From: Maxime Ripard <maxime@cerno.tech>
To: Ralf Schlatterbeck <rsc@runtux.com>
Cc: Chen-Yu Tsai <wens@csie.org>, Mark Brown <broonie@kernel.org>,
linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org
Subject: Re: [PATCH] Fix SPI Chipselect/Clock bug for sun6i
Date: Fri, 8 Jan 2021 09:58:55 +0100 [thread overview]
Message-ID: <20210108085855.p255fioaax4zin4q@gilmour> (raw)
In-Reply-To: <20201226095845.c65lhsmluddvwxsl@runtux.com>
Hi,
On Sat, Dec 26, 2020 at 10:58:45AM +0100, Ralf Schlatterbeck wrote:
> This patch makes additional GPIOs usable as chipselects for SPI.
> It is available for years on the linux-sunxi SPIdev page at
> http://linux-sunxi.org/SPIdev and probably is originally by the user
> "Mirko" there. I've tried unsuccessfully to contact the author.
> Note that contrary to what is stated on the page above, the bug doesn't
> have cosmetic implications only:
>
> The SPI-Driver for the H2 Allwinner processor in the Linux kernel is
> supposed to support normal GPIOs as additional chipselects but fails to
> do so without the patch.
>
> For oscilloscope screenshots with/without the patch, see my blog post
> https://blog.runtux.com/posts/2019/04/18/
> or the discussion in the armbian forum at
> https://forum.armbian.com/topic/4330-spi-gpio-chip-select-support/
> (my logo there is a penguin).
> Please bear with me if I'm not following proper procedures, this is my
> first patch to the kernel in years.
>
> Thanks
> Ralf Schlatterbeck
>
> From 682ae1848b0df00cceb4c76486b971826b2737a9 Mon Sep 17 00:00:00 2001
> From: Ralf Schlatterbeck <rsc@runtux.com>
> Date: Thu, 11 Apr 2019 16:21:54 +0200
> Subject: [PATCH] Fix SPI Chipselect/Clock bug for sun6i
> Signed-off-by: Ralf Schlatterbeck <rsc@runtux.com>
>
> The current sun6i SPI implementation initializes the transfer too early,
> resulting in SCK going high before the transer. When using an additional
> (gpio) chipselect with sun6i, the chipselect is asserted at a time when
> clock is high, making the SPI transfer fail. This patch from the sunxi
> spidev page http://linux-sunxi.org/SPIdev fixes this, without the patch
> no additional gpio chipselects can be used. The relevant code seems to
> be from the user "Mirko" of the linux-sunxi wiki page, I was unable to
> contact the original author.
Unfortunately, without the author's Signed-off-by (and yours), we can't
merge that patch.
Maxime
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next prev parent reply other threads:[~2021-01-08 9:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-26 9:58 [PATCH] Fix SPI Chipselect/Clock bug for sun6i Ralf Schlatterbeck
2021-01-08 8:58 ` Maxime Ripard [this message]
2021-01-08 9:18 ` Ralf Schlatterbeck
2021-01-11 16:10 ` Maxime Ripard
2021-05-20 10:00 ` Ralf Schlatterbeck
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