Re: [PATCH 03/16] staging: m57621-mmc: delete driver from the tree.

From: NeilBrown <neil@brown.name>
To: "Christian Lütke-Stetzkamp" <christian@lkamp.de>
Cc: George Hilliard <thirtythreeforty@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	devel@driverdev.osuosl.org,
	Nishad Kamdar <nishadkamdar@gmail.com>,
	linux-kernel@vger.kernel.org,
	Sergej Perschin <ser.perschin@gmail.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	John Crispin <blogic@openwrt.org>
Subject: Re: [PATCH 03/16] staging: m57621-mmc: delete driver from the tree.
Date: Wed, 03 Apr 2019 10:57:38 +1100	[thread overview]
Message-ID: <87imvw0xl9.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20190402204658.GA5187@habor.localdomain>

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On Tue, Apr 02 2019, Christian Lütke-Stetzkamp wrote:

> On Wed, Apr 03, 2019 at 06:51:49AM +1100, NeilBrown wrote:
>> People keep telling me that drivers/mmc/host/mtk-sd.c should be able to
>> handle the same hardware as this driver, with a little bit of work.
>> Unfortunately they haven't told me what the little bit of work involves.
>> 
>> Have you explored that possibility at all?  I might try to have a look
>> if I can make time.
>
> I have started to look into it, when I was working on that
> driver. First sorry for me doing nothing in the last few
> month. Generally the two drivers seem to be very similar, the main
> difference is the code for tuning. In the staging driver. this is a
> total mess. It tries to account for tuning itself, so it also tries to
> account which command was executed (succesfully) before a tuning is
> necessary and reexecutes it, when it was the APP_CMD. But there are
> still some differences in the tuning code, that are not due to
> handling it in the driver.
>
> If have mainly understand how to remove the 'in driver handling' of
> the tuning and thing I could prepare a patch for that. But the
> differences in the tuning code itself, I do not understand
> completely.
>
> There are two other larger differences that I found during my
> work. One is that drivers/mmc/host/mtk-sd.c has much more features,
> like voltage and clock handling and some support for high speed
> modes. I don't know if these features are required/useful for this
> device. The other thing is the card detect handling. This driver is
> doing the card detect / read only detection on its own, where the in
> tree one just uses some default gpio functions there and I don't know
> weather this must be changed or weather there is a gpio driver for the
> mt7621.
>
> That is all I currently remember. Hope it helps.
>
> Christian

Thanks, it might be.
Other info I have received at
   https://github.com/gnubee-git/GnuBee_Docs/issues/75#issuecomment-479216537

is that there might be something worth examining at

 https://github.com/jonpry/openwrt_mt7688/commit/a85e6d99899f3dc1204cd5bfba944e17bfa6178f
 https://github.com/jonpry/openwrt_mt7688/commit/24878467a650d765b747618de1a575e79114b764

        A few notes: The MMC driver there is basically the 4.9 mtk-sd
        one with all the patches from maybe 4.17 or 4.18 backported.

and that a diff against current mainline here:

  https://gist.github.com/neheb/3d9e4cbf966f8487114df19b49f28214

might be useful.

I'll look more on the weekend if no-one beats me to it.

NeilBrown

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