Messages in this thread |  | | Subject | Re: [PATCH v3 2/7] i2c: bcm2835: Protect against unexpected TXW/RXR interrupts | From | Noralf Trønnes <> | Date | Sun, 2 Oct 2016 16:19:57 +0200 |
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Den 29.09.2016 07:37, skrev Stefan Wahren: >> Noralf Trønnes <noralf@tronnes.org> hat am 29. September 2016 um 00:22 >> geschrieben: >> >> >> >> Den 29.09.2016 00:00, skrev Eric Anholt: >>> Noralf Trønnes <noralf@tronnes.org> writes: >>> >>>> If an unexpected TXW or RXR interrupt occurs (msg_buf_remaining == 0), >>>> the driver has no way to fill/drain the FIFO to stop the interrupts. >>>> In this case the controller has to be disabled and the transfer >>>> completed to avoid hang. >>>> >>>> (CLKT | ERR) and DONE interrupts are completed in their own paths, and >>>> the controller is disabled in the transfer function after completion. >>>> Unite the code paths and do disabling inside the interrupt routine. >>>> >>>> Clear interrupt status bits in the united completion path instead of >>>> trying to do it on every interrupt which isn't necessary. >>>> Only CLKT, ERR and DONE can be cleared that way. >>>> >>>> Add the status value to the error value in case of TXW/RXR errors to >>>> distinguish them from the other S_LEN error. >>> I was surprised that not writing the TXW/RXR bits on handling their >>> interrupts was OK, given that we were doing so before, but it's a level >>> interrupt and those bits are basically ignored on write. >>> >>> This patch and 3, 4, and 6 are: >>> >>> Reviewed-by: Eric Anholt <eric@anholt.net> >>> >>> Patch 5 is: >>> >>> Acked-by: Eric Anholt <eric@anholt.net> >>> >>> Note for future debug: The I2C_C_CLEAR on errors will take some time to >>> resolve -- if you were in non-idle state and I2C_C_READ, it sets an >>> abort_rx flag and runs through the state machine to send a NACK and a >>> STOP, I think. Since we're setting CLEAR without I2CEN, that NACK will >>> be hanging around queued up for next time we start the engine. >> Maybe you're able to explain the issues I had with reset: >> https://github.com/raspberrypi/linux/issues/1653 >> >> Should we put your note into the commit message? >> It will most likely be lost if it just stays in this email. > I prefer to have this kind of information as a code comment.
Eric, does this look good to you as a code comment:
/* * Note about I2C_C_CLEAR on error: * The I2C_C_CLEAR on errors will take some time to resolve -- if you were in * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through * the state machine to send a NACK and a STOP. Since we're setting CLEAR * without I2CEN, that NACK will be hanging around queued up for next time * we start the engine. */
If it is, I'll resend the series with this change and add all the ack's and r-b's.
Noralf.
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