Hi Peter,
On Thu, Jan 14, 2021 at 08:54:54AM +0800, Peter Chen wrote:
> On 21-01-13 12:18:35, Stephan Gerhold wrote:
> >
> > Also, on a completely different note I looked again at the chipidea USB
> > driver that produces this situation. To request the PHY (which ends up
> > in the circular device link) it does:
> >
> > /* Look for a generic PHY first */
> > ci->phy = devm_phy_get(dev->parent, "usb-phy");
> >
> > To me it doesn't really seem great to use the devm_* helpers on the
> > parent device either, so I will check if I can refactor this somehow.
> > Perhaps this situation can be prevented entirely.
> >
>
> You could try to get the PHY at parent driver
> (drivers/usb/chipidea/ci_hdrc_msm.c) to see the difference.
>
Unfortunately, I don't think this works in my case because I have an
ULPI PHY. It's not available until ret = ci_ulpi_init(ci); is called
from the ci_hdrc.0 platform device.
I tried the following diff yesterday. It prevents the circular device
link, therefore also the crash and even devm_* on the parent device:
diff --git a/drivers/usb/chipidea/core.c b/drivers/usb/chipidea/core.c
index aa40e510b806..79f556d0c93e 100644
--- a/drivers/usb/chipidea/core.c
+++ b/drivers/usb/chipidea/core.c
@@ -847,6 +847,8 @@ struct platform_device *ci_hdrc_add_device(struct device
*dev,
}
pdev->dev.parent = dev;
+ device_set_of_node_from_dev(&pdev->dev, dev);
+ pdev->driver_override = kstrdup("ci_hdrc", GFP_KERNEL);
ret = platform_device_add_resources(pdev, res, nres);
if (ret)
@@ -1027,7 +1029,7 @@ static int ci_hdrc_probe(struct platform_device *pdev)
ci->usb_phy = ci->platdata->usb_phy;
} else {
/* Look for a generic PHY first */
- ci->phy = devm_phy_get(dev->parent, "usb-phy");
+ ci->phy = devm_phy_get(dev, "usb-phy");
if (PTR_ERR(ci->phy) == -EPROBE_DEFER) {
ret = -EPROBE_DEFER;
Basically my idea was to share the of_node with the ci_hdrc.0 platform
device, so that it can request the PHY itself instead of going through
the parent.
It seems to work fine but I had to add pdev->driver_override to prevent
the ci_hdrc.0 device from probing using ci_hdrc_msm (since it considers
the "compatible" value on the of_node otherwise).
This is a bit weird (I think driver_override is mainly intended to be
written through sysfs, not from kernel code directly).
That is why I did not post this as a proper patch yet...
Thanks,
Stephan
