Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932288AbcCCR03 (ORCPT ); Thu, 3 Mar 2016 12:26:29 -0500 Received: from lists.s-osg.org ([54.187.51.154]:34121 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752052AbcCCR02 (ORCPT ); Thu, 3 Mar 2016 12:26:28 -0500 Date: Thu, 3 Mar 2016 14:26:21 -0300 From: Mauro Carvalho Chehab To: Matthieu Rogez Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] [media] em28xx: fix Terratec Grabby AC97 codec detection Message-ID: <20160303142621.62325571@recife.lan> In-Reply-To: <1456658783-32345-4-git-send-email-matthieu.rogez@gmail.com> References: <1456658783-32345-1-git-send-email-matthieu.rogez@gmail.com> <1456658783-32345-4-git-send-email-matthieu.rogez@gmail.com> Organization: Samsung X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.29; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2366 Lines: 76 Em Sun, 28 Feb 2016 12:26:23 +0100 Matthieu Rogez 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 > --- > 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 > #include > #include > +#include > > #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