From 143ec8d3f93965110689897f0d25165dc9664009 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Fri, 7 Mar 2025 09:03:59 +0100 Subject: drm/prime: Support dedicated DMA device for dma-buf imports Importing dma-bufs via PRIME requires a DMA-capable device. Devices on peripheral busses, such as USB, often cannot perform DMA by themselves. Without DMA-capable device PRIME import fails. DRM drivers for USB devices already use a separate DMA device for dma-buf imports. Make the mechanism generally available. Besides the case of USB, there are embedded DRM devices without DMA capability. DMA is performed by a separate controller. DRM drivers should set this accordingly. Add the field dma_dev to struct drm_device to refer to the device's DMA device. For USB this should be the USB controller. Use dma_dev in the PRIME import helpers, if set. v2: - acquire internal reference on dma_dev (Jani) - add DMA-controller usecase to docs (Maxime) Signed-off-by: Thomas Zimmermann Reviewed-by: Jani Nikula Reviewed-by: Maxime Ripard Link: https://patchwork.freedesktop.org/patch/msgid/20250307080836.42848-2-tzimmermann@suse.de --- drivers/gpu/drm/drm_drv.c | 21 +++++++++++++++++++++ drivers/gpu/drm/drm_prime.c | 2 +- 2 files changed, 22 insertions(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 17fc5dc708f4..c9487bc88624 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -500,6 +500,25 @@ void drm_dev_unplug(struct drm_device *dev) } EXPORT_SYMBOL(drm_dev_unplug); +/** + * drm_dev_set_dma_dev - set the DMA device for a DRM device + * @dev: DRM device + * @dma_dev: DMA device or NULL + * + * Sets the DMA device of the given DRM device. Only required if + * the DMA device is different from the DRM device's parent. After + * calling this function, the DRM device holds a reference on + * @dma_dev. Pass NULL to clear the DMA device. + */ +void drm_dev_set_dma_dev(struct drm_device *dev, struct device *dma_dev) +{ + dma_dev = get_device(dma_dev); + + put_device(dev->dma_dev); + dev->dma_dev = dma_dev; +} +EXPORT_SYMBOL(drm_dev_set_dma_dev); + /* * Available recovery methods for wedged device. To be sent along with device * wedged uevent. @@ -654,6 +673,8 @@ static void drm_dev_init_release(struct drm_device *dev, void *res) { drm_fs_inode_free(dev->anon_inode); + put_device(dev->dma_dev); + dev->dma_dev = NULL; put_device(dev->dev); /* Prevent use-after-free in drm_managed_release when debugging is * enabled. Slightly awkward, but can't really be helped. */ diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index a3d64f93a225..4b8c6075e46a 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -997,7 +997,7 @@ EXPORT_SYMBOL(drm_gem_prime_import_dev); struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, struct dma_buf *dma_buf) { - return drm_gem_prime_import_dev(dev, dma_buf, dev->dev); + return drm_gem_prime_import_dev(dev, dma_buf, drm_dev_dma_dev(dev)); } EXPORT_SYMBOL(drm_gem_prime_import); -- cgit v1.2.3