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

[Vivek Gautam]

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@xxxxxxxxxx>
> > Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> > ---
> >
> > 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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