Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi)
Signed-off-by: Bart Tanghe <[email protected]>
---
Changed in v7:
- clean up the shameful clk_enable error handling introduced in v6
- clean up the code nits
diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
new file mode 100644
index 0000000..d5162db
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
@@ -0,0 +1,27 @@
+BCM2835 PWM controller (Raspberry Pi controller)
+
+Required properties:
+- compatible: should be "brcm,bcm2835-pwm"
+- reg: physical base address and length of the controller's registers
+- clock: this clock defines the base clock frequency of the pwm
+hardware system, the period and the duty_cycle of the pwm signal is a
+multiple of the base period
+
+Examples:
+
+pwm@2020c000 {
+ compatible = "brcm,bcm2835-pwm";
+ reg = <0x2020c000 0x28>;
+ clocks = <&clk_pwm>;
+};
+
+clocks {
+ ....
+ clk_pwm: pwm {
+ compatible = "fixed-clock";
+ reg = <3>;
+ #clock-cells = <0>;
+ clock-frequency = <9200000>;
+ };
+ ....
+};
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 90c5c73..e533178 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -29,6 +29,15 @@ menuconfig PWM
if PWM
+config PWM_BCM2835
+ tristate "BCM2835 PWM support"
+ depends on ARCH_BCM2835
+ help
+ PWM framework driver for BCM2835 controller (Raspberry Pi)
+
+ To compile this driver as a module, choose M here: the module
+ will be called pwm-bcm2835
+
config PWM_BFIN
tristate "Blackfin PWM support"
depends on BFIN_GPTIMERS
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
new file mode 100644
index 0000000..99dc073
--- /dev/null
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -0,0 +1,202 @@
+/*
+ * Copyright 2014 Bart Tanghe <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define DUTY 0x14
+#define PERIOD 0x10
+#define CHANNEL 0x10
+
+#define PWM_ENABLE (1 << 0)
+#define PWM_POLARITY (1 << 4)
+
+#define PWM_CONTROL_MASK 0xff
+#define PWM_MODE 0x80 /* set timer in pwm mode */
+#define DEFAULT_PWM_MODE 0xff /* set timer in default mode */
+#define PWM_CONTROL_STRIDE 8
+#define MIN_PERIOD 108 /* 9.2Mhz max pwm clock */
+
+struct bcm2835_pwm {
+ struct pwm_chip chip;
+ struct device *dev;
+ int channel;
+ unsigned long scaler;
+ void __iomem *base;
+ struct clk *clk;
+};
+
+static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
+{
+ return container_of(chip, struct bcm2835_pwm, chip);
+}
+
+static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base);
+ value &= ~(PWM_CONTROL_MASK << (PWM_CONTROL_STRIDE * pwm->hwpwm));
+ value |= (PWM_MODE << (PWM_CONTROL_STRIDE * pwm->hwpwm));
+ writel(value, pc->base);
+ return 0;
+}
+
+static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base);
+ value &= (~DEFAULT_PWM_MODE << (PWM_CONTROL_STRIDE * pwm->hwpwm));
+ writel(value, pc->base);
+}
+
+static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ int duty_ns, int period_ns)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+
+ if (period_ns <= MIN_PERIOD) {
+ dev_err(pc->dev, "Period not supported\n");
+ return -EINVAL;
+ }
+ writel(duty_ns / pc->scaler, pc->base + DUTY + pwm->hwpwm * CHANNEL);
+ writel(period_ns / pc->scaler,
+ pc->base + PERIOD + pwm->hwpwm * CHANNEL);
+ return 0;
+}
+
+static int bcm2835_pwm_enable(struct pwm_chip *chip,
+ struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base);
+ value |= PWM_ENABLE << (PWM_CONTROL_STRIDE * pwm->hwpwm);
+ writel(value, pc->base);
+ return 0;
+}
+
+static void bcm2835_pwm_disable(struct pwm_chip *chip,
+ struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base);
+ value &= ~(PWM_ENABLE << (PWM_CONTROL_STRIDE * pwm->hwpwm));
+ writel(value, pc->base);
+}
+
+static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+ enum pwm_polarity polarity)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base);
+ if (polarity == PWM_POLARITY_NORMAL)
+ value &= ~(PWM_POLARITY << (PWM_CONTROL_STRIDE * pwm->hwpwm));
+ else if (polarity == PWM_POLARITY_INVERSED)
+ value |= PWM_POLARITY << (PWM_CONTROL_STRIDE * pwm->hwpwm);
+ writel(value, pc->base);
+ return 0;
+}
+
+static const struct pwm_ops bcm2835_pwm_ops = {
+ .request = bcm2835_pwm_request,
+ .free = bcm2835_pwm_free,
+ .config = bcm2835_pwm_config,
+ .enable = bcm2835_pwm_enable,
+ .disable = bcm2835_pwm_disable,
+ .set_polarity = bcm2835_set_polarity,
+ .owner = THIS_MODULE,
+};
+
+static int bcm2835_pwm_probe(struct platform_device *pdev)
+{
+ struct bcm2835_pwm *pwm;
+ int ret;
+ struct resource *r;
+ struct clk *clk;
+
+ pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+ if (!pwm)
+ return -ENOMEM;
+
+ pwm->dev = &pdev->dev;
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ pwm->base = devm_ioremap_resource(&pdev->dev, r);
+ if (IS_ERR(pwm->base))
+ return PTR_ERR(pwm->base);
+
+ clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(clk)) {
+ dev_err(&pdev->dev, "no clock found: %ld\n", PTR_ERR(clk));
