2016-11-20 18:37 GMT+01:00 Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>: > On 28 October 2016 at 05:52, Marcel Hasler <mahasler@xxxxxxxxx> wrote: >> The STK1160 needs some time to transfer data from the AC97 registers into its own. On some >> systems reading the chip's own registers to soon will return wrong values. The "proper" way to >> handle this would be to poll STK1160_AC97CTL_0 after every read or write command until the >> command bit has been cleared, but this may not be worth the hassle. >> >> Signed-off-by: Marcel Hasler <mahasler@xxxxxxxxx> >> --- >> drivers/media/usb/stk1160/stk1160-ac97.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/media/usb/stk1160/stk1160-ac97.c b/drivers/media/usb/stk1160/stk1160-ac97.c >> index 31bdd60d..caa65a8 100644 >> --- a/drivers/media/usb/stk1160/stk1160-ac97.c >> +++ b/drivers/media/usb/stk1160/stk1160-ac97.c >> @@ -20,6 +20,7 @@ >> * >> */ >> >> +#include <linux/delay.h> >> #include <linux/module.h> >> >> #include "stk1160.h" >> @@ -61,6 +62,9 @@ static u16 stk1160_read_ac97(struct stk1160 *dev, u16 reg) >> */ >> stk1160_write_reg(dev, STK1160_AC97CTL_0, 0x8b); >> >> + /* Give the chip some time to transfer data */ >> + usleep_range(20, 40); >> + > > I don't recall any issues with this. In any case, we only read the registers > for debugging purposes, so it's not a big deal. > I actually just re-tested this, as I recently replaced my computer's main board. I didn't happen with my old one, but it does with my new one, just as with both of my notebooks. > Maybe it would be better to expand the comment a little bit, > using your commit log: > > "" > The "proper" way to > handle this would be to poll STK1160_AC97CTL_0 after > every read or write command until the command bit > has been cleared, but this may not be worth the hassle. > "" > > This way, if the sleep proves problematic in the future, > the "proper way" is already documented. > >> /* Retrieve register value */ >> stk1160_read_reg(dev, STK1160_AC97_CMD, &vall); >> stk1160_read_reg(dev, STK1160_AC97_CMD + 1, &valh); >> -- >> 2.10.1 >> > > > > -- > Ezequiel García, VanguardiaSur > www.vanguardiasur.com.ar -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
