Hi Stefan, > Hi Stefan, > > > On 2016-10-12 15:15, Lukasz Majewski wrote: > > > Hi Stefan, > > > > > >> On 2016-10-07 08:11, Bhuvanchandra DV wrote: > > >> > From: Lothar Wassmann > > >> > > > >> > The i.MX pwm unit on i.MX27 and newer SoCs provides a > > >> > configurable output polarity. This patch adds support to > > >> > utilize this feature where available. > > >> > > > >> > Signed-off-by: Lothar Waßmann > > >> > Signed-off-by: Lukasz Majewski > > >> > Signed-off-by: Bhuvanchandra DV > > >> > Acked-by: Shawn Guo > > >> > Reviewed-by: Sascha Hauer > > >> > --- > > >> > Documentation/devicetree/bindings/pwm/imx-pwm.txt | 6 +-- > > >> > drivers/pwm/pwm-imx.c | 51 > > >> > +++++++++++++++++++++-- 2 files changed, 51 insertions(+), 6 > > >> > deletions(-) > > >> > > > >> > diff --git a/Documentation/devicetree/bindings/pwm/imx-pwm.txt > > >> > b/Documentation/devicetree/bindings/pwm/imx-pwm.txt > > >> > index e00c2e9..c61bdf8 100644 > > >> > --- a/Documentation/devicetree/bindings/pwm/imx-pwm.txt > > >> > +++ b/Documentation/devicetree/bindings/pwm/imx-pwm.txt > > >> > @@ -6,8 +6,8 @@ Required properties: > > >> > - "fsl,imx1-pwm" for PWM compatible with the one integrated > > >> > on i.MX1 > > >> > - "fsl,imx27-pwm" for PWM compatible with the one integrated > > >> > on i.MX27 > > >> > - reg: physical base address and length of the controller's > > >> > registers -- #pwm-cells: should be 2. See pwm.txt in this > > >> > directory for a description of > > >> > - the cells format. > > >> > +- #pwm-cells: 2 for i.MX1 and 3 for i.MX27 and newer SoCs. See > > >> > pwm.txt > > >> > + in this directory for a description of the cells format. > > >> > - clocks : Clock specifiers for both ipg and per clocks. > > >> > - clock-names : Clock names should include both "ipg" and > > >> > "per" See the clock consumer binding, > > >> > @@ -17,7 +17,7 @@ See the clock consumer binding, > > >> > Example: > > >> > > > >> > pwm1: pwm@53fb4000 { > > >> > - #pwm-cells = <2>; > > >> > + #pwm-cells = <3>; > > >> > compatible = "fsl,imx53-pwm", "fsl,imx27-pwm"; > > >> > reg = <0x53fb4000 0x4000>; > > >> > clocks = <&clks IMX5_CLK_PWM1_IPG_GATE>, > > >> > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c > > >> > index d600fd5..c37d223 100644 > > >> > --- a/drivers/pwm/pwm-imx.c > > >> > +++ b/drivers/pwm/pwm-imx.c > > >> > @@ -38,6 +38,7 @@ > > >> > #define MX3_PWMCR_DOZEEN (1 << 24) > > >> > #define MX3_PWMCR_WAITEN (1 << 23) > > >> > #define MX3_PWMCR_DBGEN (1 << 22) > > >> > +#define MX3_PWMCR_POUTC (1 << 18) > > >> > #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16) > > >> > #define MX3_PWMCR_CLKSRC_IPG (1 << 16) > > >> > #define MX3_PWMCR_SWR (1 << 3) > > >> > @@ -180,6 +181,9 @@ static int imx_pwm_config_v2(struct > > >> > pwm_chip *chip, if (enable) > > >> > cr |= MX3_PWMCR_EN; > > >> > > > >> > + if (pwm->args.polarity == PWM_POLARITY_INVERSED) > > >> > + cr |= MX3_PWMCR_POUTC; > > >> > + > > >> > > >> This seems wrong to me, the config callback is meant for > > >> period/duty cycle only. Unfortunately, it also resets the PWM IP block and setups it again (by writing to PWMCR register). In that function we setup for example MX3_PWMCR_DOZEEN and MX3_PWMCR_DBGEN. Why cannot we setup polarity as well? I've double checked the backlight and pwm code flow. Please find following snippet: [ 0.135545] ######### imx_pwm_probe [ 0.135581] PWM supports output inversion [ 0.136864] ######### pwm_backlight_probe [ 0.136913] backlight supply power not found, using dummy regulator [ 0.136984] ######### imx_pwm_set_polarity 1 [ 0.136995] imx_pwm_set_polarity: polarity set to inverted cr: 0x40000 0xf08f8000 [ 0.137005] #########0 imx_pwm_config_v2 cr: 0x40000 [ 0.137683] #########1 imx_pwm_config_v2 cr: 0x0 0xf08f8000 [ 0.137693] #########2 imx_pwm_config_v2 cr: 0x1c20050 [ 0.137702] #########3 imx_pwm_config_v2 cr: 0x1c20050 0xf08f8000 [ 0.137711] @@@@@@@@@@ pwm_apply_state Here the pwm_backlight_probe calls set_polarity callback available in pwm - the polarity is set (the 0x40000 value). The above operation is performed in pwm_apply_state (@ drivers/pwm/core.c). In the same function, latter we call the pwm->chip->ops->config(), which is the pointer to config_v2. Since the PWM is not yet enabled, this function performs SW reset and PWM inversion setting is cleared. Possible solutions: 1. Leave the original patch from Bhuvanchandra as it was (I'm for this option) 2. Enable early PWM (in core, or in bl driver) so the config_v2 is not calling SW reset on the PWM. (but this solutions seems _really_ bad to me) 3. Perform defer probe of pwm backlight driver (pwm_bl.c) until the pwm is fully configured (it might be a bit tricky). Best regards, Łukasz Majewski > > > > > > If it is meant only for that, then the polarity should be removed > > > from it. > > > > > > However after very quick testing, at least on my setup, it turns > > > out that removing this lines causes polarity to _not_ being set > > > (and the polarity is not inverted). > > > > > > I will investigate this further on my setup and hopefully sent > > > proper patch. > > > > > >> The set_polarity callback should get called in case a > > >> different polarity is requested. > > > > > > On my setup the pwm2 is set from DT and pwm_backlight_probe() > > > calls pwm_apply_args(), so everything should work. However, as I > > > mentioned above there still is some problem with inversion > > > setting. > > > > > >> > > >> > > >> > writel(cr, imx->mmio_base + MX3_PWMCR); > > >> > > > >> > return 0; > > >> > @@ -240,27 +244,62 @@ static void imx_pwm_disable(struct > > >> > pwm_chip *chip, struct pwm_device *pwm) > > >> > clk_disable_unprepare(imx->clk_per); > > >> > } > > >> > > > >> > -static struct pwm_ops imx_pwm_ops = { > > >> > +static int imx_pwm_set_polarity(struct pwm_chip *chip, struct > > >> > pwm_device *pwm, > > >> > + enum pwm_polarity polarity) > > >> > +{ > > >> > + struct imx_chip *imx = to_imx_chip(chip); > > >> > + u32 val; > > >> > + > > >> > + if (polarity == pwm->args.polarity) > > >> > + return 0; > > >> > > >> I don't think that this is right. Today, pwm_apply_args (in > > >> include/linux/pwm.h) copies the polarity from args to > > >> state.polarity, which is then passed as polarity argument to this > > >> function. So this will always return 0 afaict. > > > > > > Yes, I've overlooked it (that the state is copied). > > > > > > It can be dropped. > > > > Did you do the above test with that line dropped? > > Yes. The above code has been also removed. > > Best regards, > Łukasz Majewski > > > > > > > > >> > > >> I would just drop that. > > >> > > >> There is probably one little problem in the current state of > > >> affairs: If the bootloader makes use of a PWM channel with > > >> inverted state, then the kernel would not know