[UBOOT PATCH 1/3] usb: dwc3: core: improve reset sequence

[Michal Simek]

On 6/20/23 22:41, Tom Rini wrote:
> On Tue, Jun 20, 2023 at 08:36:11AM +0200, Michal Simek wrote:
>>
>>
>> On 6/19/23 19:04, Eugen Hristev wrote:
>>> On 6/19/23 19:07, Marek Vasut wrote:
>>>> On 6/19/23 15:26, Eugen Hristev wrote:
>>>>> On 5/8/23 06:00, Venkatesh Yadav Abbarapu wrote:
>>>>>> [ Felipe: Ported from Linux kernel commit
>>>>>>        f59dcab17629 ("usb: dwc3: core: improve reset sequence") ]
>>>>>>
>>>>>> According to Synopsys Databook, we shouldn't be relying on
>>>>>> GCTL.CORESOFTRESET bit as that's only for debugging purposes.
>>>>>> Instead, let's use DCTL.CSFTRST if we're OTG or PERIPHERAL mode.
>>>>>>
>>>>>> Host side block will be reset by XHCI driver if necessary. Note that this
>>>>>> reduces amount of time spent on dwc3_probe() by a long margin.
>>>>>>
>>>>>> We're still gonna wait for reset to finish for a long time
>>>>>> (default to 1ms max), but tests show that the reset polling loop executed
>>>>>> at most 19 times (modprobe dwc3 && modprobe -r dwc3 executed 1000
>>>>>> times in a row).
>>>>>>
>>>>>> Without proper core reset, observing random issues like when the
>>>>>> USB(DWC3) is in device mode, the host device is not able to detect the
>>>>>> USB device.
>>>>>>
>>>>>> Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu at amd.com>
>>>>>> ---
>>>>>>    drivers/usb/dwc3/core.c | 50 +++++++++++++++--------------------------
>>>>>>    1 file changed, 18 insertions(+), 32 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>>>> index 49f6a1900b..8702a54efa 100644
>>>>>> --- a/drivers/usb/dwc3/core.c
>>>>>> +++ b/drivers/usb/dwc3/core.c
>>>>>> @@ -60,42 +60,28 @@ static void dwc3_set_mode(struct dwc3 *dwc, u32 mode)
>>>>>>    static int dwc3_core_soft_reset(struct dwc3 *dwc)
>>>>>>    {
>>>>>>        u32        reg;
>>>>>> +    int        retries = 1000;
>>>>>> -    /* Before Resetting PHY, put Core in Reset */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GCTL);
>>>>>> -    reg |= DWC3_GCTL_CORESOFTRESET;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GCTL, reg);
>>>>>> -
>>>>>> -    /* Assert USB3 PHY reset */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0));
>>>>>> -    reg |= DWC3_GUSB3PIPECTL_PHYSOFTRST;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(0), reg);
>>>>>> -
>>>>>> -    /* Assert USB2 PHY reset */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
>>>>>> -    reg |= DWC3_GUSB2PHYCFG_PHYSOFTRST;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
>>>>>> -
>>>>>> -    mdelay(100);
>>>>>> -
>>>>>> -    /* Clear USB3 PHY reset */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0));
>>>>>> -    reg &= ~DWC3_GUSB3PIPECTL_PHYSOFTRST;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GUSB3PIPECTL(0), reg);
>>>>>> -
>>>>>> -    /* Clear USB2 PHY reset */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
>>>>>> -    reg &= ~DWC3_GUSB2PHYCFG_PHYSOFTRST;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
>>>>>> +    /*
>>>>>> +     * We're resetting only the device side because, if we're in host mode,
>>>>>> +     * XHCI driver will reset the host block. If dwc3 was configured for
>>>>>> +     * host-only mode, then we can return early.
>>>>>> +     */
>>>>>> +    if (dwc->dr_mode == USB_DR_MODE_HOST)
>>>>>> +        return 0;
>>>>>> -    mdelay(100);
>>>>>> +    reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>>>>>> +    reg |= DWC3_DCTL_CSFTRST;
>>>>>> +    dwc3_writel(dwc->regs, DWC3_DCTL, reg);
