From: Robin Murphy <robin.murphy@arm.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Heiner Kallweit" <hkallweit1@gmail.com>,
"Rob Herring" <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski@canonical.com>,
"Andreas Färber" <afaerber@suse.de>,
"Miguel Ojeda" <ojeda@kernel.org>,
"linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"open list:ARM/Amlogic Meson..."
<linux-amlogic@lists.infradead.org>,
"Jerome Brunet" <jbrunet@baylibre.com>,
"Martin Blumenstingl" <martin.blumenstingl@googlemail.com>,
"Kevin Hilman" <khilman@baylibre.com>,
"Neil Armstrong" <narmstrong@baylibre.com>,
"Geert Uytterhoeven" <geert+renesas@glider.be>
Subject: Re: [PATCH v5 2/6] dt-bindings: auxdisplay: Add Titan Micro Electronics TM1628
Date: Tue, 19 Apr 2022 23:31:49 +0100 [thread overview]
Message-ID: <543820f8-5e93-eedb-e409-0cb13d092f07@arm.com> (raw)
In-Reply-To: <CAMuHMdV8iy4vMASuUgeQmjHdAMNzvCikwheyQO1-AQH0yYk0RQ@mail.gmail.com>
On 2022-03-21 08:12, Geert Uytterhoeven wrote:
> Hi Robin,
>
> On Fri, Mar 18, 2022 at 9:50 PM Robin Murphy <robin.murphy@arm.com> wrote:
>> On 2022-02-25 21:13, Heiner Kallweit wrote:
>>> Add a YAML schema binding for TM1628 auxdisplay
>>> (7/11-segment LED) controller.
>>>
>>> This patch is partially based on previous work from
>>> Andreas Färber <afaerber@suse.de>.
>>>
>>> Co-developed-by: Andreas Färber <afaerber@suse.de>
>>> Signed-off-by: Andreas Färber <afaerber@suse.de>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/auxdisplay/titanmec,tm1628.yaml
>
>>> +
>>> +patternProperties:
>>> + "^.*@[1-7],([1-9]|1[0-6])$":
>>> + type: object
>>> + $ref: /schemas/leds/common.yaml#
>>> + unevaluatedProperties: false
>>> + description: |
>>> + Properties for a single LED.
>>> +
>>> + properties:
>>> + reg:
>>> + description: |
>>> + 1-based grid number, followed by 1-based segment bit number.
>>> + maxItems: 1
>>> +
>>> + required:
>>> + - reg
>>
>> I'm concerned that this leaves us no room to support the additional
>> keypad functionality in future. Having now double-checked a datasheet,
>> the inputs are also a two-dimensional mux (sharing the segment lines),
>> so the device effectively has two distinct but numerically-overlapping
>> child address spaces - one addressed by (grid,segment) and the other by
>> (segment,key).
>
> Sounds similar to HT16K33?
/me searches up a datasheet...
Keypad-wise, it appears so, however the display side of this
1618/1628/1638 family is very much tuned for 7-segment displays rather
than arbitrary dot-matrix ones.
I do recall when I was digging a few years ago, turning up an old Holtek
VFD driver which looked suspiciously like it might be the origin of the
particular 3-wire protocol and command set (including weird non-linear
brightness scale) which all these LED driver clones seem to borrow from,
but I can't now remember the part number :(
>> Rob, Krysztof, any thoughts on the best DT idiom to leave accommodation
>> for that? I'm thinking either require an intermediate node to contain
>> each notional address space, or perhaps add another leading address cell
>> to select between them? I don't believe any of these things have further
>> functionality beyond that.
>
> The problem with these devices is that there are thousands of different
> ways to wire them, and coming up with a generic wiring description in
> DT and writing code to handle that can be very hard.
>
> For HT16K33 non-dot-matrix wirings, I just added extra compatible
> values matching the wiring of a few known devices[1]. That way the
> driver can handle them efficiently.
> It does have the disadvantage that adding support for new devices
> means introducing more compatible values, and adding more code.
>
> Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml
I think the display side of Heiner's binding is fine for what these
chips can do - I've finally had a bit more time to play with this
series, and (with minor driver hacks) it works just fine to describe my
TM1638 breakout board with an 8-digit display, where segments 8 and 9 of
each grid are respectively a decimal point and a discrete indicator LED,
managed as separate LED nodes.
However, I think you've indirectly addressed my outstanding concern
there - I wasn't aware of the "linux,keymap" property, but since that
brings its own implicit (row,column) addresses distinct from the DT
address space, it looks like that might be sufficient as a neat standard
way to extend this binding in future *without* any other changes.
Thanks,
Robin.
next prev parent reply other threads:[~2022-04-19 22:32 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 21:09 [PATCH v5 0/6] auxdisplay: Add support for the Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-02-25 21:10 ` [PATCH v5 1/6] dt-bindings: vendor-prefixes: Add Titan Micro Electronics Heiner Kallweit
2022-02-25 21:13 ` [PATCH v5 2/6] dt-bindings: auxdisplay: Add Titan Micro Electronics TM1628 Heiner Kallweit
2022-03-04 23:07 ` Rob Herring
2022-03-18 20:50 ` Robin Murphy
2022-03-21 8:12 ` Geert Uytterhoeven
2022-04-19 22:31 ` Robin Murphy [this message]
2022-03-21 8:34 ` Krzysztof Kozlowski
2022-03-23 20:33 ` Heiner Kallweit
2022-03-30 5:54 ` Heiner Kallweit
2022-04-19 23:04 ` Robin Murphy
2022-04-20 16:27 ` Heiner Kallweit
2022-03-21 8:28 ` Krzysztof Kozlowski
2022-02-25 21:16 ` [PATCH v5 3/6] docs: ABI: document tm1628 attribute display_text Heiner Kallweit
2022-02-25 21:20 ` [PATCH v5 4/6] auxdisplay: add support for Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-02-25 21:22 ` [PATCH v5 5/6] arm64: dts: meson-gxl-s905w-tx3-mini: add support for the 7 segment display Heiner Kallweit
2022-02-25 21:22 ` [PATCH v5 6/6] MAINTAINERS: Add entry for tm1628 auxdisplay driver Heiner Kallweit
2022-03-08 18:32 ` [PATCH v5 0/6] auxdisplay: Add support for the Titanmec TM1628 7 segment display controller Heiner Kallweit
2022-03-16 0:38 ` Robin Murphy
2022-03-16 21:19 ` Heiner Kallweit
2022-03-17 20:08 ` Robin Murphy
2022-03-17 21:49 ` Heiner Kallweit
2022-03-18 20:13 ` Robin Murphy
2022-04-23 20:57 ` Miguel Ojeda
2022-04-24 9:06 ` Heiner Kallweit
2022-05-12 12:46 ` Robin Murphy
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