 0) > >> + pwmstate.period = lp->pdata->period_ns; > >> + pwm_apply_state(lp->pwm, &pwmstate); > > > > This is a change in behaviour. Before lp855x_probe() didn't modify the > > state the bootloader left the backlight in. Now you're disabling it (I > > think). Is this intended? > > I didn't really consider the implication of this in this way, as on the > device I was testing this on (Exynos4212-based tablet) the PWM state > would get reset during PWM chip initialization in the kernel anyways, Which chip driver is in use here? That's a patch opportunity. > meaning that the state from the bootloader would be lost regardless of > this change. Either way, there's no guarantee that this would be the > same on other devices, though I'd assume that in most cases it's not > noticeable anyways as brightness is usually set somewhere in userspace > (or even earlier, in the driver, if the init-brt property is set). > Nonetheless, that's an oversight on my part. > > As for the reasoning for this change in behavior - the previous behavior > was to silently fail if, while setting the brightness, the PWM could not This sounds wrong. > be set up. This seemed rather confusing to me (I encountered this while > I was initially working on the tablet, I added a "pwm" property instead > of "pwms" and was wondering why the backlight didn't work...) > > Of course, that could be fixed by adding error detection in the > brightness set function, but since I was already working on it, it made > more sense to me for the PWM to be set up during the probing process, > given that this way we could 1. warn about errors early, and 2. catch > deferred probes and defer the backlight's probe if we're still waiting > for the PWM. That's why it's done the way it is in this patch. > > If this is undesired behavior, let me know and I'll submit another patch > to revert it. Best regards Uwe
diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c index 81012bf29baf..21eb4943ed56 100644 --- a/drivers/video/backlight/lp855x_bl.c +++ b/drivers/video/backlight/lp855x_bl.c @@ -218,23 +218,10 @@ static int lp855x_configure(struct lp855x *lp) static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br) { - struct pwm_device *pwm; struct pwm_state state; - /* request pwm device with the consumer name */ - if (!lp->pwm) { - pwm = devm_pwm_get(lp->dev, lp->chipname); - if (IS_ERR(pwm)) - return; - - lp->pwm = pwm; - - pwm_init_state(lp->pwm, &state); - } else { - pwm_get_state(lp->pwm, &state); - } + pwm_get_state(lp->pwm, &state); - state.period = lp->pdata->period_ns; state.duty_cycle = div_u64(br * state.period, max_br); state.enabled = state.duty_cycle; @@ -339,6 +326,7 @@ static int lp855x_parse_dt(struct lp855x *lp) of_property_read_string(node, "bl-name", &pdata->name); of_property_read_u8(node, "dev-ctrl", &pdata->device_control); of_property_read_u8(node, "init-brt", &pdata->initial_brightness); + /* Deprecated, specify period in pwms property instead */ of_property_read_u32(node, "pwm-period", &pdata->period_ns); /* Fill ROM platform data if defined */ @@ -399,6 +387,7 @@ static int lp855x_probe(struct i2c_client *cl) const struct i2c_device_id *id = i2c_client_get_device_id(cl); const struct acpi_device_id *acpi_id = NULL; struct device *dev = &cl->dev; + struct pwm_state pwmstate; struct lp855x *lp; int ret; @@ -457,11 +446,6 @@ static int lp855x_probe(struct i2c_client *cl) } } - if (lp->pdata->period_ns > 0) - lp->mode = PWM_BASED; - else - lp->mode = REGISTER_BASED; - lp->supply = devm_regulator_get(dev, "power"); if (IS_ERR(lp->supply)) { if (PTR_ERR(lp->supply) == -EPROBE_DEFER) @@ -472,11 +456,31 @@ static int lp855x_probe(struct i2c_client *cl) lp->enable = devm_regulator_get_optional(dev, "enable"); if (IS_ERR(lp->enable)) { ret = PTR_ERR(lp->enable); - if (ret == -ENODEV) { + if (ret == -ENODEV) lp->enable = NULL; - } else { + else return dev_err_probe(dev, ret, "getting enable regulator\n"); - } + } + + lp->pwm = devm_pwm_get(lp->dev, lp->chipname); + if (IS_ERR(lp->pwm)) { + ret = PTR_ERR(lp->pwm); + if (ret == -ENODEV || ret == -EINVAL) + lp->pwm = NULL; + else + return dev_err_probe(dev, ret, "getting PWM\n"); + + lp->mode = REGISTER_BASED; + dev_dbg(dev, "mode: register based\n"); + } else { + pwm_init_state(lp->pwm, &pwmstate); + /* Legacy platform data compatibility */ + if (lp->pdata->period_ns > 0) + pwmstate.period = lp->pdata->period_ns; + pwm_apply_state(lp->pwm, &pwmstate); + + lp->mode = PWM_BASED; + dev_dbg(dev, "mode: PWM based\n"); } if (lp->supply) {
Also deprecate the pwm-period DT property, as it is now redundant (pwms property already contains period value). Signed-off-by: Artur Weber <aweber.kernel@gmail.com> --- drivers/video/backlight/lp855x_bl.c | 48 ++++++++++++++++------------- 1 file changed, 26 insertions(+), 22 deletions(-)