Re: [PATCH 0/6] Fix R-Car I2C data byte sent twice issue

From: Wolfram Sang <wsa@the-dreams.de>
To: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-i2c@vger.kernel.org,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	Biju Das <biju.das@bp.renesas.com>,
	stable@vger.kernel.org,
	Ben Hutchings <ben.hutchings@codethink.co.uk>
Subject: Re: [PATCH 0/6] Fix R-Car I2C data byte sent twice issue
Date: Tue, 29 May 2018 19:19:58 +0200	[thread overview]
Message-ID: <20180529171957.y2ctsptsnjw6ykag@ninjato> (raw)
In-Reply-To: <1527600796-25901-1-git-send-email-fabrizio.castro@bp.renesas.com>

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> this series fixes an issue with the I2C driver of the Renesas R-Car and
> RZ/G1 family of chips. The issue is clearly visible with the CIP kernel
> (4.4) running on a iwg20d board from iWave due to the way the bq32000
> driver/device is interacting with the I2C driver/controller.
> In the stable kernel (4.4) there is no support for the iwg20d, I tried
> to replicate the same problem on a Koelsch board with no success, but
> the problem is there.

For the record, this patchset was developed on a Lager board (R-Car H2)
but the issue was known to be present on other Gen2 SoCs, too. This was
a nasty race condition. IIRC I was able to reproduce the issue only with
the first transfer after boot (for whatever reason). And fixing it,
together with another issue (double address byte), needed all this
refactoring.

I might try to recap how this double data byte problem was triggered.
This is somewhere on my todo-list anyhow. Just to check if the same
problem is still present with Gen3 SoCs. No promises, but I'll see what
I can do.

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