+ return PTR_ERR(clk);
+ }
+
+ pwm->clk = clk;
+ ret = clk_prepare_enable(pwm->clk);
+ if (ret)
+ return ret;
+
+ pwm->scaler = NSEC_PER_SEC / clk_get_rate(clk);
+
+ pwm->chip.dev = &pdev->dev;
+ pwm->chip.ops = &bcm2835_pwm_ops;
+ pwm->chip.npwm = 2;
+
+ platform_set_drvdata(pdev, pwm);
+
+ ret = pwmchip_add(&pwm->chip);
+ if (ret < 0)
+ goto add_fail;
+
+ return 0;
+
+add_fail:
+ clk_disable_unprepare(pwm->clk);
+ return ret;
+}
+
+static int bcm2835_pwm_remove(struct platform_device *pdev)
+{
+ struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
+ clk_disable_unprepare(pc->clk);
+ return pwmchip_remove(&pc->chip);
+}
+
+static const struct of_device_id bcm2835_pwm_of_match[] = {
+ { .compatible = "brcm,bcm2835-pwm", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
+
+static struct platform_driver bcm2835_pwm_driver = {
+ .driver = {
+ .name = "bcm2835-pwm",
+ .of_match_table = bcm2835_pwm_of_match,
+ },
+ .probe = bcm2835_pwm_probe,
+ .remove = bcm2835_pwm_remove,
+};
+module_platform_driver(bcm2835_pwm_driver);
+
+MODULE_AUTHOR("Bart Tanghe <[email protected]");
+MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
+MODULE_LICENSE("GPL v2");
On Wed, Oct 08, 2014 at 12:14:32PM +0200, Bart Tanghe wrote:
> Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi)
>
> Signed-off-by: Bart Tanghe <[email protected]>
> ---
> Changed in v7:
> - clean up the shameful clk_enable error handling introduced in v6
> - clean up the code nits
>
> diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
> new file mode 100644
> index 0000000..d5162db
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
> @@ -0,0 +1,27 @@
> +BCM2835 PWM controller (Raspberry Pi controller)
> +
> +Required properties:
> +- compatible: should be "brcm,bcm2835-pwm"
> +- reg: physical base address and length of the controller's registers
> +- clock: this clock defines the base clock frequency of the pwm
> +hardware system, the period and the duty_cycle of the pwm signal is a
> +multiple of the base period
This needs to document the #pwm-cells property. I can fix that up when
applying, though.
Let's give Stephen and others a chance to give this another look.
Thierry
On 2014-10-08 14:19, Thierry Reding wrote:
> On Wed, Oct 08, 2014 at 12:14:32PM +0200, Bart Tanghe wrote:
>> Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi)
>>
>> Signed-off-by: Bart Tanghe <[email protected]>
>> ---
>> Changed in v7:
>> - clean up the shameful clk_enable error handling introduced in v6
>> - clean up the code nits
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> new file mode 100644
>> index 0000000..d5162db
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> @@ -0,0 +1,27 @@
>> +BCM2835 PWM controller (Raspberry Pi controller)
>> +
>> +Required properties:
>> +- compatible: should be "brcm,bcm2835-pwm"
>> +- reg: physical base address and length of the controller's registers
>> +- clock: this clock defines the base clock frequency of the pwm
>> +hardware system, the period and the duty_cycle of the pwm signal is a
>> +multiple of the base period
>
> This needs to document the #pwm-cells property. I can fix that up when
> applying, though.
>
> Let's give Stephen and others a chance to give this another look.
>
> Thierry
>
Perfect, thanks.
Bart
On 10/08/2014 03:14 AM, Bart Tanghe wrote:
> Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi)
Acked-by: Stephen Warren <[email protected]>
On Wed, Oct 08, 2014 at 12:14:32PM +0200, Bart Tanghe wrote:
[...]
> diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
[...]
> +static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> + u32 value;
> +
> + value = readl(pc->base);
> + value &= (~DEFAULT_PWM_MODE << (PWM_CONTROL_STRIDE * pwm->hwpwm));
While applying I noticed this oddity. Is this meant to be:
value &= ~(DEFAULT_PWM_MODE << (PWM_CONTROL_STRIDE * pwm->hwpwm));
? That would match what's in bcm2835_pwm_request(). If so, what's the
difference between DEFAULT_PWM_MODE and PWM_CONTROL_MASK? Is the value
of a channel's field 0xff or 0x00 in the default mode?
The above indicates that it would be 0x00, in which case it might be
better to just do...
value &= ~(PWM_CONTROL_MASK << (PWM_CONTROL_STRIDE * pwm->hwpwm));
... and get rid of DEFAULT_PWM_MODE.
No need to respin, I can fix this up when applying. Just let me know if
that's actually the right thing to do.
Thierry
On 2014-10-14 15:54, Thierry Reding wrote:
> The above indicates that it would be 0x00, in which case it might be
> better to just do...
>
> value &= ~(PWM_CONTROL_MASK << (PWM_CONTROL_STRIDE * pwm->hwpwm));
>
> ... and get rid of DEFAULT_PWM_MODE.
Indeed, this has to be 0x00. PWM_CONTROL_MASK and DEFAULT_PWM_MODE are the same.
I've declared DEFAULT_PWM_MODE because they have another meaning but the values are the same.
You can definetly use
value &= ~(PWM_CONTROL_MASK << (PWM_CONTROL_STRIDE * pwm->hwpwm));
Bart