Hi, Eizan: Eizan Miyamoto <eizan@xxxxxxxxxxxx> 於 2020年5月6日 週三 下午4:41寫道： > > Broadly, this patch (1) adds a driver for various MTK MDP components to > go alongside the main MTK MDP driver, and (2) hooks them all together > using the component framework. > > (1) Up until now, the MTK MDP driver controls 8 devices in the device > tree on its own. When running tests for the hardware video decoder, we > found that the iommus and LARBs were not being properly configured. To > configure them, a driver for each be added to mtk_mdp_comp so that > mtk_iommu_add_device() can (eventually) be called from dma_configure() > inside really_probe(). > > (2) The integration into the component framework allows us to defer the > registration with the v4l2 subsystem until all the MDP-related devices > have been probed, so that the relevant device node does not become > available until initialization of all the components is complete. > > Some notes about how the component framework has been integrated: > > - The driver for the rdma0 component serves double duty as the "master" > (aggregate) driver as well as a component driver. This is a non-ideal > compromise until a better solution is developed. This device is > differentiated from the rest by checking for a "mediatek,vpu" property > in the device node. > > - The list of mdp components remains hard-coded as mtk_mdp_comp_dt_ids[] > in mtk_mdp_core.c, and as mtk_mdp_comp_driver_dt_match[] in > mtk_mdp_comp.c. This unfortunate duplication of information is > addressed in a following patch in this series. > > - The component driver calls component_add() for each device that is > probed. > > - In mtk_mdp_probe (the "master" device), we scan the device tree for > any matching nodes against mtk_mdp_comp_dt_ids, and add component > matches for them. The match criteria is a matching device node > pointer. > > - When the set of components devices that have been probed corresponds > with the list that is generated by the "master", the callback to > mtk_mdp_master_bind() is made, which then calls the component bind > functions. > > - Inside mtk_mdp_master_bind(), once all the component bind functions > have been called, we can then register our device to the v4l2 > subsystem. > > - The call to pm_runtime_enable() in the master device is called after > all the components have been registered by their bind() functions > called by mtk_mtp_master_bind(). As a result, the list of components > will not change while power management callbacks mtk_mdp_suspend()/ > resume() are accessing the list of components. For the component binding problem, MDP is similar to DRM driver [1], and DRM is probed by mmsys driver [2] (mmsys is a device which control display clock, display routing, mdp clock, mdp routing). Maybe you could refer to what DRM does. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/mediatek/mtk_drm_drv.c?h=v5.8-rc6 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.8-rc6&id=667c769246b01c53ad0925d603d2a2531abd3ef2 Regards, Chun-Kuang. > > Signed-off-by: Eizan Miyamoto <eizan@xxxxxxxxxxxx>
