On 29.06.2017 17:22, Eric Anholt wrote: > Andrzej Hajda <a.hajda@xxxxxxxxxxx> writes: > >> On 29.06.2017 07:03, Archit Taneja wrote: >>> On 06/28/2017 01:28 AM, Eric Anholt wrote: >>>> When a mipi_dsi_host is registered, the DT is walked to find any child >>>> nodes with compatible strings. Those get registered as DSI devices, >>>> and most DSI panel drivers are mipi_dsi_drivers that attach to those nodes. >>>> >>>> There is one special case currently, the adv7533 bridge, where the >>>> bridge probes on I2C, and during the bridge attach step it looks up >>>> the mipi_dsi_host and registers the mipi_dsi_device (for its own stub >>>> mipi_dsi_driver). >>>> >>>> For the Raspberry Pi panel, though, we also need to attach on I2C (our >>>> control bus), but don't have a bridge driver. The lack of a bridge's >>>> attach() step like adv7533 uses means that we aren't able to delay the >>>> mipi_dsi_device creation until the mipi_dsi_host is present. >>>> >>>> To fix this, we extend mipi_dsi_device_register_full() to allow being >>>> called with a NULL host, which puts the device on a queue waiting for >>>> a host to appear. When a new host is registered, we fill in the host >>>> value and finish the device creation process. >>> This is quite a nice idea. The only bothering thing is the info.of_node usage >>> varies between child nodes (mipi_dsi_devs) and non-child nodes (i2c control >>> bus). >>> >>> For DSI children expressed in DT, the of_node in info holds the DT node >>> corresponding to the DSI child itself. For non-DT ones, this patch assumes >>> that info.of_node stores the DSI host DT node. I think it should be okay as >>> long as we mention the usage in a comment somewhere. The other option is to >>> have a new info.host_node field to keep a track of the host DT node. >> Field abuse is not a biggest issue. >> >> This patch changes totally semantic of mipi_dsi_device_register_full. >> Currently semantic of *_device_register* function is to create and add >> device to existing bus, ie after return we have device attached to bus, >> so it can be instantly used. With this change function can return some >> unattached device, without warranty it will be ever attached - kind of >> hidden deferring. Such change looks for me quite dangerous, even if it >> looks convenient in this case. > It only changes the semantic if you past in a NULL host, from "oops" to > "do something useful". > >> As discussed in other thread more appealing solution for me would be: >> 1. host creates dsi bus, but doesn't call component_add as it does not >> have all required resources. >> 2. host waits for all required dsi devs attached, gets registered panels >> or bridges and calls component_add after that. >> 3. in bind phase it has all it needs, hasn't it? >> >> I did not spent much time on this idea, so I cannot guarantee it has not >> fundamental issues :) > If component_add() isn't called during probe, then DSI would just get > skipped during bind as far as I know. No, drm master will wait till all components are present. > > I *think* what you're thinking is moving DSI host register to probe, yes, this way you will allow to create dsi devices. > and > then panel lookup stays in bind. no, panel lookup will be performed in dsi_host attach callback, and component_add will be called also there, if all required panels/bridges are get. > That seems much more risky to me -- do > we know for sure that no mipi_dsi_device will do any DSI transactions > during its probe? I would expect some of them to. I think it is irrelevant, with the current design only transactions between prepare/unprepare callbacks have chances to succeed. Andrzej _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
