On Sun, Mar 16, 2025 at 12:51:29PM +0100, Krzysztof Kozlowski wrote: > On 15/03/2025 16:20, Alex Lanzano wrote: > > Hi all, > > > > There is a bug in the mipi_dbi_hw_reset() function that handles the > > reset logic of the controller. Currently, it will set the reset gpio > > value to 0, wait a specified time, then set the reset gpio value to 1. > > > > The issue with this implementation is that the MIPI DBI spec states that > > the reset signal is active low. So, in order to correct for this logic, > > the developer needs to incorrectly define the reset gpio as active high > > in the DT. > > You should address it to driver and subsystem maintainers. Instead you > skipped all maintainers but Cc-ed people who have nothing to do with > MIPI DBI drivers in the kernel. > My apologies. I wanted to get the advice from you and the other device tree maintainers since I was proposing a new device property to address this issue. CC'ing them on the thread now. > > > > Fixing the logic in the driver would cause all the displays using this > > driver downstream to stop working. To mitigate this, Josef and I were > > thinking about adding an additional boolean property to the DT that when > > present would use the correct reset logic in the driver. And if it's not > > present use the current reset logic and print out a warning that this > > reset logic is deprecated. > > > > The overall plan would be to have this temporary fix for a few release > > cycles so downstream has time to be aware of the issue and update their > > DT. Eventually, we would remove the incorrect reset logic in the driver > > and this addtional boolean property. > > That's an ABI now, so you cannot change it without affecting users. Code > is from 2018 so you have plenty of users now. > > I did some workaround for wsa88xx speakers but that's an exception and > it should not necessarily be a pattern to follow. > > Not sure if it the issue is worth changing considering the impact. > Makes sense, I'm just a bit concerned about the device tree definitions not being compatible across different platforms. Best regards, Alex
