From: Wolfram Sang <wsa@the-dreams.de>
To: linux-i2c@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org,
Phil Reid <preid@electromag.com.au>,
Wolfram Sang <wsa+renesas@sang-engineering.com>
Subject: [PATCH v2 0/6] i2c: send STOP after recovery; use it for i2c-rcar
Date: Tue, 9 Jan 2018 14:58:53 +0100 [thread overview]
Message-ID: <20180109135859.20771-1-wsa@the-dreams.de> (raw)
From: Wolfram Sang <wsa+renesas@sang-engineering.com>
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. The first five patches may be interesting for anyone, so input
is greatly appreciated. Also, testing the new features with GPIO based recovery
would be awesome to have. Thanks to Phil for testing already!
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.
Changes since V1:
* add more identifiers in patch 2
* don't use GPIOF_* flags but hardocded '0'
* added Phil's Tested-by
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 | 26 ++++++++++++---------
3 files changed, 91 insertions(+), 14 deletions(-)
--
2.11.0
next reply other threads:[~2018-01-09 13:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-09 13:58 Wolfram Sang [this message]
2018-01-09 13:58 ` [PATCH v2 1/6] i2c: make kerneldoc about bus recovery more precise Wolfram Sang
2018-01-09 13:58 ` [PATCH v2 2/6] i2c: add identifier in declarations for i2c_bus_recovery Wolfram Sang
2018-01-09 13:58 ` [PATCH v2 3/6] i2c: add 'set_sda' to bus_recovery_info Wolfram Sang
2018-01-10 13:43 ` Linus Walleij
2018-01-09 13:58 ` [PATCH v2 4/6] i2c: ensure SDA is released in recovery if SDA is controllable Wolfram Sang
2018-01-09 13:58 ` [PATCH v2 5/6] i2c: send STOP after successful bus recovery Wolfram Sang
2018-01-09 13:58 ` [PATCH v2 6/6] i2c: rcar: implement " Wolfram Sang
2018-01-15 23:08 ` [PATCH v2 0/6] i2c: send STOP after recovery; use it for i2c-rcar Wolfram Sang
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