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

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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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