linux-kernel - Re: [PATCH 3/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

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Message-ID: <3df2add7-6034-0527-825a-74e62e76dace@redhat.com>
Date:   Tue, 1 Feb 2022 15:36:04 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Noralf Trønnes <noralf@...nnes.org>,
        Maxime Ripard <maxime@...no.tech>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH 3/4] drm/tiny: Add driver for Solomon SSD1307 OLED
 displays

On 2/1/22 15:05, Geert Uytterhoeven wrote:
> Hi Javier,
> 
> On Tue, Feb 1, 2022 at 2:02 PM Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>> On 2/1/22 10:33, Thomas Zimmermann wrote:
>>>> +{
>>>> +    u8 col_end = col_start + cols - 1;
>>>> +    int ret;
>>>> +
>>>> +    if (col_start == ssd1307->col_start && col_end == ssd1307->col_end)
>>>> +            return 0;
>>>> +
>>>> +    ret = ssd1307_write_cmd(ssd1307->client, SSD1307_SET_COL_RANGE);
>>>> +    if (ret < 0)
>>>> +            return ret;
>>>> +
>>>> +    ret = ssd1307_write_cmd(ssd1307->client, col_start);
>>>> +    if (ret < 0)
>>>> +            return ret;
>>>> +
>>>> +    ret = ssd1307_write_cmd(ssd1307->client, col_end);
>>>> +    if (ret < 0)
>>>> +            return ret;
>>>
>>> Can you write these cmds in one step, such as setting up an array and
>>> sending it with ssd1307_write_array?
>>
>> I don't think so because the commands are different. But I'll check the
>> ssd1306 datasheet again to confirma that's the case.
> 
> IIRC, I tried that while working on the optimizations for ssd1307fb,
> and it didn't work.
>

That's what I would had expected by reading the datasheet. Thanks a
lot for confirming my assumption.
 

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