[PATCH v1] HSD #18028953892: usb: xhci-dwc3: Fix USB3.1 controller register access in reset state

[Marek Vasut]

On 6/22/23 04:48, Lim, Jit Loon wrote:
>> -----Original Message-----
>> From: Marek Vasut <marex at denx.de>
>> Sent: Wednesday, 21 June, 2023 10:19 PM
>> To: Lim, Jit Loon <jit.loon.lim at intel.com>; u-boot at lists.denx.de
>> Cc: Jagan Teki <jagan at amarulasolutions.com>; Simon
>> <simon.k.r.goldschmidt at gmail.com>; Chee, Tien Fong
>> <tien.fong.chee at intel.com>; Hea, Kok Kiang <kok.kiang.hea at intel.com>;
>> Lokanathan, Raaj <raaj.lokanathan at intel.com>; Maniyam, Dinesh
>> <dinesh.maniyam at intel.com>; Ng, Boon Khai <boon.khai.ng at intel.com>;
>> Yuslaimi, Alif Zakuan <alif.zakuan.yuslaimi at intel.com>; Chong, Teik Heng
>> <teik.heng.chong at intel.com>; Zamri, Muhammad Hazim Izzat
>> <muhammad.hazim.izzat.zamri at intel.com>; Tang, Sieu Mun
>> <sieu.mun.tang at intel.com>; Bin Meng <bmeng.cn at gmail.com>
>> Subject: Re: [PATCH v1] HSD #18028953892: usb: xhci-dwc3: Fix USB3.1
>> controller register access in reset state
>>
>> On 6/21/23 16:11, Jit Loon Lim wrote:
>>> From: Teik Heng Chong <teik.heng.chong at intel.com>
>>>
>>> The controller registers should not be accessed while the controller's
>>> vcc_reset_n is asserted.
>>>
>>> Signed-off-by: Teik Heng Chong <teik.heng.chong at intel.com>
>>
>> Is this patch ported from Linux or is this custom development ?
>>
>> Is there a matching patch/fix in Linux already ?
> 
> In xhci_dwc3_probe(), the program sequence is
> vcc reset -> clk init -> phy setup -> xhci_register
> therefore, when xhci_dwc3_remove is called, the proper usb stop sequence should be
> xhci_register _> phy setup -> clk init -> vcc reset
> 
> if we look at linux driver  https://elixir.bootlin.com/linux/latest/source/drivers/usb/dwc3/dwc3-of-simple.c#L33
> 
> dwc3_of_simple_probe: The sequence is reset -> clock
> __dwc3_of_simple_teardown: Then, clock -> reset
> 
> So based on the above, we have made changes and the uboot fix is now aligned with linux driver.

Instead of adding random patches to the U-Boot dwc3 driver, please just 
synchronize the driver with Linux. You should be able to add the missing 
patches to the DWC3 driver from Linux since the last synchronization 
point, the process should be largely mechanical. Make sure to include 
commit ID of each Linux commit in the new matching U-Boot patch.

It shouldn't be difficult, one approach I can think of is roughly this:
- figure out the original merge base from which the DWC3 driver was 
imported to U-Boot
- in U-Boot, revert all dwc3 patches on top of that import patch
- pick all Linux kernel dwc3 patches from that merge base and apply on 
top of this U-Boot with reverts
- Run rebase and drop the reverts, let git drop duplicate patches