On 15.03.2025 00:50, Alex Lanzano wrote: > On Fri, Mar 14, 2025 at 12:57:27PM +0100, Josef Luštický wrote: >> On Mon, Mar 10, 2025 at 7:33 PM Alex Lanzano <lanzano.alex@xxxxxxxxx> wrote: >>> >>> On Fri, Mar 07, 2025 at 10:25:18AM +0100, Josef Luštický wrote: >>>> Ok, I'll implement the change and post it for a review. >>>> About the property naming, I tend to name it something like >>>> "inverted-reset-gpio-fixed" to denote that it is assumed the code >>>> using the "reset-gpios" property was fixed. >>>> What are your thoughts? >>>> >>> >>> You probably wnat something more concise and in present tense like >>> 'invert-reset-gpio' >> >> OK, I understand. >> It still feels like the 'invert' would mean that the code is supposed >> to do something non-standard with the reset-gpios property >> specification. >> How about 'correct-reset-gpio' or 'proper-reset-gpio' to denote that >> the reset-gpio property describes the HW correctly. >> > > My main concern here is that the device tree properties are supposed to > be completely independent of the driver code. So, I'd be hesitant to > imply that a property 'fixes' a specific behavior in the driver in the > name of the property itself (even though it does). > I suggest you ask on the devicetree ML, they probably know how to handle bugs like this. Noralf. > Best regards, > Alex > >>>> On Tue, Feb 25, 2025 at 2:46 PM Alex Lanzano <lanzano.alex@xxxxxxxxx> wrote: >>>>> >>>>> On Tue, Feb 25, 2025 at 12:59:59PM +0100, Josef Luštický wrote: >>>>>> On Mon, Feb 24, 2025 at 12:13 AM Alex Lanzano <lanzano.alex@xxxxxxxxx> wrote: >>>>>>> >>>>>>> On Mon, Feb 17, 2025 at 12:39:01PM +0100, Josef Luštický wrote: >>>>>>>> On Sat, Feb 15, 2025 at 8:14 PM Alex Lanzano <lanzano.alex@xxxxxxxxx> wrote: >>>>>>>>> >>>>>>>>> On Fri, Feb 14, 2025 at 08:04:41PM -0500, Alex Lanzano wrote: >>>>>>>>>> On Fri, Feb 14, 2025 at 10:29:29AM +0100, Josef Luštický wrote: >>>>>>>>>>> Hello Alex, >>>>>>>>>>> there is a bug in mipi_dbi_hw_reset() function that implements the logic of >>>>>>>>>>> display reset contrary. >>>>>>>>>>> It keeps the reset line activated which keeps displays in reset state. >>>>>>>>>>> >>>>>>>>>>> I reported the bug to >>>>>>>>>>> https://gitlab.freedesktop.org/drm/misc/kernel/-/issues/63 >>>>>>>>>>> >>>>>>>>>>> Unfortunately, fixing the bug would mean current DTB-ABI breakage and >>>>>>>>>>> device-trees modification would be needed. >>>>>>>>>>> I mainly write this email to let you and other people know about it, so >>>>>>>>>>> hopefully it can be found easier. >>>>>>>>>>> What are your thoughts? >>>>>>>>>> Thanks for making me aware. I'll dig into over the weekend and get back >>>>>>>>>> to you >>>>>>>>> >>>>>>>>> Alright so I looked into a bit more. Looks like the MIPI Specification >>>>>>>>> says that the reset line is active low. So, if we want dt entries to be >>>>>>>>> correct the logic for setting the reset line in mipi_dbi_hw_reset() >>>>>>>>> should be flipped. However, like you said, this is going to cause a some >>>>>>>>> confused developers to break out their oscilloscopes to figure out >>>>>>>>> why their display isn't working. >>>>>>>>> >>>>>>>>> Best regards, >>>>>>>>> Alex >>>>>>>> >>>>>>>> Thank you Alex for looking into this. >>>>>>>> I think all the supported dts can be changed together with >>>>>>>> mipi_dbi_hw_reset(), however the fix would break existing DTBs and >>>>>>>> third party DTSs. >>>>>>>> So I think it shall be either noted somewhere that due to this bug, >>>>>>>> the reset line needs to be "wrongly" ACTIVE_HIGH in DTS >>>>>>>> or the mipi_dbi_hw_reset() is changed and the compatibility is broken, >>>>>>>> which needs to be announced. >>>>>>>> >>>>>>>> BTW Zephyr fixed the code [1], but they introduced the MIPI DBI >>>>>>>> support just a couple of weeks before the fix, so they avoided the >>>>>>>> compatibility issue. >>>>>>>> I was not able to find users mentioning issues related to the display >>>>>>>> not functioning properly, so I had to dig into the code. >>>>>>>> But afterwards I found a thread on Raspberry PI forums, where one of >>>>>>>> the moderators mentions it [2]. >>>>>>>> >>>>>>>> [1] https://github.com/zephyrproject-rtos/zephyr/issues/68562 >>>>>>>> [2] https://forums.raspberrypi.com/viewtopic.php?p=2165720#p2165720 >>>>>>> >>>>>>> So, here are my thoughts on this after pondering it over for a bit. >>>>>>> Ideally we should eventually reverse the reset logic so the DTS entry >>>>>>> correctly specifies the hardware. However, instead of an abrupt change >>>>>>> maybe we add an additional property to the DTS node that when present >>>>>>> uses the correct reset logic. If the property isn't present we use the >>>>>>> current incorrect reset logic and print out a dev_warn that it will soon >>>>>>> be deprecated. >>>>>>> >>>>>>> Let me know what you think. >>>>>>> >>>>>>> Best regards, >>>>>>> Alex >>>>>>> >>>>>>> >>>>>> I think it's a good idea if the current logic is about to be fixed. >>>>>> Another (probably not as good) idea is to introduce a new property >>>>>> named "nreset-gpios = ..." or something like that, but I realise that >>>>>> "reset-gpios" is the de-facto standard naming. >>>>>> >>>>>> Best regards, >>>>>> Josef >>>>>> >>>>> >>>>> Yeah I think it may be simpler to just add a boolean property like >>>>> 'reverse-reset'. It would make the driver code simpler to implement too. >>>>> Would you like to implement this change and submit the patch or would >>>>> you like me to? >>>>> >>>>> Best regards, >>>>> Alex
