[PATCH v2] pwm: pxa: add device tree support to pwm driver
Mike Dunn
mikedunn at newsguy.com
Sun Sep 8 15:40:18 EDT 2013
This patch adds device tree support to the pxa's pwm driver. Only an OF match
table is added; nothing needs to be extracted from the device tree node. The
existing platform_device id table is reused for the match table data. Support
for inverted polarity is also added.
Tested on a Palm Treo 680 (both platform data and DT cases).
Signed-off-by: Mike Dunn <mikedunn at newsguy.com>
---
Changle log:
v2:
- of_match_table contains only the "pxa250-pwm" compatible string; require one
device instance per pwm
- add Documentation/devicetree/bindings/pwm/pxa-pwm.txt
- add support for polarity flag in DT and implement set_polarity() method
(the treo 680 inverts the signal between pwm out and backlight)
- return -EINVAL instead of -ENODEV if platform data or DT node not found
- output dev_info string if platform data missing
- expanded CC list of patch
Documentation/devicetree/bindings/pwm/pxa-pwm.txt | 33 +++++++++++++
arch/arm/boot/dts/pxa27x.dtsi | 24 ++++++++++
drivers/pwm/pwm-pxa.c | 57 +++++++++++++++++++++++
3 files changed, 114 insertions(+)
create mode 100644 Documentation/devicetree/bindings/pwm/pxa-pwm.txt
diff --git a/Documentation/devicetree/bindings/pwm/pxa-pwm.txt b/Documentation/devicetree/bindings/pwm/pxa-pwm.txt
new file mode 100644
index 0000000..7b09bfa
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pxa-pwm.txt
@@ -0,0 +1,33 @@
+Marvell pwm controller
+
+Required properties:
+- compatible:
+ for pxa25x, pxa27x, pxa168, pxa910: must be compatible = "marvell,pxa250-pwm";
+- reg: physical base address and length of the registers used by the pwm channel
+ NB: One device instance must be created for each pwm that is used, so the
+ length covers only the register window for one pwm output, not that of the
+ entire pwm controller. Currently length is 0x10 for all supported devices.
+- #pwm-cells: should be 3.
+ cell 1: the per-chip index of the PWM to use,
+ cell 2: the period in nanoseconds,
+ cell 3: flags; set bit 0 to specify inverse polarity. The pwm controller
+ does not implement reverse polarity, but some boards may pass the pwm output
+ through an external inverter, which can cause problems if a client device
+ assumes that an increase in the duty cycle results in an increase in output
+ power. The pwm-backlight is an example of such a client.
+
+Example pwm device node:
+
+pwm0: pwm at 40b00000 {
+ compatible = "marvell,pxa250-pwm";
+ reg = <0x40b00000 0x10>;
+ #pwm-cells = <3>;
+};
+
+Example pwm client node:
+
+backlight {
+ compatible = "pwm-backlight";
+ pwms = <&pwm0 0 5000000 1>; /* pwm output is inverted */
+ ...
