linux-kernel - [PATCH 3.4 148/176] ASoC: sgtl5000: add delay before first I2C access

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Message-Id: <1428569224-23820-148-git-send-email-lizf@kernel.org>
Date:	Thu,  9 Apr 2015 16:46:36 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Eric Nelson <eric.nelson@...ndarydevices.com>,
	Mark Brown <broonie@...nel.org>, Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 148/176] ASoC: sgtl5000: add delay before first I2C access

From: Eric Nelson <eric.nelson@...ndarydevices.com>

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit 58cc9c9a175885bbf6bae3acf18233d0a8229a84 upstream.

To quote from section 1.3.1 of the data sheet:
	The SGTL5000 has an internal reset that is deasserted
	8 SYS_MCLK cycles after all power rails have been brought
	up. After this time, communication can start

	...
	1.0us represents 8 SYS_MCLK cycles at the minimum 8.0 MHz SYS_MCLK.

Signed-off-by: Eric Nelson <eric.nelson@...ndarydevices.com>
Reviewed-by: Fabio Estevam <fabio.estevam@...escale.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 sound/soc/codecs/sgtl5000.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
index c40b7ca..87cbf14 100644
--- a/sound/soc/codecs/sgtl5000.c
+++ b/sound/soc/codecs/sgtl5000.c
@@ -1238,6 +1238,9 @@ static int sgtl5000_enable_regulators(struct snd_soc_codec *codec)
 	/* wait for all power rails bring up */
 	udelay(10);
 
+	/* Need 8 clocks before I2C accesses */
+	udelay(1);
+
 	/* read chip information */
 	reg = snd_soc_read(codec, SGTL5000_CHIP_ID);
 	if (((reg & SGTL5000_PARTID_MASK) >> SGTL5000_PARTID_SHIFT) !=
-- 
1.9.1

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