Hello On Tue, Mar 14, 2023 at 01:59:06PM +0100, Francesco Dolcini wrote: > +Marco > > On Tue, Mar 14, 2023 at 02:45:53PM +0200, Sakari Ailus wrote: > > On Tue, Mar 14, 2023 at 01:32:16PM +0100, Francesco Dolcini wrote: > > > On Tue, Mar 14, 2023 at 02:13:46PM +0200, Sakari Ailus wrote: > > > > On Mon, Mar 06, 2023 at 07:36:49AM +0100, Marcel Ziswiler wrote: > > > > > From: Aishwarya Kothari <aishwarya.kothari@xxxxxxxxxxx> > > > > > > > > > > Implement the introduced get_mbus_config operation to report the > > > > > config of the MIPI CSI-2, BT.656 and Parallel interface. > > > > > > > > > > Signed-off-by: Aishwarya Kothari <aishwarya.kothari@xxxxxxxxxxx> > > > > > Signed-off-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx> > > > > > > > > What's the reasoning for this patch? > > > > > > Without this it's not possible to use it on i.MX6, > > > drivers/staging/media/imx/imx6-mipi-csi2.c requires it, some more > > > details from Jacopo here [0]. > > > > > > Everything used to work fine up to v5.18, after that kernel version > > > various changes broke it [1][2] (I assume you are pretty much aware of > > > the history here, you commented on a few emails). > > > > > > [0] https://lore.kernel.org/all/20230128100611.7ulsfqqqgscg54gy@uno.localdomain/ > > > [1] https://lore.kernel.org/all/081cc2d3-1f3a-6c14-6dc7-53f976be7b2b@xxxxxxxxx/ > > > [2] https://lore.kernel.org/all/cacfe146-101b-35b3-5f66-1a1cabfd342f@xxxxxxxxx/ > > > > > > > Drivers that don't have e.g. dynamic lane configuration shouldn't need to > > > > implement get_mbus_config. > > > > Not even for staging drivers. The driver should be fixed to get that > > information from the endpoint instead. > > This seems exactly the opposite of what commit > 7318abface48 ("media: imx: Use get_mbus_config instead of parsing upstream DT endpoints") > did. > > Given that I am somehow confused, but I am not that familiar with this > subsystem, so I guess this is expected :-). Can someone provide some > additional hint here? > As per my understanding, the i.MX6 IPU CSI driver connects to the CSI-2 receiver and/or two video muxes. One figure's worth a thousands words: "Figure 19-1. CSI2IPU gasket connectivity" of the IMX6DQRM TRM. So the local endpoint might not provide the required information on the bus configuration as it connects to a video-mux. That's why the imx_media_pipeline_subdev() helper is used in csi_get_upstream_mbus_config(). My gut feeling is that it would be better to always call get_mbus_config() on the next subdev (the mux or the CSI-2 rx) and there parse the local endpoint as it's the mux or the CSI-2 rx that connect to the actual source. To be honest my understanding is that this patch has always been needed to work on imx6 and this is not a regression but something that was kept as an out-of-tree patch downstream. Is this correct or is this a regression ? The above mentioned patches that move fwnode matching to endpoints don't seem related, don't they ? Thanks j > > I don't object having a helper in the framework to do this though. There > > are many receiver drivers that need this to work with those devices that > > have variable number of lanes. > > Thanks in advance, > Francesco >
