Re: [RFC PATCH] USB:XHCI:Modify XHCI driver for USB2.0 controller

liulongfang
2021-02-27T03:35:46Z

On 2021/2/26 17:22, Mathias Nyman wrote:
> On 26.2.2021 10.21, Longfang Liu wrote:
>> Our current XHCI hardware controller has been customized to only
>> support USB 2.0 ports. When using the current xhci driver, an xhci
>> controller device and an ehci controller device will be created
>> automatically. We want the driver to create only one ehci controller.
>> After modifying the driver as follows, an error will occur.
>> Is there any other modification method?
>
> The xhci driver relies on the existence of both a main and a shared hcd.
> One hcd for handing USB 2 (and slower) and the other for USB 3 devices.
>
> As one example xhci_run(hcd) needs to be called for both hcds, first call
> sets up things, second one calls xhci_start() that makes the controller run.
>
> It's probably possible to modify the driver to support xHCI hosts with only
> USB 2 ports, but requires a lot more work.
>
>>
>> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
>> ---
>> drivers/usb/host/xhci-pci.c | 15 ++-------------
>> 1 file changed, 2 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
>> index ef513c2..7296aad 100644
>> --- a/drivers/usb/host/xhci-pci.c
>> +++ b/drivers/usb/host/xhci-pci.c
>> @@ -364,26 +364,15 @@ static int xhci_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
>> /* USB 2.0 roothub is stored in the PCI device now. */
>> hcd = dev_get_drvdata(&dev->dev);
>> xhci = hcd_to_xhci(hcd);
>> - xhci->shared_hcd = usb_create_shared_hcd(&xhci_pci_hc_driver, &dev->dev,
>> - pci_name(dev), hcd);
>> - if (!xhci->shared_hcd) {
>> - retval = -ENOMEM;
>> - goto dealloc_usb2_hcd;
>> - }
>> -
>> + xhci->shared_hcd = NULL;
>> retval = xhci_ext_cap_init(xhci);
>> if (retval)
>> goto put_usb3_hcd;
>>
>> - retval = usb_add_hcd(xhci->shared_hcd, dev->irq,
>> + retval = usb_add_hcd(xhci->main_hcd, dev->irq,
>> IRQF_SHARED);
>> if (retval)
>> goto put_usb3_hcd;
>> - /* Roothub already marked as USB 3.0 speed */
>> -
>> - if (!(xhci->quirks & XHCI_BROKEN_STREAMS) &&
>> - HCC_MAX_PSA(xhci->hcc_params) >= 4)
>> - xhci->shared_hcd->can_do_streams = 1;
>>
>> /* USB-2 and USB-3 roothubs initialized, allow runtime pm suspend */
>> pm_runtime_put_noidle(&dev->dev);
>>
>
> Something like the above could of course not be accepted upstream. We can't break existing
> functionality to support one modified xHCI.
>
> Thanks
> Mathias
> .
>
Thanks very much.
Longfang Liu