| Message ID | 9bb9ca6102e795dc2495d92b7b661779509adebc.1559651758.git.hns@goldelico.com |
|---|---|
| State | New |
| Headers | show |
| Series | gpio: pca953x: hack to fix 24 bit gpio expanders | expand |
On Tue, Jun 4, 2019 at 2:36 PM H. Nikolaus Schaller <hns@goldelico.com> wrote: > 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 b32cecb46bdc ("gpio: pca953x: Extract the register address mangling to single function") > > but only became visible by > > commit 8b9f9d4dc511 ("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> Patch queued for fixes, let's think about better solutions going forward. Yours, Linus Walleij
diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c index b7ef33f63392..2b27d18410aa 100644 --- a/drivers/gpio/gpio-pca953x.c +++ b/drivers/gpio/gpio-pca953x.c @@ -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,
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 b32cecb46bdc ("gpio: pca953x: Extract the register address mangling to single function") but only became visible by commit 8b9f9d4dc511 ("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> --- drivers/gpio/gpio-pca953x.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)