From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: linux-i2c@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Phil Reid <preid@electromag.com.au>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Jarkko Nikula <jarkko.nikula@linux.intel.com>,
Claudio Foellmi <claudio.foellmi@ergon.ch>,
Andrzej Hajda <a.hajda@samsung.com>
Subject: [PATCH 0/6] i2c: send STOP after recovery; use it for i2c-rcar
Date: Mon, 4 Dec 2017 13:36:34 +0100 [thread overview]
Message-ID: <20171204123640.3382-1-wsa+renesas@sang-engineering.com> (raw)
When implementing bus recovery for the i2c-rcar driver, two problems were
encountered: 1) When reading the SDA bit, not the SDA status was returned but
the internal state of the "bus_is_busy" logic. 2) This logic needs a STOP to
consider the bus free again. SCL/SDA high is not enough, and there is no other
way known to reset the internal logic otherwise.
The obvious solution to just send STOP after recovery makes sense for the
generic case, too, IMO. If we made a device release SDA again, and are about
start a new transfer using START, then we should terminate the previous state
properly with STOP. This may help with some devices and shouldn't create any
drawback AFAICS.
For this, we need to introduce a 'set_sda' callback to the recovery
infrastructure. Because of this and some other minor recovery core changes, I
CCed a few people working on I2C bus recovery recently. The first five patches
may be interesting for you, so your input is greatly appreciated. Also, testing
the new features with GPIO based recovery would be awesome to have.
This was tested on a Renesas Lager board (r8a7790/R-Car H2). My test procedure
is documented here:
https://elinux.org/Tests:I2C-bus-recovery
A branch is available here:
git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/rcar-i2c-recovery
Please let me know what you think.
Kind regards,
Wolfram
Wolfram Sang (6):
i2c: make kerneldoc about bus recovery more precise
i2c: add identifier in declarations for i2c_bus_recovery
i2c: add 'set_sda' to bus_recovery_info
i2c: ensure SDA is released in recovery if SDA is controllable
i2c: send STOP after successful bus recovery
i2c: rcar: implement bus recovery
drivers/i2c/busses/i2c-rcar.c | 54 +++++++++++++++++++++++++++++++++++++++++--
drivers/i2c/i2c-core-base.c | 25 +++++++++++++++++++-
include/linux/i2c.h | 20 +++++++++-------
3 files changed, 88 insertions(+), 11 deletions(-)
--
2.11.0
next reply other threads:[~2017-12-04 12:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20171204123700epcas2p4273f3313a4c52e7685bbf04d776cbcef@epcas2p4.samsung.com>
2017-12-04 12:36 ` Wolfram Sang [this message]
2017-12-04 12:36 ` [PATCH 1/6] i2c: make kerneldoc about bus recovery more precise Wolfram Sang
2017-12-04 12:36 ` [PATCH 2/6] i2c: add identifier in declarations for i2c_bus_recovery Wolfram Sang
2017-12-13 15:23 ` Andy Shevchenko
2018-01-09 11:17 ` Wolfram Sang
2017-12-04 12:36 ` [PATCH 3/6] i2c: add 'set_sda' to bus_recovery_info Wolfram Sang
2017-12-05 1:12 ` Phil Reid
2017-12-05 8:39 ` Linus Walleij
2017-12-05 9:57 ` Phil Reid
2017-12-05 10:32 ` Wolfram Sang
2017-12-05 10:34 ` Linus Walleij
2017-12-05 13:38 ` Wolfram Sang
2017-12-05 15:31 ` Linus Walleij
2017-12-05 16:43 ` Wolfram Sang
2017-12-07 11:25 ` Wolfram Sang
2017-12-10 0:24 ` Linus Walleij
2017-12-13 15:30 ` Andy Shevchenko
2018-01-09 11:23 ` Wolfram Sang
2017-12-13 15:27 ` Andy Shevchenko
2017-12-04 12:36 ` [PATCH 4/6] i2c: ensure SDA is released in recovery if SDA is controllable Wolfram Sang
2017-12-04 12:36 ` [PATCH 5/6] i2c: send STOP after successful bus recovery Wolfram Sang
2017-12-04 12:36 ` [PATCH 6/6] i2c: rcar: implement " Wolfram Sang
2017-12-05 1:13 ` [PATCH 0/6] i2c: send STOP after recovery; use it for i2c-rcar Phil Reid
2017-12-05 9:21 ` Andrzej Hajda
2018-01-09 11:15 ` Wolfram Sang
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