Re: [RFC PATCH] pwm: atmel-pwm: add pwm controller driver
From: Bo Shen
Date: Tue Aug 20 2013 - 05:03:42 EST
Hi Nicolas,
On 8/20/2013 16:33, Nicolas Ferre wrote:
On 19/08/2013 05:11, Bo Shen :
add atmel pwm controller driver based on PWM framework
this is basic function implementation of pwm controller
it can work with pwm based led and backlight
Signed-off-by: Bo Shen <voice.shen@xxxxxxxxx>
---
This patch is based on Linux v3.11 rc6
Tested on sama5d31ek and at91sam9m10g45ek board
---
.../devicetree/bindings/pwm/atmel-pwm.txt | 19 ++
drivers/pwm/Kconfig | 9 +
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-atmel.c | 327
++++++++++++++++++++
4 files changed, 356 insertions(+)
create mode 100644 Documentation/devicetree/bindings/pwm/atmel-pwm.txt
create mode 100644 drivers/pwm/pwm-atmel.c
diff --git a/Documentation/devicetree/bindings/pwm/atmel-pwm.txt
b/Documentation/devicetree/bindings/pwm/atmel-pwm.txt
new file mode 100644
index 0000000..127fcdb
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/atmel-pwm.txt
@@ -0,0 +1,19 @@
+Atmel PWM controller
+
+Required properties:
+ - compatible: should be one of:
+ - "atmel,at91sam9rl-pwm"
+ - "atmel,sama5-pwm"
No, the compatibility string should be: "atmel,sama5d3-pwm"
OK, I will change it in next version.
+ - reg: physical base address and length of the controller's registers
+ - #pwm-cells: Should be 3.
+ - The first cell specifies the per-chip index of the PWM to use
+ - The second cell is the period in nanoseconds
+ - The third cell is used to encode the polarity of PWM output
+
+Example:
+
+ pwm0: pwm@f8034000 {
+ compatible = "atmel,at91sam9rl-pwm";
+ reg = <0xf8034000 0x400>;
+ #pwm-cells = <3>;
+ };
Can you add an example of consumer: it would make the example much more
understandable.
I will add an example of consumer.
[...]
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
new file mode 100644
index 0000000..b83d68e
--- /dev/null
+++ b/drivers/pwm/pwm-atmel.c
@@ -0,0 +1,327 @@
+/*
+ * Driver for Atmel Pulse Width Modulation Controller
+ *
+ * Copyright (C) 2013 Atmel Semiconductor Technology Ltd.
use "Atmel Corporation" in copyright.
+ * Bo Shen <voice.shen@xxxxxxxxx>
+ *
+ * GPL v2 or later
+ */
A general remark also pointed out by Thierry: please use more defined
constants in your code: it makes the code more readable and avoid this
black magic feeling when we read it.
Please help review v2.
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+
+#define PWM_MR 0x00
+#define PWM_ENA 0x04
+#define PWM_DIS 0x08
+#define PWM_SR 0x0C
+
+#define PWM_CMR 0x00
+
+/* The following register for PWM v1 */
+#define PWMv1_CDTY 0x04
+#define PWMv1_CPRD 0x08
+#define PWMv1_CUPD 0x10
+
+/* The following register for PWM v2 */
+#define PWMv2_CDTY 0x04
+#define PWMv2_CDTYUPD 0x08
+#define PWMv2_CPRD 0x0C
+#define PWMv2_CPRDUPD 0x10
+
+#define PWM_NUM 4
+
+struct atmel_pwm_chip {
+ struct pwm_chip chip;
+ struct clk *clk;
+ void __iomem *base;
+
+ void (*config)(struct atmel_pwm_chip *chip, struct pwm_device *pwm,
+ unsigned int dty, unsigned int prd);
+};
+
+#define to_atmel_pwm_chip(chip) container_of(chip, struct
atmel_pwm_chip, chip)
+
+static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip, int
offset)
+{
+ return readl(chip->base + offset);
+}
+
+static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip, int
offset,
+ u32 val)
+{
+ writel(val, chip->base + offset);
+}
+
+static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip, int
ch,
+ int offset)
+{
+ return readl(chip->base + 0x200 + ch * 0x20 + offset);
Maybe a constant for this 0x200 value...
OK. I will fix it in net version.
+}
+
+static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
int ch,
+ int offset, u32 val)
+{
+ writel(val, chip->base + 0x200 + ch * 0x20 + offset);
+}
+
+static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device
*pwm,
+ int duty_ns, int period_ns)
+{
+ struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
+ unsigned long long val, prd, dty;
+ unsigned long long div, clk_rate;
+ int ret, pres = 0;
+
+ clk_rate = clk_get_rate(atmel_pwm->clk);
+
+ while (1) {
Why not use a proper loop condition here instead of a frightening
while (true) loop? Is it really making the code less readable?
OK, I will try to use the proper loop condition here.
+ div = 1000000000;
use a constant or at least a comment for this initialization.
I will add comment in next version.
+ div *= 1 << pres;
+ val = clk_rate * period_ns;
+ prd = div_u64(val, div);
+ val = clk_rate * duty_ns;
+ dty = div_u64(val, div);
+
+ if (prd < 0x0001 || dty < 0x0)
+ return -EINVAL;
+
+ if (prd > 0xffff || dty > 0xffff) {
Yes, here define those constants please.
Please help review v2.
+ if (++pres > 0x10)
+ return -EINVAL;
+ continue;
+ }
+
+ break;
+ }
+
+ /* Enable clock */
+ ret = clk_prepare_enable(atmel_pwm->clk);
+ if (ret) {
+ pr_err("failed to enable pwm clock\n");
+ return ret;
+ }
+
+ atmel_pwm->config(atmel_pwm, pwm, dty, prd);
+
+ /* Check whether need to disable clock */
+ val = atmel_pwm_readl(atmel_pwm, PWM_SR);
+ if ((val & 0xf) == 0)
Ditto.
+ clk_disable_unprepare(atmel_pwm->clk);
+
+ return 0;
+}
+
Best Regards,
Bo Shen
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/