From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
amd-gfx@lists.freedesktop.org,
Christian Koenig <christian.koenig@amd.com>,
Alex Deucher <alexander.deucher@amd.com>,
David Zhou <David1.Zhou@amd.com>, Huang Rui <ray.huang@amd.com>,
Junwei Zhang <Jerry.Zhang@amd.com>,
Michel Daenzer <michel.daenzer@amd.com>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Sean Paul <sean@poorly.run>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [RFC PATCH] drm: disable WC optimization for cache coherent devices on non-x86
Date: Mon, 21 Jan 2019 16:33:27 +0100 [thread overview]
Message-ID: <CAKv+Gu-hR=uieOeg7QheA5yfAycUoi2vjZsDUvROKVjW4eUNqw@mail.gmail.com> (raw)
In-Reply-To: <20190121150734.GA30582@infradead.org>
On Mon, 21 Jan 2019 at 16:07, Christoph Hellwig <hch@infradead.org> wrote:
>
> > +#include <linux/dma-noncoherent.h>
>
> This header is not for usage in device drivers, but purely for
> dma-mapping implementations!
>
Is that documented anywhere?
> > +static inline bool drm_device_can_wc_memory(struct drm_device *ddev)
> > {
> > + if (IS_ENABLED(CONFIG_PPC))
> > + return IS_ENABLED(CONFIG_NOT_COHERENT_CACHE);
> > + else if (IS_ENABLED(CONFIG_MIPS))
> > + return !IS_ENABLED(CONFIG_CPU_LOONGSON3);
> > + else if (IS_ENABLED(CONFIG_X86))
> > + return true;
> > +
> > + return !dev_is_dma_coherent(ddev->dev);
>
> And even if something like this was valid to do, it would have to be
> a core function with an arch hook, and not hidden in a random driver.
Why would it not be valid to do? Is it wrong for a driver to be aware
of whether a device is cache coherent or not?
And in case it isn't, do you have an alternative suggestion on how to
fix this mess?
next prev parent reply other threads:[~2019-01-21 15:33 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-21 10:06 [RFC PATCH] drm: disable WC optimization for cache coherent devices on non-x86 Ard Biesheuvel
2019-01-21 10:11 ` Koenig, Christian
2019-01-21 15:07 ` Christoph Hellwig
2019-01-21 15:33 ` Ard Biesheuvel [this message]
2019-01-21 15:59 ` Christoph Hellwig
2019-01-21 16:14 ` Ard Biesheuvel
2019-01-21 16:22 ` Christoph Hellwig
2019-01-21 16:30 ` Ard Biesheuvel
2019-01-21 16:35 ` Christoph Hellwig
2019-01-21 16:50 ` Ard Biesheuvel
2019-01-21 17:55 ` Michel Dänzer
2019-01-21 17:59 ` Ard Biesheuvel
2019-01-21 18:04 ` Michel Dänzer
2019-01-21 18:20 ` Ard Biesheuvel
2019-01-21 18:23 ` Michel Dänzer
2019-01-21 18:28 ` Ard Biesheuvel
2019-01-21 19:04 ` Michel Dänzer
2019-01-21 19:18 ` Ard Biesheuvel
2019-01-22 8:38 ` Ard Biesheuvel
2019-01-22 20:56 ` Alex Deucher
2019-01-22 21:07 ` Ard Biesheuvel
2019-01-23 7:15 ` Christoph Hellwig
2019-01-23 9:08 ` Ard Biesheuvel
2019-01-23 16:44 ` Christoph Hellwig
2019-01-23 16:52 ` Ard Biesheuvel
2019-01-24 9:13 ` Christoph Hellwig
2019-01-24 9:25 ` Koenig, Christian
2019-01-24 9:28 ` Ard Biesheuvel
2019-01-24 9:45 ` Koenig, Christian
2019-01-24 9:59 ` Ard Biesheuvel
2019-01-24 11:23 ` Koenig, Christian
2019-01-24 11:26 ` Ard Biesheuvel
2019-01-24 11:37 ` Koenig, Christian
2019-01-24 11:45 ` Ard Biesheuvel
2019-01-24 13:54 ` Alex Deucher
2019-01-24 13:57 ` Ard Biesheuvel
2019-01-24 14:00 ` Alex Deucher
2019-01-24 16:04 ` Michel Dänzer
2019-01-24 9:31 ` Michel Dänzer
2019-01-24 9:37 ` Ard Biesheuvel
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