From: Christoph Hellwig <hch@infradead.org>
To: Icenowy Zheng <uwu@icenowy.me>
Cc: "Bjorn Helgaas" <helgaas@kernel.org>,
"Jiaxun Yang" <jiaxun.yang@flygoat.com>,
"Christian König" <christian.koenig@amd.com>,
"Huang Rui" <ray.huang@amd.com>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Maxime Ripard" <mripard@kernel.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"David Airlie" <airlied@gmail.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
bhelgaas@google.com, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: PCIe coherency in spec (was: [RFC PATCH 2/2] drm/ttm: downgrade cached to write_combined when snooping not available)
Date: Wed, 3 Jul 2024 23:11:41 -0700 [thread overview]
Message-ID: <ZoY9HZwon3_yiq6F@infradead.org> (raw)
In-Reply-To: <99ff395019901c5c1a7b298481c8261b30fdbd01.camel@icenowy.me>
On Thu, Jul 04, 2024 at 10:00:52AM +0800, Icenowy Zheng wrote:
> So I here want to ask a question as an individual hacker: what's the
> policy of linux-pci towards these non-coherent PCIe implementations?
>
> If the sentences of Christian is right, these implementations are just
> out-of-spec, should them get purged out of the kernel, or at least
> raising a warning that some HW won't work because of inconformant
> implementation?
Nothing in the PCIe specifications that mandates a programming model.
Non-coherent DMA is extremely common in lower end devices, and despite
all the issues that it causes well supported in Linux.
What are you trying to solve?
next prev parent reply other threads:[~2024-07-04 6:11 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-29 5:22 [RFC PATCH 0/2] drm/ttm: support device w/o coherency Icenowy Zheng
2024-06-29 5:22 ` [RFC PATCH 1/2] drm/ttm: save the device's DMA coherency status in ttm_device Icenowy Zheng
2024-06-29 5:22 ` [RFC PATCH 2/2] drm/ttm: downgrade cached to write_combined when snooping not available Icenowy Zheng
2024-06-29 19:57 ` Jiaxun Yang
2024-06-29 20:51 ` Icenowy Zheng
2024-07-01 11:40 ` Christian König
2024-07-01 11:52 ` Jiaxun Yang
2024-07-01 12:10 ` Christian König
2024-07-02 1:46 ` Icenowy Zheng
[not found] ` <ff1bf596-83cb-4b3e-a33a-621ac2c8171c@amd.com>
2024-07-02 9:06 ` Icenowy Zheng
[not found] ` <ae7085fd-3bca-4a4a-b465-5e4941011877@amd.com>
2024-07-02 10:01 ` Icenowy Zheng
2024-07-02 10:03 ` Jiaxun Yang
2024-07-03 8:52 ` PCIe coherency in spec (was: [RFC PATCH 2/2] drm/ttm: downgrade cached to write_combined when snooping not available) Jiaxun Yang
2024-07-03 21:08 ` Bjorn Helgaas
2024-07-04 2:00 ` Icenowy Zheng
2024-07-04 6:11 ` Christoph Hellwig [this message]
2024-07-04 6:40 ` Icenowy Zheng
2024-07-04 6:44 ` Christoph Hellwig
[not found] ` <4e958aa5-2a56-4754-b3dd-273da95f1d14@amd.com>
2024-07-02 9:36 ` [RFC PATCH 2/2] drm/ttm: downgrade cached to write_combined when snooping not available Icenowy Zheng
2024-06-30 6:52 ` Icenowy Zheng
2024-07-01 11:37 ` [RFC PATCH 0/2] drm/ttm: support device w/o coherency Christian König
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