linux-kernel - Re: [PATCH V3 3/4] usb: dwc3: of-simple: Add support to get resets for the device

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Message-ID: <5a165379-1e33-1010-f502-8b4697150391@codeaurora.org>
Date:   Wed, 19 Apr 2017 17:32:47 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     swarren@...dotorg.org, balbi@...nel.org,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-usb@...r.kernel.org, thierry.reding@...il.com,
        gregkh@...uxfoundation.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH V3 3/4] usb: dwc3: of-simple: Add support to get resets
 for the device



On 04/19/2017 04:02 PM, Philipp Zabel wrote:
> On Tue, 2017-04-18 at 16:51 +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>
>> Cc: Philipp Zabel <p.zabel@...gutronix.de>
>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>> ---
>>   drivers/usb/dwc3/dwc3-of-simple.c | 36 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 36 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/dwc3-of-simple.c b/drivers/usb/dwc3/dwc3-of-simple.c
>> index fe414e7a9c78..9116df649f0b 100644
>> --- a/drivers/usb/dwc3/dwc3-of-simple.c
>> +++ b/drivers/usb/dwc3/dwc3-of-simple.c
>> @@ -29,13 +29,39 @@
>>   #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_array *resets;
>>   };
>>   
>> +static int dwc3_of_simple_reset_init(struct dwc3_of_simple *simple)
>> +{
>> +	struct device		*dev = simple->dev;
>> +	int			ret;
>> +
>> +	simple->resets = of_reset_control_array_get_exclusive(dev->of_node);
>> +	if (IS_ERR(simple->resets)) {
>> +		ret = PTR_ERR(simple->resets);
>> +		if (ret == -ENOENT)
>> +			/* not all controllers required resets */
>> +			return 0;
> If you use the of_reset_control_array_get_optional_exclusive variant,
> you can remove the three lines directly above.

No, it's a little tricky here.
of_reset_control_get_count() returns an error code, that we then return from
of_reset_control_array_get().

This is something that tegra/pmc driver required (return errorno in case 
count
of reset controls is zero.

So we handle that error separately here.

>
>> +		dev_err(dev, "failed to get device resets\n");
> It would be nice to print the error code here.

Sure.

>
>> +		return ret;
>> +	}
>> +
>> +	ret = reset_control_array_deassert(simple->resets);
>> +	if (ret) {
>> +		reset_control_array_put(simple->resets);
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   static int dwc3_of_simple_clk_init(struct dwc3_of_simple *simple, int count)
>>   {
>>   	struct device		*dev = simple->dev;
>> @@ -100,6 +126,10 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>>   	if (ret)
>>   		return ret;
>>   
>> +	ret = dwc3_of_simple_reset_init(simple);
>> +	if (ret)
>> +		return ret;
>> +
> I would just move the contents of dwc3_of_simple_reset_init here and add
> a goto error path at the end of dwc3_of_simple_clk_init to handle the
> reset control cleanup as needed.

Okay, i can restructure it.

>
>>   	ret = of_platform_populate(np, NULL, NULL, dev);
>>   	if (ret) {
>>   		for (i = 0; i < simple->num_clocks; i++) {
>> @@ -107,6 +137,9 @@ static int dwc3_of_simple_probe(struct platform_device *pdev)
>>   			clk_put(simple->clks[i]);
>>   		}
>>   
>> +		reset_control_array_assert(simple->resets);
>> +		reset_control_array_put(simple->resets);
>> +
>>   		return ret;
>>   	}
>>   
>> @@ -128,6 +161,9 @@ static int dwc3_of_simple_remove(struct platform_device *pdev)
>>   		clk_put(simple->clks[i]);
>>   	}
>>   
>> +	reset_control_array_assert(simple->resets);
>> +	reset_control_array_put(simple->resets);
>> +
> Must the reset be asserted before of_platform_depopulate?

Right, the order must be taken care of here. Will change this.

>
>>   	of_platform_depopulate(dev);
> Given the order above, I'd expect the reset cleanup here.

Sure.

>
>>   	pm_runtime_put_sync(dev);
> regards
> Philipp

Thanks for reviewing.

Best Regards
Vivek

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