linux-kernel - Re: [PATCH 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

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Date:   Tue, 1 Feb 2022 11:36:48 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Maxime Ripard <maxime@...no.tech>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Lee Jones <lee.jones@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Linux PWM List <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED
 displays

Hello Geert,

On 2/1/22 09:43, Geert Uytterhoeven wrote:
> Hi Javier,
> 
> On Mon, Jan 31, 2022 at 9:12 PM Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>> This patch series adds a DRM driver for the Solomon OLED SSD1305, SSD1306,
>> SSD1307 and SSD1309 displays. It is a port of the ssd1307fb fbdev driver.
> 
> Thanks for your series!
> 
> I'll give it a try on an Adafruit FeatherWing 128x32 OLED, connected
> to an OrangeCrab ECP5 FPGA board running a 64 MHz VexRiscv RISC-V
> softcore.
>

Awesome! let me know if you have any issues. I keep an update-to-date version
at https://github.com/martinezjavier/linux/tree/ssd1307

>> Using the DRM fb emulation, all the tests from Geert Uytterhoeven's fbtest
>> (https://git.kernel.org/pub/scm/linux/kernel/git/geert/fbtest.git) passes:
>>
>>      ./fbtest -f /dev/fb1
>>     Using drawops cfb32 (32 bpp packed pixels)
>>     Available visuals:
>>       Monochrome
>>       Grayscale 256
>>       Truecolor 8:8:8:0
> 
> Oh, fake 32-bpp truecolor ;-)
>

Yes :) that's what the repaper drivers does to have maximum compatibility
with existing user-space and I followed the same.
 
> Does it run modetest, too?
>

It does, yes. And for example `modetest -M ssd1307` will print all the
info about encoders, connectors, CRTs, etc.
 
> I'm trying to get modetest working on my atari DRM driver.
> Comparing to the cirrus driver doesn't help much, as modetest doesn't
> seem to work with the cirrus driver (modified to not do hardware
> access, as I don't have cirrus hardware):
> 
>     # modetest -M cirrus -s 31:1024x768-60Hz
>     setting mode 1024x768-60.00Hz on connectors 31, crtc 34
>     failed to set gamma: Function not implemented
>

# modetest -M ssd1307 -c -s 31:128x64-0.12Hz
...
setting mode 128x64-0.12Hz on connectors 31, crtc 33
failed to set gamma: Function not implemented

this seems to be a bug in modetest. I found a patch posted some time ago
but never landed: https://www.spinics.net/lists/dri-devel/msg251356.html
 
> Does there exist another simple test program for showing something
> using the DRM API?
>

I tested with plymouth and gdm that make use of the DRM API, they do
start and I see something on the screen but don't really handle that
well the fact that's a 128x64 resolution.

I didn't test with more DRM programs because was mostly interested in
making sure that the fbdev emulation was working correctly.

Noticed that Simon shared some simple examples, I'll give them a try. 

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat