[External] - Re: Issues with bcm2835-host: let firmware manage the clock divisor

[Vincent Fazio]

Stefan

> -----Original Message-----
> From: Stefan Wahren <stefan.wahren at i2se.com>
> Sent: Tuesday, May 16, 2023 12:54 AM
> To: Vincent Fazio <vfazio at xes-inc.com>; Nuno Gonçalves
> <nunog at fr24.com>; u-boot at lists.denx.de; pbrobinson at gmail.com
> Subject: Re: [External] - Re: Issues with bcm2835-host: let firmware manage
> the clock divisor
> 
> Am 15.05.23 um 19:57 schrieb Vincent Fazio:
> > Stefan
> >
> >
> I'm not sure I understand the question here re DT/OF. The "regression" in
> the RPi firmware was noticed both in EDK2 and in U-Boot when reading from
> the SD card. The regression was _not_ apparent in RPi Linux, at least from
> what I recall from my testing at the time, meaning that whatever the RPi
> Linux kernel was doing was working around the issue, which is probably why
> the regression happened in the first place since U-Boot/EDK2 are not targets
> for support from RPF.
> 
> Okay, are you able to list the effected bootchains (starting from RPi firmware
> to Linux)?
> 
> Example for a bootchain:
> 
> RPi firmware -> U-Boot -> Linux

As far as I'm aware, the issue [0] documents :

RPi Firmware -> U-Boot
RPi Firmware -> EDK2
RPi Firmware -> Ultibo

I did not notice degraded performance in RPi Linux, presumably due to clock delegation [1]

If someone is using linux-stable vs RPi Linux, there may be some variation.

This was nearly 2 years ago however, I'm heavily relying on what's been documented in the GH issue [0].
 
[0] https://github.com/raspberrypi/firmware/issues/1619
[1] https://github.com/raspberrypi/firmware/issues/1619#issuecomment-917370376

-Vincent