Em Sun, 28 Feb 2016 12:26:23 +0100
Matthieu Rogez <matthieu.rogez@xxxxxxxxx> escreveu:
> EMP202 chip inside Terratec Grabby (hw rev 2) seems to require some time before
> accessing reliably its registers. Otherwise it returns some values previously
> put on the I2C bus.
>
> To account for that period, we delay card setup until we have a proof that
> accessing AC97 registers is reliable. We get this proof by polling AC97_RESET
> until the expected value is read.
>
> Signed-off-by: Matthieu Rogez <matthieu.rogez@xxxxxxxxx>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index 5e127e4..2e04902 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -37,6 +37,7 @@
> #include <media/i2c-addr.h>
> #include <media/tveeprom.h>
> #include <media/v4l2-common.h>
> +#include <sound/ac97_codec.h>
>
> #include "em28xx.h"
>
> @@ -2563,6 +2564,24 @@ static inline void em28xx_set_model(struct em28xx *dev)
> dev->def_i2c_bus = dev->board.def_i2c_bus;
> }
>
> +/* Wait until AC97_RESET reports the expected value (or reading error)
> + * before proceeding.
> + * This can help ensuring AC97 register accesses are reliable.
> + */
> +static int em28xx_wait_until_ac97_features_equals(struct em28xx *dev,
> + int expected_feat)
> +{
> + int feat;
> +
> + do {
> + feat = em28xx_read_ac97(dev, AC97_RESET);
> + if (feat < 0)
> + return feat;
> + } while (feat != expected_feat);
Please add some sort of timeout here... We don't want the Kernel to
be in a dead lock here...
> +
> + return 0;
> +}
> +
> /* Since em28xx_pre_card_setup() requires a proper dev->model,
> * this won't work for boards with generic PCI IDs
> */
> @@ -2668,6 +2687,13 @@ static void em28xx_pre_card_setup(struct em28xx *dev)
> em28xx_write_reg(dev, EM2820_R08_GPIO_CTRL, 0xfd);
> msleep(70);
> break;
> +
> + case EM2860_BOARD_TERRATEC_GRABBY:
> + /* HACK?: Ensure AC97 register reading is reliable before
> + * proceeding. In practice, this will wait about 1.6 seconds.
> + */
> + em28xx_wait_until_ac97_features_equals(dev, 0x6a90);
> + break;
> }
>
> em28xx_gpio_set(dev, dev->board.tuner_gpio);
--
Thanks,
Mauro
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