Hi Sven, On Thu, Nov 30, 2017 at 02:03:23PM -0500, Sven Van Asbroeck wrote: > Summary > ------- > Some at24 eeproms have multiple i2c slave addresses. A patch introduced > between 4.14-rc5 and 4.14-rc6 breaks support for these eeproms: > reads/writes which start outside the first slave no longer work. > > 98e8201039afad5d2af87df9ac682f62f69c0c2f > (eeprom: at24: enable runtime pm support) > > How to reproduce > ---------------- > - I'm using the latest mainline at24 driver (4.15-rc1) > - I have a 24AA16/24LC16B on board, which is a 2048-byte eeprom, > made up of 8x 256-byte internal eeproms, all with their own i2c slave > address. Base i2c address is 0x50, so this results in the following > slave addresses: 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57 of > 256 bytes each. Thank you for reporting this. > > $ ls -l /sys/bus/i2c/devices/1-0050/eeprom > -rw------- 1 root root 2048 Nov 30 13:16 /sys/bus/i2c/devices/1-0050/eeprom > > Reading from the beginning to the end in one go works just fine: > $ hexdump -C /sys/bus/i2c/devices/1-0050/eeprom > 00000000 f8 6e cf 01 ff 01 00 00 03 00 58 41 18 00 00 00 |.n........XA....| > 00000010 53 61 74 20 4d 61 72 20 31 32 20 31 32 3a 35 35 |Sat Mar 12 12:55| > 00000020 3a 31 32 20 32 30 31 36 01 00 58 41 0f 00 00 00 |:12 2016..XA....| > 00000030 41 58 4d 2d 55 50 33 32 39 32 2d 30 38 32 34 00 |AXM-UP3292-0824.| > 00000040 02 00 58 41 0d 00 00 00 41 58 53 2d 55 50 33 4b |..XA....AXS-UP3K| > 00000050 2d 30 32 30 34 00 00 00 04 00 58 41 09 00 00 00 |-0204.....XA....| > 00000060 55 4e 54 31 34 30 30 42 34 00 00 00 0a 00 58 41 |UNT1400B4.....XA| > 00000070 01 00 00 00 32 00 00 00 09 00 58 41 01 00 00 00 |....2.....XA....| > 00000080 31 00 00 00 01 00 00 00 32 00 00 00 01 00 00 00 |1.......2.......| > 00000090 32 00 00 00 ff ff ff ff ff ff ff ff ff ff ff ff |2...............| > 000000a0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| > * > 00000800 > > Reading from somewhere in the middle (outside of first slave) gives > EACCESS: > $ dd if=/sys/bus/i2c/devices/1-0050/eeprom bs=1 skip=520 count=20 > dd: /sys/bus/i2c/devices/1-0050/eeprom: Permission denied > > Reading from somewhere in the middle (INSIDE of first slave) still works: > $ dd if=/sys/bus/i2c/devices/1-0050/eeprom bs=1 skip=20 count=20 | hexdump -C > 00000000 4d 61 72 20 31 32 20 31 32 3a 35 35 3a 31 32 20 |Mar 12 12:55:12 | > 00000010 32 30 31 36 |2016| > 00000014 > > Additional questions for the patch authors > ------------------------------------------ > 1. why is there a need to add pm_runtime support to a series of chips > (at24) which do not have any power management registers, hardware or > support ? Power management is not a property of the chip itself, it's external to it. The motivation for the patch was that the chip is powered together with other chips in a camera module. If it is not powered off, all other devices in the module will remain powered. This is undesirable. > > 2. why is the at24's pm_runtime support operating on its parent i2c bus? > Why can't the parent i2c bus driver be in charge of its own runtime pm? This is device specific, the I²C bus driver doesn't know about it. I have a patch that should address the problem, let me know if it works for you. -- Kind regards, Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx
