Patch "mfd: stmpe: Fix RESET regression on STMPE2401" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

mfd: stmpe: Fix RESET regression on STMPE2401

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mfd-stmpe-fix-reset-regression-on-stmpe2401.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Linus Walleij <[email protected]>
Date: Tue, 1 Nov 2016 10:22:53 +0100
Subject: mfd: stmpe: Fix RESET regression on STMPE2401

From: Linus Walleij <[email protected]>

commit f40584200bc4af7aa4399635b9ac213c62a13ae7 upstream.

Since commit c4dd1ba355aae2bc3d1213da6c66c53e3c31e028 ("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

---
 drivers/mfd/stmpe.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -761,6 +761,8 @@ static int stmpe1801_reset(struct stmpe
 	if (ret < 0)
 		return ret;
 
+	msleep(10);
+
 	timeout = jiffies + msecs_to_jiffies(100);
 	while (time_before(jiffies, timeout)) {
 		ret = __stmpe_reg_read(stmpe, STMPE1801_REG_SYS_CTRL);

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/gpio-do-not-double-check-direction-on-sleeping-chips.patch queue-4.8/mfd-stmpe-fix-reset-regression-on-stmpe2401.patch queue-4.8/i2c-mux-fix-up-dependencies.patch