[PATCH v3 1/2] arm: rpi: Add function to trigger VL805's firmware load

[Nicolas Saenz Julienne]

Hi Bin,

On Wed, 2020-05-06 at 13:33 +0800, Bin Meng wrote:
> Hi Nicolas,
> 
> On Wed, May 6, 2020 at 12:26 AM Nicolas Saenz Julienne
> <nsaenzjulienne at suse.de> wrote:
> > On the Raspberry Pi 4, after a PCI reset, VL805's (a xHCI chip) firmware
> > may either be loaded directly from an EEPROM or, if not present, by the
> > SoC's VideCore (the SoC's co-processor). Introduce the function that
> > informs VideCore that VL805 may need its firmware loaded.
> > 
> 
> I still did not get it. Without the firmware being loaded, does xHCI
> on RPi 4 still work?

On newer revisions of RPi4, no, it will not work.

> What exact functionality does the firmware provide?

It provides xHCI functionality.

The old RPi4 design loaded this vl805 firmware trough a dedicated EEPROM
memory. But they removed it, probably in order to save costs. They then created
this new interface to trigger a firmware load from RPi4's co-processor.

Regards,
Nicolas

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