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From: Greg KH <gregkh@linuxfoundation.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Pavel Machek <pavel@ucw.cz>,
	airlied@linux.ie, Daniel Vetter <daniel.vetter@ffwll.ch>,
	Christoph Hellwig <hch@lst.de>,
	hdegoede@redhat.com, stern@rowland.harvard.edu,
	dri-devel@lists.freedesktop.org, stable@vger.kernel.org,
	sean@poorly.run, christian.koenig@amd.com
Subject: Re: [PATCH v6] drm: Use USB controller's DMA mask when importing dmabufs
Date: Tue, 2 Mar 2021 10:56:17 +0100	[thread overview]
Message-ID: <YD4Lwbcb9Q5Wv/Xc@kroah.com> (raw)
In-Reply-To: <20210301093127.11028-1-tzimmermann@suse.de>

On Mon, Mar 01, 2021 at 10:31:27AM +0100, Thomas Zimmermann wrote:
> USB devices cannot perform DMA and hence have no dma_mask set in their
> device structure. Therefore importing dmabuf into a USB-based driver
> fails, which breaks joining and mirroring of display in X11.
> 
> For USB devices, pick the associated USB controller as attachment device.
> This allows the DRM import helpers to perform the DMA setup. If the DMA
> controller does not support DMA transfers, we're out of luck and cannot
> import. Our current USB-based DRM drivers don't use DMA, so the actual
> DMA device is not important.
> 
> Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their
> instance of struct drm_driver.
> 
> Tested by joining/mirroring displays of udl and radeon un der Gnome/X11.
> 
> v6:
> 	* implement workaround in DRM drivers and hold reference to
> 	  DMA device while USB device is in use
> 	* remove dev_is_usb() (Greg)
> 	* collapse USB helper into usb_intf_get_dma_device() (Alan)
> 	* integrate Daniel's TODO statement (Daniel)
> 	* fix typos (Greg)
> v5:
> 	* provide a helper for USB interfaces (Alan)
> 	* add FIXME item to documentation and TODO list (Daniel)
> v4:
> 	* implement workaround with USB helper functions (Greg)
> 	* use struct usb_device->bus->sysdev as DMA device (Takashi)
> v3:
> 	* drop gem_create_object
> 	* use DMA mask of USB controller, if any (Daniel, Christian, Noralf)
> v2:
> 	* move fix to importer side (Christian, Daniel)
> 	* update SHMEM and CMA helpers for new PRIME callbacks
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices")
> Tested-by: Pavel Machek <pavel@ucw.cz>
> Acked-by: Christian König <christian.koenig@amd.com>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: <stable@vger.kernel.org> # v5.10+
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: daniel@ffwll.ch, airlied@linux.ie,
	maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	sumit.semwal@linaro.org, christian.koenig@amd.com,
	hdegoede@redhat.com, sean@poorly.run, noralf@tronnes.org,
	stern@rowland.harvard.edu, dri-devel@lists.freedesktop.org,
	Pavel Machek <pavel@ucw.cz>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Christoph Hellwig <hch@lst.de>,
	stable@vger.kernel.org
Subject: Re: [PATCH v6] drm: Use USB controller's DMA mask when importing dmabufs
Date: Tue, 2 Mar 2021 10:56:17 +0100	[thread overview]
Message-ID: <YD4Lwbcb9Q5Wv/Xc@kroah.com> (raw)
In-Reply-To: <20210301093127.11028-1-tzimmermann@suse.de>

On Mon, Mar 01, 2021 at 10:31:27AM +0100, Thomas Zimmermann wrote:
> USB devices cannot perform DMA and hence have no dma_mask set in their
> device structure. Therefore importing dmabuf into a USB-based driver
> fails, which breaks joining and mirroring of display in X11.
> 
> For USB devices, pick the associated USB controller as attachment device.
> This allows the DRM import helpers to perform the DMA setup. If the DMA
> controller does not support DMA transfers, we're out of luck and cannot
> import. Our current USB-based DRM drivers don't use DMA, so the actual
> DMA device is not important.
> 
> Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their
> instance of struct drm_driver.
> 
> Tested by joining/mirroring displays of udl and radeon un der Gnome/X11.
> 
> v6:
> 	* implement workaround in DRM drivers and hold reference to
> 	  DMA device while USB device is in use
> 	* remove dev_is_usb() (Greg)
> 	* collapse USB helper into usb_intf_get_dma_device() (Alan)
> 	* integrate Daniel's TODO statement (Daniel)
> 	* fix typos (Greg)
> v5:
> 	* provide a helper for USB interfaces (Alan)
> 	* add FIXME item to documentation and TODO list (Daniel)
> v4:
> 	* implement workaround with USB helper functions (Greg)
> 	* use struct usb_device->bus->sysdev as DMA device (Takashi)
> v3:
> 	* drop gem_create_object
> 	* use DMA mask of USB controller, if any (Daniel, Christian, Noralf)
> v2:
> 	* move fix to importer side (Christian, Daniel)
> 	* update SHMEM and CMA helpers for new PRIME callbacks
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices")
> Tested-by: Pavel Machek <pavel@ucw.cz>
> Acked-by: Christian König <christian.koenig@amd.com>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: <stable@vger.kernel.org> # v5.10+
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

  parent reply	other threads:[~2021-03-02  9:56 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-01  9:31 [PATCH v6] drm: Use USB controller's DMA mask when importing dmabufs Thomas Zimmermann
2021-03-01  9:31 ` Thomas Zimmermann
2021-03-02  9:45 ` Thomas Zimmermann
2021-03-02  9:45   ` Thomas Zimmermann
2021-03-02  9:56 ` Greg KH [this message]
2021-03-02  9:56   ` Greg KH
2021-03-03  5:51 ` Dan Carpenter
2021-03-03  5:51   ` Dan Carpenter
2021-03-03  8:25   ` Thomas Zimmermann
  -- strict thread matches above, loose matches on Subject: below --
2021-03-02 18:47 kernel test robot

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