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gpio: pca953x: hack to fix 24 bit gpio expanders

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24 bit expanders use REG_ADDR_AI in combination with register addressing. This
conflicts with regmap which takes this bit as part of the register number,
i.e. a second cache entry is defined for accessed with REG_ADDR_AI being
set although on the chip it is the same register as with REG_ADDR_AI being
cleared.

The problem was introduced by

	commit b32cecb46b ("gpio: pca953x: Extract the register address mangling to single function")

but only became visible by

	commit 8b9f9d4dc5 ("regmap: verify if register is writeable before writing operations")

because before, the regmap size was effectively ignored and
pca953x_writeable_register() did know to ignore REG_ADDR_AI. Still, there
were two separate cache entries created.

Since the use of REG_ADDR_AI seems to be static we can work around this
issue by simply increasing the size of the regmap to cover the "virtual"
registers with REG_ADDR_AI being set. This only means that half of the
regmap buffer will be unused.

Reported-by: H. Nikolaus Schaller <hns@goldelico.com>
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
H. Nikolaus Schaller 2019-06-04 14:35:58 +02:00 committed by Linus Walleij
parent f2c7c76c5d
commit 3b00691cc4
1 changed files with 2 additions and 1 deletions
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3
drivers/gpio/gpio-pca953x.c
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@ -308,7 +308,8 @@ static const struct regmap_config pca953x_i2c_regmap = {
.volatile_reg = pca953x_volatile_register,
.cache_type = REGCACHE_RBTREE,
.max_register = 0x7f,
/* REVISIT: should be 0x7f but some 24 bit chips use REG_ADDR_AI */
.max_register = 0xff,
};
static u8 pca953x_recalc_addr(struct pca953x_chip *chip, int reg, int off,