On 12/02/2019 0.57, Tony Lindgren wrote:
> 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.
Acked-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
>
> Cc: Florian Vaussard <florian.vaussard@xxxxxxx>
> Cc: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
> ---
> drivers/mfd/twl6040.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mfd/twl6040.c b/drivers/mfd/twl6040.c
> --- 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, "%s register write failed: %i\n",
> + __func__, ret);
> + goto out;
> + }
>
> /* Default PLL configuration after power up */
> twl6040->pll = TWL6040_SYSCLK_SEL_LPPLL;
>
- Péter
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