On Tue, Jan 31, 2023 at 7:29 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > On Tue, Jan 31, 2023 at 07:17:50PM +0530, Jagan Teki wrote: > > On Tue, Jan 31, 2023 at 6:16 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > > > > > On Mon, Jan 30, 2023 at 06:54:54PM +0530, Jagan Teki wrote: > > > > On Mon, Jan 30, 2023 at 6:26 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > > > > > > > > > On Fri, Jan 27, 2023 at 11:09:26PM +0530, Jagan Teki wrote: > > > > > > Hi, > > > > > > > > > > > > On Thu, Jan 26, 2023 at 8:48 PM Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > On Thu, Jan 26, 2023 at 5:42 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > On Mon, Jan 23, 2023 at 08:41:56PM +0530, Jagan Teki wrote: > > > > > > > > > Add devm OF helper to return the next DSI bridge in the chain. > > > > > > > > > > > > > > > > > > Unlike general bridge return helper devm_drm_of_get_bridge, this > > > > > > > > > helper uses the dsi specific panel_or_bridge helper to find the > > > > > > > > > next DSI device in the pipeline. > > > > > > > > > > > > > > > > > > Helper lookup a given child DSI node or a DT node's port and > > > > > > > > > endpoint number, find the connected node and return either > > > > > > > > > the associated struct drm_panel or drm_bridge device. > > > > > > > > > > > > > > > > I'm not sure that using a device managed helper is the right choice > > > > > > > > here. The bridge will stay longer than the backing device so it will > > > > > > > > create a use-after-free. You should probably use a DRM-managed action > > > > > > > > here instead. > > > > > > > > > > > > > > Thanks for the comments. If I understand correctly we can use > > > > > > > drmm_panel_bridge_add instead devm_drm_panel_bridge_add once we found > > > > > > > the panel or bridge - am I correct? > > > > > > > > > > > > Look like it is not possible to use DRM-managed action helper here as > > > > > > devm_drm_of_dsi_get_bridge is calling from the DSI host attach hook in > > > > > > which we cannot find drm_device pointer (as drm_device pointer is > > > > > > mandatory for using DRM-managed action). > > > > > > https://github.com/openedev/kernel/blob/imx8mm-dsi-v12/drivers/gpu/drm/bridge/samsung-dsim.c#L1545 > > > > > > > > > > > > Please check and correct me if I mentioned any incorrect details. > > > > > > > > > > You shouldn't call that function from attach anyway: > > > > > https://dri.freedesktop.org/docs/drm/gpu/drm-kms-helpers.html#special-care-with-mipi-dsi-bridges > > > > > > > > True, If I remember we have bridges earlier to find the downstream > > > > bridge/panels from the bridge ops and attach the hook, if that is the > > > > case maybe we can use this DRM-managed action as we can get the > > > > drm_device pointer from the bridge pointer. > > > > > > I'm not quite sure what you mean. You shouldn't retrieve the bridge from > > > the attach hook but from the probe / bind ones. If that's not working > > > for you, this is a bug in the documentation we should address. > > > > Something like this, afterward the design has updated to move the > > panel or bridge found to be in host attach. > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/bridge/nwl-dsi.c?h=v5.10#n911 > > What are you pointing to exactly, it's not a MIPI-DSI host attach, > that's a bridge attach, you have access to the DRM device there. Yes, what I'm saying here is we can have the option to use a DRM device pointer so finding the panel or bridge by using a DRM-managed action helper can be possible rather than host attach. Something like this, struct drm_bridge *drmm_of_dsi_get_bridge(struct drm_device *drm, struct device_node *np, u32 port, u32 endpoint) { struct drm_bridge *bridge; struct drm_panel *panel; int ret; ret = drm_of_dsi_find_panel_or_bridge(np, port, endpoint, &panel, &bridge); if (ret) return ERR_PTR(ret); if (panel) bridge = drmm_panel_bridge_add(drm, panel); return bridge; } static int nwl_dsi_bridge_attach(struct drm_bridge *bridge, enum drm_bridge_attach_flags flags) { struct nwl_dsi *dsi = bridge_to_dsi(bridge); struct drm_bridge *bridge; int ret; bridge = drmm_of_dsi_get_bridge(bridge->dev, dsi->dev->of_node, 1, 0); if (IS_ERR(bridge)) ret = PTR_ERR(dsi->out_bridge); return drm_bridge_attach(bridge->encoder, dsi->panel_bridge, bridge, flags); } static const struct drm_bridge_funcs nwl_dsi_bridge_funcs = { .attach = nwl_dsi_bridge_attach, }; > > > > > > > > So, what is the best we can do here, add any TODO comment to follow up > > > > the same in the future or something else, please let me know? > > > > > > Make it work in a safe way, as described in the documentation? > > > > Yeah, it is a clear deadlock. It is not possible to use DM-managed > > action helper in host attach as there is no drm_device pointer and we > > cannot move panel or bridge finding out of host attach as per design > > documentation. I'm thinking of go-ahead with adding TODO for adding > > the safe way with an existing patch. Please let me know. > > I've been telling you for three mails now that it's not acceptable. So, > again, no, it's not acceptable. Do something else and follow the > documentation instead. Ohh, look like I didn't get this in the first e-mail. Okay, now I got it, thanks. On the other hand, this series recurring for more than a year, so to merge things go quickly can you please suggest some solution based on this discussion? Thanks, Jagan.
