Some of the chips supported by the pca953x driver need the most
significant bit in the address word set to automatically increment the
address pointer on subsequent reads and writes (example: PCA9505). With
this bit unset the same register is read multiple times on a multi-byte
read sequence. Other chips must not have this bit set and autoincrement
always (example: PCA9555).

Up to now this AI bit was interpreted to be part of the address, which
resulted in inconsistent regmap caching when a register was written with
AI set and then read without it. This happened for the PCA9505 in
pca953x_gpio_set_multiple() where pca953x_read_regs() bulk read from the
cache for registers 0x8-0xc and then wrote to registers 0x88-0x8c. (Side
note: reading 5 values from offset 0x8 yiels OP0 5 times because AI must
be set to get OP0-OP4, which is another bug that is resolved here as a
by-product.) The same problem happens when calls to gpio_set_value() and
gpio_set_array_value() were mixed.

With this patch the AI bit is always set for chips that support it. This
works as there are no code locations that make use of the behaviour with
AI unset (for the chips that support it).

Note that the call to pca953x_setup_gpio() had to be done a bit earlier
to make the NBANK macro work.

The history of this bug is a bit complicated. Commit b32cecb4
("gpio: pca953x: Extract the register address mangling to single
function") changed which chips and functions are affected. Commit
3b00691c ("gpio: pca953x: hack to fix 24 bit gpio expanders") used
some duct tape to make the driver at least appear to work. Commit
49427232 ("gpio: pca953x: Perform basic regmap conversion")
introduced the caching. Commit b4818afe ("gpio: pca953x: Add
set_multiple to allow multiple bits to be set in one write.") introduced
the .set_multiple() callback which didn't work for chips that need the
AI bit which was fixed later for some chips in 8958262a ("gpio:
pca953x: Repair multi-byte IO address increment on PCA9575"). So I'm
sorry, I don't know which commit I should pick for a Fixes: line.
Tested-by: Marcel Gudert <m.gudert@eckelmann.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>