RE: [PATCH v12 1/3] misc: Add versal-usb2-ctrl-regs module

[Sai Pavan Boddu <saipava@xilinx.com>]

Hi Peter,

> -----Original Message-----
> From: Peter Maydell <peter.maydell@linaro.org>
> Sent: Monday, October 26, 2020 9:33 PM
> To: Sai Pavan Boddu <saipava@xilinx.com>
> Cc: Markus Armbruster <armbru@redhat.com>; Marc-André Lureau
> <marcandre.lureau@redhat.com>; Paolo Bonzini <pbonzini@redhat.com>;
> Gerd Hoffmann <kraxel@redhat.com>; Edgar Iglesias <edgari@xilinx.com>;
> Francisco Eduardo Iglesias <figlesia@xilinx.com>; QEMU Developers <qemu-
> devel@nongnu.org>; Alistair Francis <alistair.francis@wdc.com>; Eduardo
> Habkost <ehabkost@redhat.com>; Ying Fang <fangying1@huawei.com>;
> Philippe Mathieu-Daudé <philmd@redhat.com>; Vikram Garhwal
> <fnuv@xilinx.com>; Paul Zimmerman <pauldzim@gmail.com>; Sai Pavan Boddu
> <saipava@xilinx.com>
> Subject: Re: [PATCH v12 1/3] misc: Add versal-usb2-ctrl-regs module
> 
> On Thu, 22 Oct 2020 at 13:11, Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
> wrote:
> >
> > This module emulates control registers of versal usb2 controller, this
> > is added just to make guest happy. In general this module would
> > control the phy-reset signal from usb controller, data coherency of
> > the transactions, signals the host system errors received from controller.
> >
> > Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
> > Signed-off-by: Vikram Garhwal <fnu.vikram@xilinx.com>
> > ---
> >  hw/misc/meson.build                          |   1 +
> >  hw/misc/xlnx-versal-usb2-ctrl-regs.c         | 229
> +++++++++++++++++++++++++++
> >  include/hw/misc/xlnx-versal-usb2-ctrl-regs.h |  45 ++++++
> 
> This seems a bit odd. If it's a USB device (or part of a USB
> device) then it should be under hw/usb, shouldn't it?
[Sai Pavan Boddu] This is a top level wrapper over hcd-dwc3 device, which is specific to versal soc. It's mostly dummy which controls the phy-reset and does frame length adjustments. It was added just to make guest happy, that is the reason it has been added to misc devices.
> 
> > +static void ir_status_postw(RegisterInfo *reg, uint64_t val64) {
> > +    VersalUsb2CtrlRegs *s = XILINX_VERSAL_USB2_CTRL_REGS(reg->opaque);
> > +    /*
> > +     * TODO: This should also clear USBSTS.HSE field in USB XHCI register.
> > +     * May be combine both the modules.
> > +     */
> 
> What does the hardware for this look like? You've modelled it as two
> completely separate devices (this one and the
> TYPE_USB_DWC3) but would it be closer to the hardware structure to have a
> top-level device which has-a DWC3 ?
[Sai Pavan Boddu] Yes, we can look at it such way. But as its specific to versal SOC, we have crafted it out and stitched them in SOC file.

Regards,
Sai Pavan
> 
> thanks
> -- PMM