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Message-ID: <521330DD.2080308@atmel.com>
Date: Tue, 20 Aug 2013 17:03:25 +0800
From: Bo Shen <voice.shen@...el.com>
To: Nicolas Ferre <nicolas.ferre@...el.com>
CC: <linux-pwm@...r.kernel.org>,
Thierry Reding <thierry.reding@...il.com>,
<plagnioj@...osoft.com>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH] pwm: atmel-pwm: add pwm controller driver
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@...el.com>
>>
>> ---
>> 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@...34000 {
>> + 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@...el.com>
>> + *
>> + * 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
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