linux-kernel - Question about patch "i2c: omap: resize fifos before each message"

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Message-Id: <A20987D6-DEEC-488D-9655-36A4D186599B@gmail.com>
Date:	Wed, 3 Dec 2014 18:11:18 +0300
From:	Alexander Kochetkov <al.kochet@...il.com>
To:	Felipe Balbi <balbi@...com>
Cc:	Kevin Hilman <khilman@...nel.org>,
	Tony Lindgren <tony@...mide.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	linux-omap <linux-omap@...r.kernel.org>,
	linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Question about patch "i2c: omap: resize fifos before each message"

Felipe,

Question about the patch[1].

I want to change the code in a way to not touch fifo thresholds for each message.
Because:
1. dev->threshold is valid only with checking of transfer direction.
   So, if last transfer was transmission and ISR get RRDY interrupt from slave receiver,
   then dev->threshold is invalid. We must read threshold value from BUF register, to
   process correctly.
2. I want to avoid changing fifos before message submission, because IP can start receiving
   message in a slave mode (race).
3. dev->threshold is changed in range 1-fifo_size/2. So instead of RDR we get RRDY and
   for messages larger then fifo_size/2 we still get RRDY and RDR.

Felipe, do you have in mind why do you want to avoid RDR and XDR events?
Something about errata?

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/i2c/busses/i2c-omap.c?id=dd74548ddece4b9d68e5528287a272fa552c81d0

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