| Message ID | 20250307080836.42848-2-tzimmermann@suse.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | drm: Provide a dedicated DMA device for PRIME import | expand |
On Fri, 07 Mar 2025, Thomas Zimmermann <tzimmermann@suse.de> wrote: > 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 <tzimmermann@suse.de> Reviewed-by: Jani Nikula <jani.nikula@intel.com> > --- > drivers/gpu/drm/drm_drv.c | 21 +++++++++++++++++++ > drivers/gpu/drm/drm_prime.c | 2 +- > include/drm/drm_device.h | 41 +++++++++++++++++++++++++++++++++++++ > 3 files changed, 63 insertions(+), 1 deletion(-) > > 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 bdb51c8f262e..ed4e5f06b79d 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -998,7 +998,7 @@ 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); > > diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h > index 6ea54a578cda..e2f894f1b90a 100644 > --- a/include/drm/drm_device.h > +++ b/include/drm/drm_device.h > @@ -64,6 +64,28 @@ struct drm_device { > /** @dev: Device structure of bus-device */ > struct device *dev; > > + /** > + * @dma_dev: > + * > + * Device for DMA operations. Only required if the device @dev > + * cannot perform DMA by itself. Should be NULL otherwise. Call > + * drm_dev_dma_dev() to get the DMA device instead of using this > + * field directly. Call drm_dev_set_dma_dev() to set this field. > + * > + * DRM devices are sometimes bound to virtual devices that cannot > + * perform DMA by themselves. Drivers should set this field to the > + * respective DMA controller. > + * > + * Devices on USB and other peripheral busses also cannot perform > + * DMA by themselves. The @dma_dev field should point the bus > + * controller that does DMA on behalve of such a device. Required > + * for importing buffers via dma-buf. > + * > + * If set, the DRM core automatically releases the reference on the > + * device. > + */ > + struct device *dma_dev; > + > /** > * @managed: > * > @@ -327,4 +349,23 @@ struct drm_device { > struct dentry *debugfs_root; > }; > > +void drm_dev_set_dma_dev(struct drm_device *dev, struct device *dma_dev); > + > +/** > + * drm_dev_dma_dev - returns the DMA device for a DRM device > + * @dev: DRM device > + * > + * Returns the DMA device of the given DRM device. By default, this > + * the DRM device's parent. See drm_dev_set_dma_dev(). > + * > + * Returns: > + * A DMA-capable device for the DRM device. > + */ > +static inline struct device *drm_dev_dma_dev(struct drm_device *dev) > +{ > + if (dev->dma_dev) > + return dev->dma_dev; > + return dev->dev; > +} > + > #endif
On Fri, 7 Mar 2025 09:03:59 +0100, Thomas Zimmermann wrote: > 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. > > [ ... ] Reviewed-by: Maxime Ripard <mripard@kernel.org> Thanks! Maxime
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 bdb51c8f262e..ed4e5f06b79d 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -998,7 +998,7 @@ 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); diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h index 6ea54a578cda..e2f894f1b90a 100644 --- a/include/drm/drm_device.h +++ b/include/drm/drm_device.h @@ -64,6 +64,28 @@ struct drm_device { /** @dev: Device structure of bus-device */ struct device *dev; + /** + * @dma_dev: + * + * Device for DMA operations. Only required if the device @dev + * cannot perform DMA by itself. Should be NULL otherwise. Call + * drm_dev_dma_dev() to get the DMA device instead of using this + * field directly. Call drm_dev_set_dma_dev() to set this field. + * + * DRM devices are sometimes bound to virtual devices that cannot + * perform DMA by themselves. Drivers should set this field to the + * respective DMA controller. + * + * Devices on USB and other peripheral busses also cannot perform + * DMA by themselves. The @dma_dev field should point the bus + * controller that does DMA on behalve of such a device. Required + * for importing buffers via dma-buf. + * + * If set, the DRM core automatically releases the reference on the + * device. + */ + struct device *dma_dev; + /** * @managed: * @@ -327,4 +349,23 @@ struct drm_device { struct dentry *debugfs_root; }; +void drm_dev_set_dma_dev(struct drm_device *dev, struct device *dma_dev); + +/** + * drm_dev_dma_dev - returns the DMA device for a DRM device + * @dev: DRM device + * + * Returns the DMA device of the given DRM device. By default, this + * the DRM device's parent. See drm_dev_set_dma_dev(). + * + * Returns: + * A DMA-capable device for the DRM device. + */ +static inline struct device *drm_dev_dma_dev(struct drm_device *dev) +{ + if (dev->dma_dev) + return dev->dma_dev; + return dev->dev; +} + #endif
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 <tzimmermann@suse.de> --- drivers/gpu/drm/drm_drv.c | 21 +++++++++++++++++++ drivers/gpu/drm/drm_prime.c | 2 +- include/drm/drm_device.h | 41 +++++++++++++++++++++++++++++++++++++ 3 files changed, 63 insertions(+), 1 deletion(-)