From: Tony Lindgren tony@atomide.com
[ Upstream commit 48171d0ea7caccf21c9ee3ae75eb370f2a756062 ]
I noticed that we can get a -EREMOTEIO errors on at least omap4 duovero:
twl6040 0-004b: Failed to write 2d = 19: -121
And then any following register access will produce errors.
There 2d offset above is register ACCCTL that gets written on twl6040 powerup. With error checking added to the related regcache_sync() call, the -EREMOTEIO error is reproducable on twl6040 powerup at least duovero.
To fix the error, we need to wait until twl6040 is accessible after the powerup. Based on tests on omap4 duovero, we need to wait over 8ms after powerup before register write will complete without failures. Let's also make sure we warn about possible errors too.
Note that we have twl6040_patch[] reg_sequence with the ACCCTL register configuration and regcache_sync() will write the new value to ACCCTL.
Signed-off-by: Tony Lindgren tony@atomide.com Acked-by: Peter Ujfalusi peter.ujfalusi@ti.com Signed-off-by: Lee Jones lee.jones@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mfd/twl6040.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/mfd/twl6040.c b/drivers/mfd/twl6040.c index dd19f17a1b637..2b8c479dbfa6e 100644 --- a/drivers/mfd/twl6040.c +++ b/drivers/mfd/twl6040.c @@ -322,8 +322,19 @@ int twl6040_power(struct twl6040 *twl6040, int on) } }
+ /* + * Register access can produce errors after power-up unless we + * wait at least 8ms based on measurements on duovero. + */ + usleep_range(10000, 12000); + /* Sync with the HW */ - regcache_sync(twl6040->regmap); + ret = regcache_sync(twl6040->regmap); + if (ret) { + dev_err(twl6040->dev, "Failed to sync with the HW: %i\n", + ret); + goto out; + }
/* Default PLL configuration after power up */ twl6040->pll = TWL6040_SYSCLK_SEL_LPPLL;