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authorWolfram Sang <wsa+renesas@sang-engineering.com>2018-06-29 11:12:46 +0200
committerWolfram Sang <wsa@the-dreams.de>2018-07-03 23:09:01 +0200
commit16d55daa56cd7520055758f98f96e8544cc7713e (patch)
treec1d02faad2e07303e07f32b5d97f0e45256a5428 /Documentation/i2c
parentd07bdbc02cdf9930da5f4b8b502c8b33a6d29fcf (diff)
downloadlinux-16d55daa56cd7520055758f98f96e8544cc7713e.tar.bz2
i2c: gpio: fault-injector: refactor incomplete transfer
Make the incomplete_transfer routine reusable, so we can add other test cases with different patterns later. Prepare the docs for that, too. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'Documentation/i2c')
-rw-r--r--Documentation/i2c/gpio-fault-injection30
1 files changed, 19 insertions, 11 deletions
diff --git a/Documentation/i2c/gpio-fault-injection b/Documentation/i2c/gpio-fault-injection
index e0c4f775e239..37542461cea4 100644
--- a/Documentation/i2c/gpio-fault-injection
+++ b/Documentation/i2c/gpio-fault-injection
@@ -34,21 +34,29 @@ I2C specification version 4, section 3.1.16) using the helpers of the Linux I2C
core (see 'struct bus_recovery_info'). However, the bus recovery will not
succeed because SDA is still pinned low until you manually release it again
with "echo 1 > sda". A test with an automatic release can be done with the
-'incomplete_transfer' file.
+following class of fault injectors.
-"incomplete_transfer"
----------------------
+Introduction to incomplete transfers
+------------------------------------
+
+The following fault injectors create situations where SDA will be held low by a
+device. Bus recovery should be able to fix these situations. But please note:
+there are I2C client devices which detect a stuck SDA on their side and release
+it on their own after a few milliseconds. Also, there might be an external
+device deglitching and monitoring the I2C bus. It could also detect a stuck SDA
+and will init a bus recovery on its own. If you want to implement bus recovery
+in a bus master driver, make sure you checked your hardware setup for such
+devices before. And always verify with a scope or logic analyzer!
+
+"incomplete_address_phase"
+--------------------------
This file is write only and you need to write the address of an existing I2C
-client device to it. Then, a transfer to this device will be started, but it
-will stop at the ACK phase after the address of the client has been
+client device to it. Then, a read transfer to this device will be started, but
+it will stop at the ACK phase after the address of the client has been
transmitted. Because the device will ACK its presence, this results in SDA
being pulled low by the device while SCL is high. So, similar to the "sda" file
above, the bus master under test should detect this condition and try a bus
recovery. This time, however, it should succeed and the device should release
-SDA after toggling SCL. Please note: there are I2C client devices which detect
-a stuck SDA on their side and release it on their own after a few milliseconds.
-Also, there are external devices deglitching and monitoring the I2C bus. They
-can also detect a stuck SDA and will init a bus recovery on their own. If you
-want to implement bus recovery in a bus master driver, make sure you checked
-your hardware setup carefully before.
+SDA after toggling SCL.
+