about that and > > >> currently assume a wrong initial state... I guess at one point in > > >> time we should implement the state retrieval callback and move to > > >> the new atomic PWM API, which would mean to implement apply > > >> callback. > > > > > > Are there any patches on the horizon? > > > > > > > Not that I know of... > > > > -- > > Stefan > > > > >> > > >> -- > > >> Stefan > > >> > > >> > > >> > + > > >> > + val = readl(imx->mmio_base + MX3_PWMCR); > > >> > + > > >> > + if (polarity == PWM_POLARITY_INVERSED) > > >> > + val |= MX3_PWMCR_POUTC; > > >> > + else > > >> > + val &= ~MX3_PWMCR_POUTC; > > >> > + > > >> > + writel(val, imx->mmio_base + MX3_PWMCR); > > >> > + > > >> > + dev_dbg(imx->chip.dev, "%s: polarity set to %s\n", > > >> > __func__, > > >> > + polarity == PWM_POLARITY_INVERSED ? > > >> > "inverted" : "normal"); + > > >> > + return 0; > > >> > +} > > >> > + > > >> > +static struct pwm_ops imx_pwm_ops_v1 = { > > >> > .enable = imx_pwm_enable, > > >> > .disable = imx_pwm_disable, > > >> > .config = imx_pwm_config, > > >> > .owner = THIS_MODULE, > > >> > }; > > >> > > > >> > +static struct pwm_ops imx_pwm_ops_v2 = { > > >> > + .enable = imx_pwm_enable, > > >> > + .disable = imx_pwm_disable, > > >> > + .set_polarity = imx_pwm_set_polarity, > > >> > + .config = imx_pwm_config, > > >> > + .owner = THIS_MODULE, > > >> > +}; > > >> > + > > >> > struct imx_pwm_data { > > >> > int (*config)(struct pwm_chip *chip, > > >> > struct pwm_device *pwm, int duty_ns, int > > >> > period_ns); void (*set_enable)(struct pwm_chip *chip, bool > > >> > enable); > > >> > + struct pwm_ops *pwm_ops; > > >> > }; > > >> > > > >> > static struct imx_pwm_data imx_pwm_data_v1 = { > > >> > .config = imx_pwm_config_v1, > > >> > .set_enable = imx_pwm_set_enable_v1, > > >> > + .pwm_ops = &imx_pwm_ops_v1, > > >> > }; > > >> > > > >> > static struct imx_pwm_data imx_pwm_data_v2 = { > > >> > .config = imx_pwm_config_v2, > > >> > .set_enable = imx_pwm_set_enable_v2, > > >> > + .pwm_ops = &imx_pwm_ops_v2, > > >> > }; > > >> > > > >> > static const struct of_device_id imx_pwm_dt_ids[] = { > > >> > @@ -282,6 +321,8 @@ static int imx_pwm_probe(struct > > >> > platform_device *pdev) if (!of_id) > > >> > return -ENODEV; > > >> > > > >> > + data = of_id->data; > > >> > + > > >> > imx = devm_kzalloc(&pdev->dev, sizeof(*imx), > > >> > GFP_KERNEL); if (imx == NULL) > > >> > return -ENOMEM; > > >> > @@ -300,18 +341,22 @@ static int imx_pwm_probe(struct > > >> > platform_device *pdev) return PTR_ERR(imx->clk_ipg); > > >> > } > > >> > > > >> > - imx->chip.ops = &imx_pwm_ops; > > >> > + imx->chip.ops = data->pwm_ops; > > >> > imx->chip.dev = &pdev->dev; > > >> > imx->chip.base = -1; > > >> > imx->chip.npwm = 1; > > >> > imx->chip.can_sleep = true; > > >> > + if (data->pwm_ops->set_polarity) { > > >> > + dev_dbg(&pdev->dev, "PWM supports output > > >> > inversion\n"); > > >> > + imx->chip.of_xlate = of_pwm_xlate_with_flags; > > >> > + imx->chip.of_pwm_n_cells = 3; > > >> > + } > > >> > > > >> > r = platform_get_resource(pdev, IORESOURCE_MEM, 0); > > >> > imx->mmio_base = devm_ioremap_resource(&pdev->dev, r); > > >> > if (IS_ERR(imx->mmio_base)) > > >> > return PTR_ERR(imx->mmio_base); > > >> > > > >> > - data = of_id->data; > > >> > imx->config = data->config; > > >> > imx->set_enable = data->set_enable; > > >> > > > > > > Best regards, > > > > > > Łukasz Majewski >