linux-kernel - Re: [PATCH v3 3/7] drm: Add driver for Solomon SSD130X OLED displays

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Message-ID: <fb8d6519-2db0-3b94-61ca-2081a6b2e3a4@redhat.com>
Date:   Fri, 11 Feb 2022 09:54:55 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Noralf Trønnes <noralf@...nnes.org>,
        Maxime Ripard <maxime@...no.tech>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-fbdev@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.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>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3 3/7] drm: Add driver for Solomon SSD130X OLED displays

On 2/9/22 17:26, Javier Martinez Canillas wrote:
> On 2/9/22 17:08, Andy Shevchenko wrote:
> 
> [snip]
> 
>>> Agreed, as mentioned I'll give it a try to sending all the data as a
>>> bulk write with regmap.
>>
>> Ah, it might be that it should be noinc bulk op. Need to be checked anyway.
>>
> 
> Yeah, I'll give it a try for v4. Let's see how it goes.
> 

I tried to do bulk writes for the command, but the problem is that the
command stream has to be as follow (i.e: SSD130X_SET_COL_RANGE command):

SSD130X_COMMAND
SSD130X_SET_COL_RANGE
SSD130X_COMMAND
col_start
SSD130X_COMMAND
col_end

That is, a SSD130X_COMMAND has to be writtn for each command and command
option. This means that you need to either construct a command stream in
the ssd130x_write_cmd() function or pass multiple SSD130X_COMMAND as
variadic arguments.

Both cases lead to a less elegant implementation than just having a count
parameter in ssd130x_write_cmd() and doing multiple writes as it is done
in the current implementation.

After all, these are only for commands that are done once to setup the
device. The SSD130X_DATA writes that are to update the display pixels are
already done in bulk, which are more important to do it efficiently.

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