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| H A D | omap24xx_i2c.c | 168a5acb81a8d92a7effcb2727aaa89367b97e05 Mon May 21 06:46:29 UTC 2012 Tom Rini <trini@ti.com> Revert "I2C: OMAP: detect more devices when probing an i2c bus"
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>
Acked-by: Heiko Schocher <hs@denx.de>
0e57968a215d1b9d271f3fa5bebeddeaea0c8075 Mon Apr 11 22:37:41 UTC 2011 Nick Thompson <nick.thompson@ge.com> I2C: OMAP: detect more devices when probing an i2c bus
The omap24xx driver only seems to support devices that have a single subaddress
byte. With these types of devices, the first access in a bus transaction is
usually a write (writes the subaddress) followed by either a read or write to
access the devices registers.
Many such devices will respond to a read as the first access, but there are at
least some that will NACK such a read. (e.g. ADV7180.)
The probe function attempts to detect a devices ACK to a read access only and
fails to find devices that NACK a read.
This commit modifies the probe function to start a write instead. This detects
devices that respond to reads (since they must also respond to writes) as well
as those that only respond to writes. The bus is immediately set to idle after a
(N)ACK avoiding actually writing anything to the device.
Signed-off-by: Nick Thompson <nick.thompson@ge.com>
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