+}
diff --git a/arch/arm/boot/dts/pxa27x.dtsi b/arch/arm/boot/dts/pxa27x.dtsi
index d7c5d72..a12fe8e 100644
--- a/arch/arm/boot/dts/pxa27x.dtsi
+++ b/arch/arm/boot/dts/pxa27x.dtsi
@@ -10,5 +10,29 @@
marvell,intc-priority;
marvell,intc-nr-irqs = <34>;
};
+
+ pwm0: pwm at 40b00000 {
+ compatible = "marvell,pxa250-pwm";
+ reg = <0x40b00000 0x10>;
+ #pwm-cells = <3>;
+ };
+
+ pwm1: pwm at 40b00010 {
+ compatible = "marvell,pxa250-pwm";
+ reg = <0x40b00010 0x10>;
+ #pwm-cells = <3>;
+ };
+
+ pwm2: pwm at 40c00000 {
+ compatible = "marvell,pxa250-pwm";
+ reg = <0x40c00000 0x10>;
+ #pwm-cells = <3>;
+ };
+
+ pwm3: pwm at 40c00010 {
+ compatible = "marvell,pxa250-pwm";
+ reg = <0x40c00010 0x10>;
+ #pwm-cells = <3>;
+ };
};
};
diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
index a4d2164..33e6a7d 100644
--- a/drivers/pwm/pwm-pxa.c
+++ b/drivers/pwm/pwm-pxa.c
@@ -19,6 +19,7 @@
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pwm.h>
+#include <linux/of_device.h>
#include <asm/div64.h>
@@ -48,6 +49,7 @@ struct pxa_pwm_chip {
struct clk *clk;
void __iomem *mmio_base;
+ enum pwm_polarity polarity;
};
static inline struct pxa_pwm_chip *to_pxa_pwm_chip(struct pwm_chip *chip)
@@ -88,6 +90,15 @@ static int pxa_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
else
dc = (pv + 1) * duty_ns / period_ns;
+ if (pc->polarity == PWM_POLARITY_INVERSED) {
+ if (dc & PWMDCR_FD)
+ dc = 0; /* continuously low */
+ else if (dc == 0)
+ dc = PWMDCR_FD; /* continuously high */
+ else
+ dc = 1023 - dc; /* complement duty cycle */
+ }
+
/* NOTE: the clock to PWM has to be enabled first
* before writing to the registers
*/
@@ -117,13 +128,51 @@ static void pxa_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
clk_disable_unprepare(pc->clk);
}
+static int pxa_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+ enum pwm_polarity polarity)
+{
+ struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
+ pc->polarity = polarity;
+ return 0;
+}
+
static struct pwm_ops pxa_pwm_ops = {
.config = pxa_pwm_config,
.enable = pxa_pwm_enable,
.disable = pxa_pwm_disable,
+ .set_polarity = pxa_pwm_set_polarity,
.owner = THIS_MODULE,
};
+#ifdef CONFIG_OF
+/*
+ * Device tree users should create one device instance for each pwm channel.
+ * Hence we dispense with the HAS_SECONDARY_PWM and "tell" the original driver
+ * code that this is a single channel pxa25x-pwm.
+ */
+static struct of_device_id pwm_of_match[] = {
+ { .compatible = "marvell,pxa250-pwm", .data = &pwm_id_table[0]},
+ { }
+};
+MODULE_DEVICE_TABLE(of, pwm_of_match);
+
+static const struct platform_device_id *pxa_pwm_get_id_dt(struct device *dev)
+{
+ const struct of_device_id *pwm_pxa_devid =
+ of_match_device(pwm_of_match, dev);
+ if (pwm_pxa_devid)
+ return (const struct platform_device_id *)pwm_pxa_devid->data;
+ else
+ return NULL;
+}
+#else /* !CONFIG_OF */
+static const struct platform_device_id *pxa_pwm_get_id_dt(struct device *dev)
+{
+ dev_info(dev, "missing platform data\n");
+ return NULL;
+}
+#endif
+
static int pwm_probe(struct platform_device *pdev)
{
const struct platform_device_id *id = platform_get_device_id(pdev);
@@ -131,6 +180,11 @@ static int pwm_probe(struct platform_device *pdev)
struct resource *r;
int ret = 0;
+ if (id == NULL) /* using device tree */
+ id = pxa_pwm_get_id_dt(&pdev->dev);
+ if (id == NULL)
+ return -EINVAL;
+
pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
if (pwm == NULL) {
dev_err(&pdev->dev, "failed to allocate memory\n");
@@ -145,6 +199,8 @@ static int pwm_probe(struct platform_device *pdev)
pwm->chip.ops = &pxa_pwm_ops;
pwm->chip.base = -1;
pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;
+ pwm->chip.of_xlate = of_pwm_xlate_with_flags;
+ pwm->chip.of_pwm_n_cells = 3;
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
@@ -176,6 +232,7 @@ static struct platform_driver pwm_driver = {
.driver = {
.name = "pxa25x-pwm",
.owner = THIS_MODULE,
+ .of_match_table = of_match_ptr(pwm_of_match),
},
.probe = pwm_probe,
.remove = pwm_remove,
--
1.8.1.5
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