From: "Rafał Miłecki" <zajec5@gmail.com>
To: Michael Walle <michael@walle.cc>
Cc: devicetree@vger.kernel.org, hayashi.kunihiko@socionext.com,
krzysztof.kozlowski+dt@linaro.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
matthias.bgg@gmail.com, mhiramat@kernel.org, rafal@milecki.pl,
robh+dt@kernel.org, srinivas.kandagatla@linaro.org
Subject: Re: [PATCH 3/4] nvmem: mtk-efuse: replace driver with a generic MMIO one
Date: Wed, 1 Feb 2023 12:01:07 +0100 [thread overview]
Message-ID: <618392ed-7d20-a49f-1ec5-b27850d71dec@gmail.com> (raw)
In-Reply-To: <017a17eb99ac2b2c858d27b65c5dd372@walle.cc>
On 1.02.2023 11:46, Michael Walle wrote:
>> Before I convert brcm,nvram to NVMEM layout I need some binding & driver
>> providing MMIO device access. How to handle that?
>
> I'm not arguing against having the mmio nvmem driver. But I don't
> think we should sacrifice possible write access with other drivers. And
> I presume write access won't be possible with your generic driver as it
> probably isn't just a memcpy_toio().
>
> It is a great fallback for some nvmem peripherals which just maps a
> memory region, but doesn't replace a proper driver for an nvmem device.
OK, then maybe I'll retry again with generic MMIO and without converting
existing specific drivers. That is what (AFAIU) Rob asked though.
> What bothers me the most isn't the driver change. The driver can be
> resurrected once someone will do proper write access, but the generic
> "mediatek,efuse" compatible together with the comment above the older
> compatible string. These imply that you should use "mediatek,efuse",
> but we don't know if all mediatek efuse peripherals will be the
> same - esp. for writing which is usually more complex than the reading.
mediatek,efuse was already there, don't blame me for it ;)
> nitpick btw: why not "nvmem-mmio"?
Because I read from left to right ;)
It's MMIO based NVMEM. Not MMIO on top of NVMEM.
Sure, we have "nvmem-cells" but that is because those are cells of NVMEM
device.
Unless my English knowledge fails me.
> So it's either:
> (1) compatible = "mediatek,mt8173-efuse"
> (2) compatible = "mediatek,mt8173-efuse", "mmio-nvmem"
>
> (1) will be supported any anyway for older dts and you need to add
> the specific compatibles to the nvmem-mmio driver - or keep the
> driver as is.
>
> With (2) you wouldn't need to do that and the kernel can load the
> proper driver if available or fall back to the nvmem-mmio one. I'd
> even make that one "default y" so it will be available on future
> kernels and boards can already make use of the nvmem device even
> if there is no proper driver for them.
>
> I'd prefer (2). Dunno what the dt maintainers agree.
(2) looks OK, Rob, Krzysztof?
next prev parent reply other threads:[~2023-02-01 11:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 6:47 [PATCH 0/4] nvmem: add and use generic MMIO NVMEM Rafał Miłecki
2023-02-01 6:47 ` [PATCH 1/4] dt-bindings: nvmem: mmio: new binding for MMIO accessible NVMEM devices Rafał Miłecki
2023-02-03 21:06 ` Rob Herring
2023-02-01 6:47 ` [PATCH 2/4] nvmem: add generic driver for devices with MMIO access Rafał Miłecki
2023-02-01 9:41 ` Kunihiko Hayashi
2023-02-01 11:52 ` Srinivas Kandagatla
2023-02-02 9:24 ` AngeloGioacchino Del Regno
2023-02-01 6:47 ` [PATCH 3/4] nvmem: mtk-efuse: replace driver with a generic MMIO one Rafał Miłecki
2023-02-01 8:48 ` Michael Walle
2023-02-01 9:30 ` Rafał Miłecki
2023-02-01 10:46 ` Michael Walle
2023-02-01 11:01 ` Rafał Miłecki [this message]
2023-02-01 11:11 ` Michael Walle
2023-02-01 18:54 ` Rob Herring
2023-02-01 20:15 ` Michael Walle
2023-02-02 23:44 ` Rob Herring
2023-02-01 6:47 ` [PATCH 4/4] nvmem: uniphier-efuse: " Rafał Miłecki
2023-02-01 7:50 ` [PATCH 0/4] nvmem: add and use generic MMIO NVMEM Rafał Miłecki
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