Hello Tom,
Tom Rini wrote:
This reverts commit 0e57968a215d1b9d271f3fa5bebeddeaea0c8075.
The short version of the original commit is that some i2c devices cannot be probed via read as they NAK the first cycle, so try and probe via a write that we abort before it writes to the device. This however is not allowed by the TRM for any of these parts. The section on I2C_CON (table 17-35 I2C_CON for am/dm37x for example) says you must not change the register while STT has been set. On these parts, the unpredictable behavior that the chip exhibits is not problematic. On OMAP4 however it results in the chip being in a bad state: Panda # i2c probe Valid chip addresses: 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F 50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F 60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77 78 79 7A 7B 7C 7D 7E 7F Panda # i2c md 50 0 timed out in wait_for_pin: I2C_STAT=0 I2C read: I/O error Error reading the chip.
We must revert the original behavior to bring probe back into line with the TRM.
Cc: Nick Thompson nick.thompson@ge.com Cc: Heiko Schocher hs@denx.de Signed-off-by: Tom Rini trini@ti.com
drivers/i2c/omap24xx_i2c.c | 42 +++++++++++++++++++++++++++++++----------- 1 file changed, 31 insertions(+), 11 deletions(-)
Acked-by: Heiko Schocher hs@denx.de
Thanks!
bye, Heiko