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

[Vivek Gautam]

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@xxxxxxxxxx>
> > Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> > ---
> >   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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