On Fri, Feb 22, 2019 at 10:25:19AM +0100, Ludovic Desroches wrote:

[Ludovic Desroches: see Changes section]

Based on the discussion we had on the i2c-linux list [1], I wrote a patch for
AT91 hardware and tried to fulfill the Linux I2C slave interface description
[2] as good as possible. This enables aforementioned hardware to act as an I2C
slave that can be accessed by a remote I2C master.

I have tested this patchset successfully on an ATSAMA5D27.

                                 ^  3.3V   ^  3.3V
    +-----------------------+    |         |         +-----------------------+
    | Slave: ATSAMA5D27     |   +-+       +-+        | Master: ATSAMA5D35    |
    | with i2c-slave-eeprom |   | | 100k  | | 100k   | with i2cset           |
    +-------------------+-+-+   +-+       +-+        +-+-+-------------------+
                        | |      |         |           | |
                        | +------+---------|---(SDA)---+ |
                        +------------------+---(SCL)-----+

    Schematic: Connection of slave and master with 100kOhm pullup resistors.

On the master the following BASH script has been used to stress the slave.

        root@emblinux:~# cat ./stress.sh

        #!/bin/bash

Not everybody has bash in their environments. See below, how easily to switch
to regular shell.

#!/bin/sh

        I=0
        while true
        do
                if i2cset -y -r 1 0x64 0 $I w | grep mismatch
                then
                        echo "$(date): Error in transmission ${I}"
                fi

                ((I++))

I=$(($I+1))

                if [ $I -eq 65536 ]
                then
                        I=0
                        echo "$(date): Sent 65536 transmissions"
                fi

This one can be optimized to

for I in $(seq 65536); do
...
done

        done

After running the script for some time I had the following output. To me this
looks promising :)

        root@emblinux:~# ./stress.sh
        Thu Nov  9 13:58:45 CTE 2017: Sent 65536 transmissions
        Thu Nov  9 14:35:20 CTE 2017: Sent 65536 transmissions
        Thu Nov  9 15:12:11 CTE 2017: Sent 65536 transmissions
        Thu Nov  9 15:49:04 CTE 2017: Sent 65536 transmissions
        Thu Nov  9 16:26:00 CTE 2017: Sent 65536 transmissions
        Thu Nov  9 17:03:07 UTC 2017: Sent 65536 transmissions
        Thu Nov  9 17:40:15 UTC 2017: Sent 65536 transmissions

        If you have some hardware with an at91-i2c interface included at hand, I really
        would appreciate if you can run the test script on your hardware and test this
        driver.
        Thu Nov  9 17:40:15 UTC 2017: Sent 65536 transmissions

        If you have some hardware with an at91-i2c interface included at hand, I really
        would appreciate if you can run the test script on your hardware and test this
        driver.

-- 
With Best Regards,
Andy Shevchenko



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