[PATCH 02/12] bcm2835-dma: Add proper 40-bit DMA support

[Dave Stevenson]

Hi Stefan and Andrea

On Mon, 5 Feb 2024 at 18:50, Stefan Wahren <wahrenst at gmx.net> wrote:
>
> Hi Andrea,
>
> [add Dave]
>
> Am 04.02.24 um 07:59 schrieb Andrea della Porta:
> > From: Phil Elwell <phil at raspberrypi.org>
> >
> > BCM2711 has 4 DMA channels with a 40-bit address range, allowing them
> > to access the full 4GB of memory on a Pi 4.
> >
> > Cc: Phil Elwell <phil at raspberrypi.org>
> > Cc: Maxime Ripard <maxime at cerno.tech>
> > Signed-off-by: Andrea della Porta <andrea.porta at suse.com>
> mainlining isn't that simple by sending just the downstream patches to
> the mailing list. In many cases there reasons why this hasn't been
> upstreamed yet.
>
> In my opinion just this feature is worth a separate patch series. In
> 2021 i already send an initial version, which tried to implement it in a
> cleaner & maintainabler way [1]. In the meantime Dave Stevenson from
> Raspberry Pi wrote that he also wanted to work on this. Maybe you want
> to work on this together?

Yes, I'm looking at reworking Stefan's series to work on Pi4 & Pi5 as
it's needed for HDMI audio (and other things) on those platforms which
I'm working to upstream.

I was getting weirdness from the sdhci block when I was last looking
at it, so it was just proving a little trickier than first thought.
Hopefully I'll get some time on it in the next couple of weeks.

  Dave

> [1] -
> https://lore.kernel.org/linux-arm-kernel/13ec386b-2305-27da-9765-8fa3ad71146c@i2se.com/T/