Re: [PATCH] i2c-davinci: Handle signals gracefully
From: Mike Looijmans
Date: Mon Mar 10 2014 - 06:25:09 EST
ïOn 03/09/2014 09:21 PM, Wolfram Sang wrote:
On Thu, Jan 09, 2014 at 12:11:25PM +0100, Mike Looijmans wrote:
When a signal is caught while the i2c-davinci bus driver is transferring,
the drive just "abandons" the transfer and leaves the controller to fend
for itself. The next I2C transaction will find the controller in an
undefined state and often results in a stream of "initiating i2c bus recovery"
messages until the controller arrives in a defined state. This behaviour
also sends out "half" or possibly even mixed messages to I2C client
devices which may put them in an undesired state as well.
This patch fixes this issue by always attempting to finish the current
transaction, and then check on a pending signal. It either reports
success if all data has been transferred, or it returns failure when
the transaction was aborted. This keeps the controller in a defined
state, and is also much friendlier towards client devices, because
it will only send complete messages.
Even more, you should complete the whole transfer. There are devices
where things can really go wrong if you send a half-complete command and
then start with the next one. So, not checking signals at all is the way
to go for I2C drivers. There is some cruft left, so I am happy about
patches fixing that, with testing on real HW. Like yours here.
I agree.
I know the Zynq (using a cadence controller) also lets signals interrupt I2C
transfers, so I'll propose a patch to Xilinx and CC to you and linux-i2c to
completely remove signal handling from that driver as well.
Mike
Met vriendelijke groet / kind regards,
Mike Looijmans
TOPIC Embedded Systems
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