From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wj0-f195.google.com ([209.85.210.195]:34264 "EHLO mail-wj0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753640AbcK0LMm (ORCPT ); Sun, 27 Nov 2016 06:12:42 -0500 Received: by mail-wj0-f195.google.com with SMTP id xy5so10599365wjc.1 for ; Sun, 27 Nov 2016 03:12:41 -0800 (PST) Date: Sun, 27 Nov 2016 12:12:36 +0100 From: Marcel Hasler To: Ezequiel Garcia , Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Subject: [PATCH v3 4/4] stk1160: Give the chip some time to retrieve data from AC97 codec. Message-ID: <20161127111236.GA1691@arch-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161127110732.GA5338@arch-desktop> Sender: linux-media-owner@vger.kernel.org List-ID: 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 --- drivers/media/usb/stk1160/stk1160-ac97.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/media/usb/stk1160/stk1160-ac97.c b/drivers/media/usb/stk1160/stk1160-ac97.c index 60327af..b39f51b 100644 --- a/drivers/media/usb/stk1160/stk1160-ac97.c +++ b/drivers/media/usb/stk1160/stk1160-ac97.c @@ -23,6 +23,7 @@ * */ +#include #include #include "stk1160.h" @@ -64,6 +65,14 @@ 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 the data. + * The proper way would be to poll STK1160_AC97CTL_0 + * until the command bit has been cleared, but this + * may not be worth the hassle. + */ + usleep_range(20, 40); + /* Retrieve register value */ stk1160_read_reg(dev, STK1160_AC97_CMD, &vall); stk1160_read_reg(dev, STK1160_AC97_CMD + 1, &valh); -- 2.10.2