linux-kernel - Re: [PATCH 2/2] usb; dwc3: of-simple: Add support to get resets for the device

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Message-ID: <0f0ed385-30ea-7819-9533-f06b5e4eccfe@codeaurora.org>
Date:   Thu, 16 Mar 2017 11:04:20 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] usb; dwc3: of-simple: Add support to get resets for
 the device

Hi,


On 03/15/2017 04:15 PM, Philipp Zabel wrote:
> On Wed, 2017-02-22 at 10:54 +0530, Vivek Gautam wrote:
>> Add support to get a list of resets available for the device.
>> These resets must be kept de-asserted until the device is
>> in use.
>>
>> Cc: Felipe Balbi <balbi@...nel.org>
>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>> ---
>>
>> Based on torvald's master branch.
>>
>>   drivers/usb/dwc3/dwc3-of-simple.c | 49 +++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 49 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
>> index fe414e7a9c78..025de7342d28 100644
>> --- a/drivers/usb/dwc3/dwc3-of-simple.c
>> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
>> @@ -29,13 +29,52 @@
>>   #include <linux/of.h>
>>   #include <linux/of_platform.h>
>>   #include <linux/pm_runtime.h>
>> +#include <linux/reset.h>
>>   
>>   struct dwc3_of_simple {
>>   	struct device		*dev;
>>   	struct clk		**clks;
>>   	int			num_clocks;
>> +	struct reset_control	**resets;
>> +	int			num_resets;
>>   };
>>   
>> +static int dwc3_of_simple_reset_init(struct dwc3_of_simple *simple, int count)
>> +{
>> +	struct device		*dev = simple->dev;
>> +	int			i;
>> +
>> +	simple->num_resets = count;
>> +
>> +	if (!count)
>> +		return 0;
>> +
>> +	simple->resets = devm_kcalloc(dev, simple->num_resets,
>> +				sizeof(struct reset_control *), GFP_KERNEL);
>> +	if (!simple->resets)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < simple->num_resets; i++) {
>> +		struct reset_control *reset;
>> +		int ret;
>> +
>> +		reset = devm_reset_control_get_by_index(dev, i);
> Please use devm_reset_control_get_exclusive_by_index instead. See
> include/linux/reset.h for details.

Sure, will make use of *exclusive version of the api.

>
>> +		if (IS_ERR(reset))
>> +			return PTR_ERR(reset);
>> +
>> +		simple->resets[i] = reset;
>> +
>> +		ret = reset_control_deassert(reset);
>> +		if (ret) {
>> +			while (--i >= 0)
>> +				reset_control_assert(reset);
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
> This looks rather generic. Should we have a
> reset_control_get/assert/deassert_array functionality at the reset API
> level?

Yes, i think we should. Something on the lines of 'regulator_bulk_*' 
interface?

>
>>   static int dwc3_of_simple_clk_init(struct dwc3_of_simple *simple, int count)
>>   {
>>   	struct device		*dev = simple->dev;
>> @@ -100,6 +139,10 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>>   	if (ret)
>>   		return ret;
>>   
>> +	ret = dwc3_of_simple_reset_init(simple, of_reset_control_get_count(np));
>> +	if (ret)
>> +		return ret;
>> +
> Not a blocker, but it seems a bit inconsistent to count the reset
> controls via the device node (of_...), but then get them via the device
> (devm_reset_control_get_... instead of of_reset_control_get_...).

You are right, it looks inconsistent. I thought of using a resource
managed API. But now i think it doesn't make much sense.


Best Regards
Vivek

>
> regards
> Philipp
>

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