When inserting a USB device, examining hcd->rsrc_start can be
helpful in identifying which hcd is mounted, as the physical
address represented here is typically unique.

The following code snippet demonstrates this:
  struct usb_hcd *hcd = bus_to_hcd(udev->bus);
  unsigned long long usb_hcd_addr = (unsigned long long)hcd->rsrc_start;

However, this approach has limitations now. For USB hosts with an
MMIO interface, the effectiveness of this method is restricted to
USB 2.0.

Becase commit 3429e91a661e ("usb: host: xhci: add platform driver
support") assigned res->start to hcd->rsrc_start. But
shared_hcd->rsrc_start remains unassigned, which is also necessary
in certain scenarios.

Co-developed-by: Xu Rao <raoxu@uniontech.com>
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Signed-off-by: WangYuli <wangyuli@uniontech.com>
--
Changlog:
  v1 -> v2: Move code changes for commit e0fe986972f5 ("usb: host:
xhci-plat: prepare operation w/o shared hcd").
---
 drivers/usb/host/xhci-plat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index e6c9006bd568..457e839b9b53 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -329,6 +329,8 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
 		usb3_hcd->can_do_streams = 1;
 
 	if (xhci->shared_hcd) {
+		xhci->shared_hcd->rsrc_start = hcd->rsrc_start;
+		xhci->shared_hcd->rsrc_len = hcd->rsrc_len;
 		ret = usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
 		if (ret)
 			goto put_usb3_hcd;
-- 
2.45.2

On 4.1.2025 17.51, WangYuli wrote:
> When inserting a USB device, examining hcd->rsrc_start can be
> helpful in identifying which hcd is mounted, as the physical
> address represented here is typically unique.
> 
> The following code snippet demonstrates this:
>    struct usb_hcd *hcd = bus_to_hcd(udev->bus);
>    unsigned long long usb_hcd_addr = (unsigned long long)hcd->rsrc_start;
> 
> However, this approach has limitations now. For USB hosts with an
> MMIO interface, the effectiveness of this method is restricted to
> USB 2.0.
> 
> Becase commit 3429e91a661e ("usb: host: xhci: add platform driver
> support") assigned res->start to hcd->rsrc_start. But
> shared_hcd->rsrc_start remains unassigned, which is also necessary
> in certain scenarios.

Could you expand on those scenarios?

Is it possible those could be solved with something like:

unsigned long long usb_hcd_addr;
struct usb_hcd *hcd = bus_to_hcd(udev->bus);

if (!usb_hcd_is_primary_hcd(hcd))
	hcd = hcd->primary_hcd;
usb_hcd_addr = (unsigned long long)hcd->rsrc_start;

That should work for all hcds.

Thanks
Mathias

On Sat, Jan 04, 2025 at 11:51:11PM +0800, WangYuli wrote:
> When inserting a USB device, examining hcd->rsrc_start can be
> helpful in identifying which hcd is mounted, as the physical
> address represented here is typically unique.
> 
> The following code snippet demonstrates this:
>   struct usb_hcd *hcd = bus_to_hcd(udev->bus);
>   unsigned long long usb_hcd_addr = (unsigned long long)hcd->rsrc_start;
> 
> However, this approach has limitations now. For USB hosts with an
> MMIO interface, the effectiveness of this method is restricted to
> USB 2.0.
> 
> Becase commit 3429e91a661e ("usb: host: xhci: add platform driver
> support") assigned res->start to hcd->rsrc_start. But
> shared_hcd->rsrc_start remains unassigned, which is also necessary
> in certain scenarios.
> 
> Co-developed-by: Xu Rao <raoxu@uniontech.com>
> Signed-off-by: Xu Rao <raoxu@uniontech.com>
> Signed-off-by: WangYuli <wangyuli@uniontech.com>
> --
> Changlog:
>   v1 -> v2: Move code changes for commit e0fe986972f5 ("usb: host:
> xhci-plat: prepare operation w/o shared hcd").
> ---

What commit id does this fix?

thanks,

greg k-h

On 2025/1/7 18:36, Greg KH wrote:
> What commit id does this fix?

Hi Greg,

I'm not sure if this can be considered a bugfix for a specific commit.

Please see the commit message for more details.

If it is, then it does fix 3429e91a661e1 ("usb: host: xhci: add platform 
driver support").

> thanks,
>
> greg k-h
>
-- 
WangYuli