From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
To: David Airlie <airlied@linux.ie>,
Gerd Hoffmann <kraxel@redhat.com>,
Gurchetan Singh <gurchetansingh@chromium.org>,
Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Daniel Almeida <daniel.almeida@collabora.com>,
Gert Wollny <gert.wollny@collabora.com>,
Tomeu Vizoso <tomeu.vizoso@collabora.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
Rob Herring <robh@kernel.org>,
Steven Price <steven.price@arm.com>,
Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
Gustavo Padovan <gustavo.padovan@collabora.com>,
Daniel Stone <daniel@fooishbar.org>,
virtualization@lists.linux-foundation.org,
Dmitry Osipenko <digetx@gmail.com>
Subject: Re: [PATCH v2 4/8] drm/virtio: Improve DMA API usage for shmem BOs
Date: Thu, 17 Mar 2022 04:09:03 +0300 [thread overview]
Message-ID: <eb421bd0-0ff8-1ca6-b14a-2a9bde21c4d8@collabora.com> (raw)
In-Reply-To: <20220314224253.236359-5-dmitry.osipenko@collabora.com>
On 3/15/22 01:42, Dmitry Osipenko wrote:
> DRM API requires the DRM's driver to be backed with the device that can
> be used for generic DMA operations. The VirtIO-GPU device can't perform
> DMA operations if it uses PCI transport because PCI device driver creates
> a virtual VirtIO-GPU device that isn't associated with the PCI. Use PCI's
> GPU device for the DRM's device instead of the VirtIO-GPU device and drop
> DMA-related hacks from the VirtIO-GPU driver.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
> drivers/gpu/drm/virtio/virtgpu_drv.c | 22 +++++++---
> drivers/gpu/drm/virtio/virtgpu_drv.h | 5 +--
> drivers/gpu/drm/virtio/virtgpu_kms.c | 7 ++--
> drivers/gpu/drm/virtio/virtgpu_object.c | 56 +++++--------------------
> drivers/gpu/drm/virtio/virtgpu_vq.c | 13 +++---
> 5 files changed, 37 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index 5f25a8d15464..8449dad3e65c 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -46,9 +46,9 @@ static int virtio_gpu_modeset = -1;
> MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
> module_param_named(modeset, virtio_gpu_modeset, int, 0400);
>
> -static int virtio_gpu_pci_quirk(struct drm_device *dev, struct virtio_device *vdev)
> +static int virtio_gpu_pci_quirk(struct drm_device *dev)
Somehow I missed that virtio_gpu_pci_quirk() contains comment telling
about why dev.parent isn't used for the DRM's device.
/*
* Normally the drm_dev_set_unique() call is done by core DRM.
* The following comment covers, why virtio cannot rely on it.
*
* Unlike the other virtual GPU drivers, virtio abstracts the
* underlying bus type by using struct virtio_device.
*
* Hence the dev_is_pci() check, used in core DRM, will fail
* and the unique returned will be the virtio_device "virtio0",
* while a "pci:..." one is required.
*
* A few other ideas were considered:
* - Extend the dev_is_pci() check [in drm_set_busid] to
* consider virtio.
* Seems like a bigger hack than what we have already.
*
* - Point drm_device::dev to the parent of the virtio_device
* Semantic changes:
* * Using the wrong device for i2c, framebuffer_alloc and
* prime import.
* Visual changes:
* * Helpers such as DRM_DEV_ERROR, dev_info, drm_printer,
* will print the wrong information.
*
* We could address the latter issues, by introducing
* drm_device::bus_dev, ... which would be used solely for this.
*
* So for the moment keep things as-is, with a bulky comment
* for the next person who feels like removing this
* drm_dev_set_unique() quirk.
*/
There is no I2C, nor prime import support and framebuffer_alloc hasn't
been used for years now. I guess prime import actually will want the
real device and not the virtio_device if GEM importing will be ever
supported by VirtIO-GPU driver. Apparently this comment was outdated a
long time ago and the "visual changes" aren't too important, the
messages now says "virtio-pci 0000:00:02.0" instead of "virtio_gpu virtio0".
I'll remove the comment and drm_dev_set_unique() quirk in v3.
next prev parent reply other threads:[~2022-03-17 1:09 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-14 22:42 [PATCH v2 0/8] Add memory shrinker to VirtIO-GPU DRM driver Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 1/8] drm/virtio: Correct drm_gem_shmem_get_sg_table() error handling Dmitry Osipenko
2022-03-15 13:05 ` Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 2/8] drm/virtio: Check whether transferred 2D BO is shmem Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 3/8] drm/virtio: Unlock GEM reservations in error code path Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 4/8] drm/virtio: Improve DMA API usage for shmem BOs Dmitry Osipenko
2022-03-16 12:41 ` Robin Murphy
2022-03-16 13:52 ` Dmitry Osipenko
2022-03-17 1:09 ` Dmitry Osipenko [this message]
2022-03-14 22:42 ` [PATCH v2 5/8] drm/shmem-helper: Correct doc-comment of drm_gem_shmem_get_sg_table() Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 6/8] drm/shmem-helper: Add generic memory shrinker Dmitry Osipenko
2022-03-16 15:04 ` Steven Price
2022-03-16 23:03 ` Dmitry Osipenko
2022-03-16 20:00 ` Rob Clark
2022-03-17 0:13 ` Dmitry Osipenko
2022-03-17 16:13 ` Rob Clark
2022-03-17 17:43 ` Dmitry Osipenko
2022-03-17 17:32 ` Daniel Vetter
2022-03-17 17:45 ` Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 7/8] drm/virtio: Support memory shrinking Dmitry Osipenko
2022-03-15 12:43 ` Emil Velikov
2022-03-16 14:23 ` Dmitry Osipenko
2022-03-14 22:42 ` [PATCH v2 8/8] drm/panfrost: Switch to generic memory shrinker Dmitry Osipenko
2022-03-14 23:26 ` Alyssa Rosenzweig
2022-03-14 23:32 ` Dmitry Osipenko
2022-03-16 15:04 ` Steven Price
2022-03-16 23:04 ` Dmitry Osipenko
2022-03-18 14:41 ` Dmitry Osipenko
2022-03-18 14:47 ` Steven Price
2022-03-18 17:09 ` Dmitry Osipenko
2022-03-15 12:47 ` [PATCH v2 0/8] Add memory shrinker to VirtIO-GPU DRM driver Emil Velikov
2022-03-15 13:10 ` Dmitry Osipenko
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