>>>>>> -    /* After PHYs are stable we can take Core out of reset state */
>>>>>> -    reg = dwc3_readl(dwc->regs, DWC3_GCTL);
>>>>>> -    reg &= ~DWC3_GCTL_CORESOFTRESET;
>>>>>> -    dwc3_writel(dwc->regs, DWC3_GCTL, reg);
>>>>>> +    do {
>>>>>> +        reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>>>>>> +        if (!(reg & DWC3_DCTL_CSFTRST))
>>>>>> +            return 0;
>>>>>> +        udelay(1);
>>>>>> +    } while (--retries);
>>>>>> -    return 0;
>>>>>> +    return -ETIMEDOUT;
>>>>>>    }
>>>>>>    /*
>>>>>
>>>>> Hello Venkatesh, Michal,
>>>>>
>>>>> I randomly found this patch while testing the Dwc3 on rockchip
>>>>> RK3588 , I noticed that you removed the code that resets the
>>>>> PHYs in this patch hence DWC3 is no longer starting in my case.
>>>>> Was this intentional with this patch ?
>>>>
>>>> All of these patches are NAK until the DWC3 is synchronized with
>>>> Linux. Picking random DWC3 patches and ignoring other fixes will
>>>> turn the whole driver into an unmaintainable mess and make the sync
>>>> that much harder in the future. I spent enormous amount of my spare
>>>> time trying to explain to Xilinx how to do that mostly
>>>> automatically, but that was all ignored or countered with reason
>>>> after reason why this cannot be done, but as far as I can tell,
>>>> nobody in Xilinx actually tried the proposal.
>>>>
>>>> Hence, NAK
>>>>
>>>> Hence, no need to worry these patches will be applied in their current state.
>>>
>>> Hi Marek,
>>>
>>> that's fine. No argument from my side.
>>>
>>> What I wanted to actually tell/ask , is the fact that this patch
>>> actually helps in my case, just that it breaks something else, and I
>>> wanted to get more info from the patch authors.
>>>
>>> I am experiencing some situations where dwc3 does not correctly start
>>> unless I add some manual delays here and there, and I am trying to see
>>> why.
>>
>> It is not just about dwc3. There are other parts which are ported from Linux
>> kernel and are out of sync from Linux kernel for quite a long time.
>> Another example is xhci - kernel 3.4.
>> I am little bit worried that the whole usb stack is out of sync.
> 
> Yes, various parts of the stack could use some re-syncing with upstream.
> And I forget if xhci is one of the parts that's done in such a way that
> it should be straight-forward to do so.  But dwc3 is. And while I can
> see that there would be concerns about getting changes tested
> sufficiently for something broad like that, that's what the merge window
> is for.  So why can't AMD re-sync things, test on your platforms and
> have the community test on the rest?  It should also come out fairly
> quickly if there's more broad changes needed, and that in turn would be
> good to know so we know what's next here.

Marek is saying that it is going to be easy task. You are saying fairly quickly.

The commit 85d5e7075f33e97079886027104591ff53d6363b is saying that patch taken 
from 3.19-rc1 (97bf6af1f9)

Just simple git log shows that from that time 1160 patches has been applied there.
$ git log --oneline --no-merges 97bf6af1f9..linux-next/master drivers/usb/dwc3/ 
| wc -l
1160

U-Boot logs from the initial commit on this folder is showing addition 159 patches
$ git log --oneline --no-merges drivers/usb/dwc3/ | wc -l
159

It means diff is 1000 patches. I expect a lot of patches can be ignored, some of 
them are backports already but I wouldn't consider it as an easy task for non 
USB expects.

Thanks,
Michal