Messages in this thread | | | From | Alistair Francis <> | Date | Tue, 17 Aug 2021 22:16:14 +1000 | Subject | Re: Revert "video: fbdev: mxsfb: Remove driver" |
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On Tue, Aug 17, 2021 at 8:03 PM Marek Vasut <marex@denx.de> wrote: > > On 8/17/21 11:08 AM, Alistair Francis wrote: > > On Mon, Aug 16, 2021 at 5:55 PM Marek Vasut <marex@denx.de> wrote: > >> > >> On 8/16/21 9:34 AM, Alistair Francis wrote: > >>> On Sun, Aug 15, 2021 at 10:31 PM Marek Vasut <marex@denx.de> wrote: > >>>> > >>>> On 8/15/21 2:16 PM, Alistair Francis wrote: > >>>>> Hello, > >>>>> > >>>>> Commit f225f1393f034 "video: fbdev: mxsfb: Remove driver" removed the > >>>>> mxsfb fbdev driver. > >>>>> > >>>>> I am now working on getting mainline Linux running on the reMarkable 2 > >>>>> eInk reader [1]. Unfortunately the rM2 doesn't use the standard EPD > >>>>> controller on the i.MX SoC, but instead uses the LCD controller. > >>>>> > >>>>> eInk panels are complex to control and require writing temperature > >>>>> dependent waveforms. As these waveforms are proprietary [2] the rM > >>>>> team runs closed source software called SWTCON in userspace to control > >>>>> the panel [3]. > >>>>> > >>>>> This closed source software expects the fbdev mxsfb driver and it > >>>>> doesn't work with the DRM mxsfb driver (at least not that I can get it > >>>>> to). > >>>>> > >>>>> The NXP fork of Linux also re-adds the fbdev driver [4], so they also > >>>>> see some uses for it. > >>>>> > >>>>> I was wondering if the community would be open to re-adding the fbdev > >>>>> mxsfb driver to mainline? It could be re-added with a different > >>>>> dt-binding so that it is not used by default and only enabled for > >>>>> boards when required (like for the rM2). > >>>>> > >>>>> 1: https://remarkable.com/store/remarkable-2 > >>>>> 2: https://goodereader.com/blog/e-paper/e-ink-waveforms-are-a-closely-guarded-secret > >>>>> 3: https://remarkablewiki.com/tech/rm2_framebuffer > >>>>> 4: https://source.codeaurora.org/external/imx/linux-imx/log/drivers/video/fbdev/mxsfb.c?h=lf-5.10.35-2.0.0 > >>>> > >>>> +CC Sam. > >>>> > >>>> What sort of special thing does your proprietary userspace do that > >>>> cannot be added to the DRM driver or the fbdev emulation (if needed) ? > >>> > >>> It's hard to tell. When using the DRM driver I get cryptic errors > >>> about the frame buffer not being available. > >> > >> Do you have fbdev emulation enabled ? Does /dev/fbX exist ? > > > > I do and /dev/fb0 exists > > > >> > >> What sort of messages do you get and from where ? > > > > This is the error I get: > > > > xochitl[252]: Error writing variable information: Invalid argument... > > Some ioctl returns -EINVAL maybe ? strace would tell you.
Ok, good progress. When xochitl works or doesn't work I see this for strace accesses:
``` openat(AT_FDCWD, "/dev/fb0", O_RDWR) = 5 ```
That's the only access for both the working case or the non-working case.
The actual application provides this log for the not working case (where it then hangs)
``` /usr/bin/xochitl --system 10:53.013 default 2021-06-11T11:42:05Z heads/releases/bertwhistle 264f47ba0 (int main(int, char**) /usr/src/debug/xochitl/override+gitAUTOINC+264f47ba03-r0/git/src/main.cpp:294) Registering exit handlers 10:53.018 default we're running on an epaper device (int main(int, char**) /usr/src/debug/xochitl/override+gitAUTOINC+264f47ba03-r0/git/src/main.cpp:301) Reading waveforms from /usr/share/remarkable/320_R349_AF0411_ED103TC2U2_VB3300-KCD_TC.wbf Error writing variable information: Invalid argument ```
These are the EINVAL strace tells me in the not working case:
prctl(PR_CAPBSET_READ, 0x30 /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, 0x2c /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, 0x2a /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, 0x29 /* CAP_??? */) = -1 EINVAL (Invalid argument) ioctl(5, FBIOPUT_VSCREENINFO, 0x4ce8e0) = -1 EINVAL (Invalid argument)
I'm guessing it's related to FBIOPUT_VSCREENINFO then, is that something that could be added to the DRM emulation?
> > > xochitl is the proprietary userspace code. I don't really have a good > > idea of what that error would mean. > > > > I also see this: > > > > Framebuffer has wrong id: "mxcfb" > > Are you sure you're not confusing mxcfb (The freescale imx scanout > engine) with mxsfb (The originally sgtl block, bought by freescale) ?
This is the full commit that gets everything working for me: https://github.com/alistair23/linux/commit/ee0e684e3d776c6de98b6491d1a87d8305c44734
It includes mxcfb, but I think that is just to allow the mxsfb to compile.
> > >> You could run strace on the application to see how it communicates with > >> the old driver via the ioctl interface and compare it with the fbdev > >> emulation on the new driver, maybe there is some odd ioctl which is not > >> emulated. > > > > I had a quick look at this. > > > > xochitl does a lot more than just controls the display, it interacts > > with lots of other hardware and strace produces a lot of logs. I also > > don't see the error when manually starting it, only at boot (but it > > still doesn't work). > > > > A quick run with > > > > strace -f xochitcl > > > > and I don't even see an access to /dev/fb0, so I'm not sure where the > > accesses are coming from. > > You can try writing the output of strace to file (strace -o) for easier > analysis. Then grep for either access to /dev/fb0 (or any symlink to it > which might exist), or search for the mxcfb string, maybe the > application aborts even before opening the fbdev due to some other problem.
Thanks, I figured out there was a script that I was running instead. I can now see the /dev/fb0 access.
Alistair
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