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mfd: stmpe: Fix RESET regression on STMPE2401

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Since commit c4dd1ba355
("mfd: stmpe: Add reset support for all STMPE variant")
we're resetting the STMPE expanders before use.

This caused a regression on the STMP2401 on the Nomadik
NHK8815:

stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101
nmk-i2c 101f8000.i2c0: write to slave 0x43 timed out
nmk-i2c 101f8000.i2c0: no ack received after address transmission
stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101
nmk-i2c 101f8000.i2c0: write to slave 0x44 timed out
nmk-i2c 101f8000.i2c0: no ack received after address transmission

It turns out that we start to poll for the reset bit to
go low again too quickly: the STMPE2401 is not yet online and
ready to be asked for the status of the RESET bit.

By introducing a 10ms delay before starting to hammer
the register for information, we get back to normal:

stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101
stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101

Cc: [email protected]
Cc: Amelie Delaunay <[email protected]>
Fixes: c4dd1ba355 ("mfd: stmpe: Add reset support for all STMPE variant")
Signed-off-by: Linus Walleij <[email protected]>
Acked-by: Patrice Chotard <[email protected]>
Signed-off-by: Lee Jones <[email protected]>
This commit is contained in:
Linus Walleij 2016-11-01 10:22:53 +01:00 • committed by Lee Jones
commit f40584200b
1 changed files with 2 additions and 0 deletions
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2
drivers/mfd/stmpe.c
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@ -851,6 +851,8 @@ static int stmpe_reset(struct stmpe *stmpe)
if (ret < 0)
return ret;
msleep(10);
timeout = jiffies + msecs_to_jiffies(100);
while (time_before(jiffies, timeout)) {
ret = __stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_SYS_CTRL]);