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From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Tue, 6 Feb 2024 16:31:06 +0000
Message-ID: <CAPY8ntCEvsTJwoEBYc7JsTaYfdMURhmytvvVMcLVNBkmdTNcZQ@mail.gmail.com>
Subject: Re: [PATCH 02/12] bcm2835-dma: Add proper 40-bit DMA support
To: Stefan Wahren <wahrenst@gmx.net>
Cc: Andrea della Porta <andrea.porta@suse.com>, Vinod Koul <vkoul@kernel.org>, 
	Florian Fainelli <florian.fainelli@broadcom.com>, Ray Jui <rjui@broadcom.com>, 
	Scott Branden <sbranden@broadcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>, dmaengine@vger.kernel.org, 
	linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, 
	linux-kernel@vger.kernel.org, Maxime Ripard <maxime@cerno.tech>, 
	Dom Cobley <popcornmix@gmail.com>, Phil Elwell <phil@raspberrypi.com>
Content-Type: text/plain; charset="UTF-8"

Hi Stefan and Andrea

On Mon, 5 Feb 2024 at 18:50, Stefan Wahren <wahrenst@gmx.net> wrote:
>
> Hi Andrea,
>
> [add Dave]
>
> Am 04.02.24 um 07:59 schrieb Andrea della Porta:
> > From: Phil Elwell <phil@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@raspberrypi.org>
> > Cc: Maxime Ripard <maxime@cerno.tech>
> > Signed-off-by: Andrea della Porta <andrea.porta@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/