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Subject: [media] em28xx: fix Terratec Grabby AC97 codec detection Author: Matthieu Rogez <[email protected]> Date: Fri Mar 4 18:33:08 2016 -0300 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. We also check that unrelated registers don't return the same value. This second check handles the case where the expected value is constantly returned no matter which register is accessed. Signed-off-by: Matthieu Rogez <[email protected]> Signed-off-by: Mauro Carvalho Chehab <[email protected]> drivers/media/usb/em28xx/em28xx-cards.c | 38 +++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) --- http://git.linuxtv.org/cgit.cgi/media_tree.git/commit/?id=0899f62ff93f73860a23a4d4ac6921e3786b41d1 diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c index 5e127e48c945..930e3e3fc948 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 +2564,36 @@ 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 reliably before proceeding. + * We also check that two unrelated registers accesses don't return the same + * value to avoid premature return. + * This procedure helps ensuring AC97 register accesses are reliable. + */ +static int em28xx_wait_until_ac97_features_equals(struct em28xx *dev, + int expected_feat) +{ + unsigned long timeout = jiffies + msecs_to_jiffies(2000); + int feat, powerdown; + + while (time_is_after_jiffies(timeout)) { + feat = em28xx_read_ac97(dev, AC97_RESET); + if (feat < 0) + return feat; + + powerdown = em28xx_read_ac97(dev, AC97_POWERDOWN); + if (powerdown < 0) + return powerdown; + + if (feat == expected_feat && feat != powerdown) + return 0; + + msleep(50); + } + + em28xx_warn("AC97 registers access is not reliable !\n"); + return -ETIMEDOUT; +} + /* Since em28xx_pre_card_setup() requires a proper dev->model, * this won't work for boards with generic PCI IDs */ @@ -2668,6 +2699,13 @@ 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); _______________________________________________ linuxtv-commits mailing list [email protected] http://www.linuxtv.org/cgi-bin/mailman/listinfo/linuxtv-commits
