Re: [PATCH 3/3] usb: dwc2: prevent core phy initialisation

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Hi Greg,

On 12/8/22 16:53, Greg Kroah-Hartman wrote:
On Wed, Dec 07, 2022 at 02:19:18PM +0100, Quentin Schulz wrote:
From: Bin Yang <yangbin@xxxxxxxxxxxxxx>

The usb phys need to be controlled dynamically on some Rockchip SoCs.
So set the new HCD flag which prevents USB core from trying to manage
our phys.

Signed-off-by: Bin Yang <yangbin@xxxxxxxxxxxxxx>
Signed-off-by: Frank Wang <frank.wang@xxxxxxxxxxxxxx>
Signed-off-by: Quentin Schulz <quentin.schulz@xxxxxxxxxxxxxxxxxxxxx>
---
  drivers/usb/dwc2/hcd.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 657f1f659ffaf..757a66fa32fa8 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -5315,6 +5315,13 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg)
  	if (!IS_ERR_OR_NULL(hsotg->uphy))
  		otg_set_host(hsotg->uphy->otg, &hcd->self);
+ /*
+	 * do not manage the PHY state in the HCD core, instead let the driver
+	 * handle this (for example if the PHY can only be turned on after a
+	 * specific event)
+	 */
+	hcd->skip_phy_initialization = 1;

Wait, doesn't this mess with the phy logic for all other chips that use
this IP block?  Have you tested this on other systems?


I have not. I asked this in the cover-letter but I guess I should have made the patch series an RFC for this reason?

I'd like some verification first before taking this change as it seems
very specific-platform.


There's already some platform-specific callbacks for the driver (see
dwc2_set_rk_params in drivers/usb/dwc2/params.c) but this gets called too early, before hcd structure is actually allocated. So we either need to use some "proxy"/shadow variable in dwc2_core_params and then update it right after hcd gets allocated or have another platform-specific callback only for hcd (post-)initialization.

Nothing too fancy so shouldn't take too long to implement. Any preference? Something else?

Also on a side note, after further testing, USB peripheral mode in dual-role mode does not seem to be entirely fixed with this patch series, I still have occasional locks. But considering that it absolutely didn't work before, it is some kind of progress. There are also some issues related to USB host mode in dual-role mode but I saw those happening before the patch series too. I'll see what I can do, really frustrating to work with IPs for which there's no documentation :/

Cheers,
Quentin



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