Hi Shimoda-san, On 08 August 2022 00:47 Yoshihiro Shimoda wrote: > > From: Phil Edworthy, Sent: Friday, August 5, 2022 10:10 PM > > > > Hi Geert, Yoshihiro, > > > > I'm a bit stuck with the usb3 drivers for RZ/V2M. > > > > The RZ/V2M USB3 is very similar to R-Car Gen3, the main difference being > > where the DRD registers are located and additional clocks, interrupts > > and resets exposed. The DRD registers are still part of the USBP address > > space, though they have been moved above the other USBP regs. > > > > There is however, one big difference. On RZ/V2M, you can only access the > > corresponding registers for whatever DRD mode has been set in the > > DRD_CON register, PERI_CON bit. That is to say, when PERI_CON=1 (periph > > mode), reading from a USBH register will cause an abort, and when > > PERI_CON=0 (host mode), reading from a USBP register will cause an > > abort. > > Thank you for asking me about this topic. I have a question: > Can the DRD register be accessed from both PERI_CON=1 and 0? Yes, that is correct. > > This makes role switching rather difficult in Linux as the usb host hub > > code does some work in a delayed work queue, after role switch. > > > > I am therefore advocating that users can only enable host or peripheral > > in DT, and role switching is not allowed. Is that reasonable? > > How can I ensure only one driver is enabled? > > > > This unfortunately opens up another problem... So that the USBH driver > > can set the DRD mode, it needs access to the USBP address space. Could > > that be just be additional reg entry in DT for this? > > > > I'm not sure how to go about this, any advice appreciated! > > If the DRD register can be accessed from both PERI_CON=1 and 0, > I have an idea how to handle this. > # However, I'm not sure whether this is a correct way or not though... > > My idea: > - Make a new role switch driver on drivers/usb/roles/ or drivers/mfd/. > - No describe any xHCI and USB3 UDC nodes in DT. > - Describe whole USB3 registers for the role device in DT. > (Or add sub nodes of xHCI and USB3 UDC into the role device.) > - The role switch driver handles the DRD register at first. Ok > And then, the driver adds xHCI or USB3 UDC device somehow. The role switch must shut down the USBH driver so that it no longer has the hub event work queue running. How can we do this? Thanks Phil
