linux-kernel - Aw: Re: [PATCH v3 10/13] arm64: dts: mediatek: mt7988a-bpi-r4: add gpio leds

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Message-ID: <trinity-4ce9e572-1086-4923-86e0-abaa27188e9b-1749638014100@trinity-msg-rest-gmx-gmx-live-b647dc579-v9bgf>
Date: Wed, 11 Jun 2025 10:33:34 +0000
From: Frank Wunderlich <frank-w@...lic-files.de>
To: angelogioacchino.delregno@...labora.com, linux@...web.de,
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Cc: jia-wei.chang@...iatek.com, johnson.wang@...iatek.com,
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Subject: Aw: Re: [PATCH v3 10/13] arm64: dts: mediatek: mt7988a-bpi-r4: add
 gpio leds

Hi
> Gesendet: Mittwoch, 11. Juni 2025 um 11:33
> Von: "AngeloGioacchino Del Regno" <angelogioacchino.delregno@...labora.com>
> Betreff: Re: [PATCH v3 10/13] arm64: dts: mediatek: mt7988a-bpi-r4: add gpio leds
>
> Il 08/06/25 23:14, Frank Wunderlich ha scritto:
> > From: Frank Wunderlich <frank-w@...lic-files.de>
> > 
> > Bananapi R4 has a green and a blue led which can be switched by gpio.
> > Green led is for running state so default on.
> > 
> > Green led also shares pin with eeprom writeprotect where led off allows
> > writing to eeprom.
> 
> This is extremely ugly from a hardware perspective and I'm sad to see such
> a thing here.

i know, but cannot change this...found this out while testing the eeprom...

where uboot allows the writing of eeprom currently without having this pin configured, linux does not and require green-led switch off.

> Though, I don't see any other solution, so I can only give you an advice:
> don't ever write to the eeprom from the kernel. Things will eventually go
> south otherwise.
> 
> I would also advise to add a read-only property to the eeprom node.

the eeprom is empty from factory, but can be used to store e.g. mac-adress which are random by default.

i tested a bit with tlv_eeprom command in uboot and some additional patches to archive this.

imho green-led as running indicator on (=write-protect of eeprom) is a good solution
=> readonly by default, but allowing to write it if user is really sure :)

> Regardless (and sadly),
> 
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Thanks for your opinion and RB

regards Frank