Re: [PATCH v13 2/2] Add PWM fan controller driver for LGM SoC

["Tanwar, Rahul" <rahul.tanwar@linux.intel.com>]

Hi Uwe,

Thanks for review & feedback.

On 24/9/2020 2:55 pm, Uwe Kleine-König wrote:
> Hello,
>
> (hhm Thierry already announced to have taken this patch, so my review is
> late.)
>
> On Tue, Sep 15, 2020 at 04:23:37PM +0800, Rahul Tanwar wrote:
>> Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
>> This PWM controller does not have any other consumer, it is a
>> dedicated PWM controller for fan attached to the system. Add
>> driver for this PWM fan controller.
>>
>> Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
>> ---
>>  drivers/pwm/Kconfig         |  11 ++
>>  drivers/pwm/Makefile        |   1 +
>>  drivers/pwm/pwm-intel-lgm.c | 246 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 258 insertions(+)
>>  create mode 100644 drivers/pwm/pwm-intel-lgm.c
>>
>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>> index 7dbcf6973d33..4949c51fe90b 100644
>> --- a/drivers/pwm/Kconfig
>> +++ b/drivers/pwm/Kconfig
>> @@ -232,6 +232,17 @@ config PWM_IMX_TPM
>>  	  To compile this driver as a module, choose M here: the module
>>  	  will be called pwm-imx-tpm.
>>  
>> +config PWM_INTEL_LGM
>> +	tristate "Intel LGM PWM support"
>> +	depends on HAS_IOMEM
>> +	depends on (OF && X86) || COMPILE_TEST
>> +	select REGMAP_MMIO
>> +	help
>> +	  Generic PWM fan controller driver for LGM SoC.
>> +
>> +	  To compile this driver as a module, choose M here: the module
>> +	  will be called pwm-intel-lgm.
>> +
>>  config PWM_IQS620A
>>  	tristate "Azoteq IQS620A PWM support"
>>  	depends on MFD_IQS62X || COMPILE_TEST
>> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
>> index 2c2ba0a03557..e9431b151694 100644
>> --- a/drivers/pwm/Makefile
>> +++ b/drivers/pwm/Makefile
>> @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
>>  obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
>>  obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
>>  obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
>> +obj-$(CONFIG_PWM_INTEL_LGM)	+= pwm-intel-lgm.o
>>  obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
>>  obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
>>  obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
>> diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
>> new file mode 100644
>> index 000000000000..ea3df75a5971
>> --- /dev/null
>> +++ b/drivers/pwm/pwm-intel-lgm.c
>> @@ -0,0 +1,246 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2020 Intel Corporation.
>> + *
>> + * Limitations:
>> + * - The hardware supports fixed period which is dependent on 2/3 or 4
>> + *   wire fan mode.
> The driver now hardcodes 2-wire mode. IMHO that is worth mentioning.

Will update.

>> +static void lgm_clk_disable(void *data)
>> +{
>> +	struct lgm_pwm_chip *pc = data;
>> +
>> +	clk_disable_unprepare(pc->clk);
>> +}
>> +
>> +static int lgm_clk_enable(struct device *dev, struct lgm_pwm_chip *pc)
>> +{
>> +	int ret;
>> +
>> +	ret = clk_prepare_enable(pc->clk);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return devm_add_action_or_reset(dev, lgm_clk_disable, pc);
>> +}
> My first reflex here was to point out that lgm_clk_disable() isn't the
> counter part to lgm_clk_enable() and so lgm_clk_disable() needs
> adaption. On a second look this is correct and so I think the function
> names are wrong. The usual naming would be to use _release instead of
> _disable. Having said that the enable function could be named
> devm_clk_enable and live in drivers/clk/clk-devres.c. (Or
> devm_clk_get_enabled()?)


Will change function name from _disable to _release. But i think addition
of a generic devm_clk_enable in drivers/clk/clk-devres.c can be taken as
a separate task in a future patch (not clubbed with this driver)..


>> +static void lgm_reset_control_assert(void *data)
>> +{
>> +	struct lgm_pwm_chip *pc = data;
>> +
>> +	reset_control_assert(pc->rst);
>> +}
>> +
>> +static int lgm_reset_control_deassert(struct device *dev, struct lgm_pwm_chip *pc)
>> +{
>> +	int ret;
>> +
>> +	ret = reset_control_deassert(pc->rst);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return devm_add_action_or_reset(dev, lgm_reset_control_assert, pc);
>> +}
> A similar comment applies here.
>
>> +static int lgm_pwm_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct lgm_pwm_chip *pc;
>> +	void __iomem *io_base;
>> +	int ret;
>> +
>> +	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
>> +	if (!pc)
>> +		return -ENOMEM;
>> +
>> +	platform_set_drvdata(pdev, pc);
>> +
>> +	io_base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(io_base))
>> +		return PTR_ERR(io_base);
>> +
>> +	pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
>> +	if (IS_ERR(pc->regmap))
>> +		return dev_err_probe(dev, PTR_ERR(pc->regmap),
>> +				     "failed to init register map\n");
>> +
>> +	pc->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(pc->clk))
>> +		return dev_err_probe(dev, PTR_ERR(pc->clk), "failed to get clock\n");
>> +
>> +	ret = lgm_clk_enable(dev, pc);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable clock\n");
> You used dev_err_probe four times for six error paths. I wonder why you
> didn't use it here (and below for a failing pwmchip_add()).

Well noted, will update.

>> +		return ret;
>> +	}
>> +
>> +	pc->rst = devm_reset_control_get_exclusive(dev, NULL);
>> +	if (IS_ERR(pc->rst))
>> +		return dev_err_probe(dev, PTR_ERR(pc->rst),
>> +				     "failed to get reset control\n");
>> +
>> +	ret = lgm_reset_control_deassert(dev, pc);
>> +	if (ret)
>> +		return dev_err_probe(dev, ret, "cannot deassert reset control\n");
> After lgm_reset_control_deassert is called pc->rst is unused. So there
> is no need to have this member in struct lgm_pwm_chip. The same applies
> to ->clk. (You have to pass rst (or clk) to devm_add_action_or_reset for
> that to work. Looks like a nice idea anyhow.)

Agreed, will update.

>> +	pc->chip.dev = dev;
>> +	pc->chip.ops = &lgm_pwm_ops;
>> +	pc->chip.npwm = 1;
> pc->chip.base should probably be set to -1.

Got it, will update. Thanks.

Regards,
Rahul

> Best regards
> Uwe
>