Re: [PATCH 09/11] usb: dwc2: Skip clock gating on Broadcom SoCs

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Hi,

On 7/5/24 10:21, Stefan Wahren wrote:
Hi Jeremy,

Am 05.07.24 um 17:03 schrieb Lukas Wunner:
On Fri, Jul 05, 2024 at 12:22:33PM +0200, Stefan Wahren wrote:
Am 05.07.24 um 10:48 schrieb Lukas Wunner:
The real question is whether BCM2848 platforms likewise cannot disable
the clock of the dwc2 controller or whether this is specific to the
BCM2835.  Right now dwc2_set_bcm_params() is applied to both the
BCM2848 and BCM2835.  If the BCM2848 behaves differently in this
regard, we'd have to duplicate dwc2_set_bcm_params() for the BCM2835.
 From my understand BCM2848 refers to the same SoC, but the ACPI
implementation uses a different ID [2]. So I think this is safe.
[2] -
https://patches.linaro.org/project/linux-usb/patch/20210413215834.3126447-2-jeremy.linton@xxxxxxx/
Careful there, the patch vaguely says...

     With that added and identified as "BCM2848",
     an id in use by other OSs for this device, the dw2
     controller on the BCM2711 will work.

...which sounds like they copy-pasted the BCM2848 id from somewhere else.
I would assume that BCM2848 is really a different SoC and not just
a different name for the BCM2835, but hopefully BroadCom folks will
be able to confirm or deny this (and thus the necessity of the quirk
on BCM2848 and not just on BCM2835).
could you please clarify this situation?

This id comes from the edk2-platforms ACPI tables and is currently used by both the rpi3 and rpi4, and AFAIK nothing else as the rpi5-dev work is currently only exposing XHCI.

The ID is strictly the USB controller not the SoC. Its a bit confusingly named, but something we inherited from the much older windows/edk2 port, where it appears that the peripheral HID's were just picked in numerical order.

[0] https://github.com/tianocore/edk2-platforms/blob/12f68d29abdc9d703f67bd743fdec23ebb1e966e/Platform/RaspberryPi/AcpiTables/GpuDevs.asl#L15





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