From: "Arnd Bergmann" <arnd@arndb.de>
To: "Phil Elwell" <phil@raspberrypi.com>
Cc: "Stefan Wahren" <wahrenst@gmx.net>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"laurent.pinchart" <laurent.pinchart@ideasonboard.com>,
"Will Deacon" <will@kernel.org>, "Christoph Hellwig" <hch@lst.de>,
"Florian Fainelli" <florian.fainelli@broadcom.com>,
"Robin Murphy" <robin.murphy@arm.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
linux-staging@lists.linux.dev
Subject: Re: WARNING: drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:364 vchiq_prepare_bulk_data
Date: Mon, 10 Jun 2024 11:00:12 +0200 [thread overview]
Message-ID: <72a414e4-4cd0-4b12-a662-cb73d1e3515e@app.fastmail.com> (raw)
In-Reply-To: <CAMEGJJ3BqY9=9cq_JpKTVhyWKO50hcbEK0MXkBcYZwqadciGiA@mail.gmail.com>
On Mon, Jun 10, 2024, at 10:26, Phil Elwell wrote:
> On Mon, 10 Jun 2024 at 07:00, Arnd Bergmann <arnd@arndb.de> wrote:
>
> Why is swiotlb involved at all? The DMA controller on BCM2837 can
> access all RAM that is visible to the ARM cores.
When a device is not cache-coherent and the buffer is not
cache aligned, we now use swiotlb to avoid clobbering data
in the same cache line during DMA synchronization.
We used to rely on kmalloc() returning buffers that are
cacheline aligned, but that was very expensive.
Arnd
next prev parent reply other threads:[~2024-06-10 9:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-09 22:24 WARNING: drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:364 vchiq_prepare_bulk_data Stefan Wahren
2024-06-10 6:00 ` Arnd Bergmann
2024-06-10 8:26 ` Phil Elwell
2024-06-10 9:00 ` Arnd Bergmann [this message]
2024-06-10 9:15 ` Laurent Pinchart
2024-06-10 9:19 ` Arnd Bergmann
2024-06-10 9:24 ` Phil Elwell
2024-06-10 10:09 ` Arnd Bergmann
2024-06-10 10:25 ` Robin Murphy
2024-06-11 10:47 ` Stefan Wahren
2024-06-11 11:08 ` Arnd Bergmann
2024-06-11 11:37 ` Stefan Wahren
2024-06-11 12:14 ` Arnd Bergmann
2024-06-11 13:09 ` Stefan Wahren
2024-06-11 13:35 ` Robin Murphy
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