linux-kernel - Re: [PATCH] pwm: add pwm driver for HiSilicon BVT SOCs

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Date:	Wed, 3 Aug 2016 14:32:52 +0800
From:	Jian Yuan <yuanjian12@...ilicon.com>
To:	Mark Rutland <mark.rutland@....com>
CC:	<thierry.reding@...il.com>, <robh+dt@...nel.org>,
	<xuejiancheng@...ilicon.com>, <kevin.lixu@...ilicon.com>,
	<jalen.hsu@...ilicon.com>, <linux-pwm@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pwm: add pwm driver for HiSilicon BVT SOCs



On 2016/8/1 20:43, Mark Rutland wrote:
> On Mon, Aug 01, 2016 at 09:42:08AM +0800, Jian Yuan wrote:
>> From: yuanjian <yuanjian12@...ilicon.com>
>>
>> Add pwm driver for HiSilicon BVT SOCs
>>
>> Reviewed-by: Jiancheng Xue <xuejiancheng@...ilicon.com>
>> Signed-off-by: Jian Yuan <yuanjian12@...ilicon.com>
>> ---
>>  .../devicetree/bindings/pwm/pwm-hibvt.txt          |  18 ++
>>  drivers/pwm/Kconfig                                |  10 +
>>  drivers/pwm/Makefile                               |   1 +
>>  drivers/pwm/pwm-hibvt.c                            | 272 +++++++++++++++++++++
>>  4 files changed, 301 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/pwm/pwm-hibvt.txt
>>  create mode 100644 drivers/pwm/pwm-hibvt.c
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-hibvt.txt b/Documentation/devicetree/bindings/pwm/pwm-hibvt.txt
>> new file mode 100644
>> index 0000000..4efd83e
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pwm/pwm-hibvt.txt
>> @@ -0,0 +1,18 @@
>> +Hisilicon PWM controller
>> +
>> +Required properties:
>> + - compatible: should be "hisilicon,hibvt-pwm" and one of the following:
>> +			"hisilicon,hi3516cv300-pwm".
> 
> I take it "hisilicon,hibvt-pwm" is the fallback entry.
> 
> It would be good to note that explicitly.
> 
I do not understand what the fallback entry means.

"hisilicon,hibvt-pwm" is a general compatible string, which is available for most HiSilicon BVT SOCs.
Howerver, "hisilicon,hi3516cv300-pwm" is specially for hi3516cv300.

Maybe I should note the compatible string as described above, right?

>> + - reg: physical base address and length of the controller's registers.
>> + - clocks: phandle and clock specifier of the PWM reference clock.
>> + - resets: offset address and offset bit for reset or unreset of the controller.
>> + - pwm-nums: pwm number of the controller.
> 
> This should be 'num-pwms'.
> 
> I assume this is the number of PWMs exposed by this controller. Is this
> not probeable, or dicoverable based on the compatible string?
> 
> How does this vary in practice?
> 
"pwm-nums" means the maximum number of PWMS that this controller can support, which is the hardware capability.
E.g.,HI3516CV300 PWM controller supports 4 PWM, while other chips support 8 PWM.

I agree that the PWM number is probeable based on the compatible string. I shall change it, thanks.

>> +
>> +Example:
>> +	pwm: pwm@...30000 {
>> +		compatible = "hisilicon,hibvt-pwm";
> 
> This is missing "hisilicon,hi3516cv300-pwm" as per the requirements of
> the binding.
> 
Ok, it's right. I'll fix it in next v2 patch.

>> +		reg = <0x12130000 0x10000>;
>> +		clocks = <&crg_ctrl HI3516CV300_PWM_CLK>;
>> +		resets = <&crg_ctrl 0x38 0>;
>> +		pwm-nums = <4>;
>> +	};
> 
> Thanks,
> Mark.
> 
> .
> 
Thanks,
Jian.