linux-kernel - [PATCH] sound/sgtl5000: fix codec clock source transition to avoid clockless moment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	5 Aug 2013 07:36:02 +0000
From:	"Oskar Schirmer" <oskar@...ra.com>
To:	"Fabio Estevam" <fabio.estevam@...escale.com>
Cc:	alsa-devel@...a-project.org, "Mark Brown" <broonie@...nel.org>,
	linux-kernel@...r.kernel.org,
	"Zeng Zhaoming" <zengzm.kernel@...il.com>,
	"Oskar Schirmer" <oskar@...ra.com>
Subject: [PATCH] sound/sgtl5000: fix codec clock source transition to avoid clockless moment

Powering down PLL before switching to a mode that does not use it
is a bad idea. It would cause the SGTL5000 be without internal
clock supply, especially on the I2C interface, which would make
subsequent access to it fail.

Thus, in case of not using PLL any longer, first set the mode
control, then power down PLL.

Signed-off-by: Oskar Schirmer <oskar@...ra.com>
---
 sound/soc/codecs/sgtl5000.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
index 6c8a9e7..8ecb201 100644
--- a/sound/soc/codecs/sgtl5000.c
+++ b/sound/soc/codecs/sgtl5000.c
@@ -644,16 +644,19 @@ static int sgtl5000_set_clock(struct snd_soc_codec *codec, int frame_rate)
 		snd_soc_update_bits(codec, SGTL5000_CHIP_ANA_POWER,
 			SGTL5000_PLL_POWERUP | SGTL5000_VCOAMP_POWERUP,
 			SGTL5000_PLL_POWERUP | SGTL5000_VCOAMP_POWERUP);
+
+		/* if using pll, clk_ctrl must be set after pll power up */
+		snd_soc_write(codec, SGTL5000_CHIP_CLK_CTRL, clk_ctl);
 	} else {
+		/* otherwise, clk_ctrl must be set before pll power down */
+		snd_soc_write(codec, SGTL5000_CHIP_CLK_CTRL, clk_ctl);
+
 		/* power down pll */
 		snd_soc_update_bits(codec, SGTL5000_CHIP_ANA_POWER,
 			SGTL5000_PLL_POWERUP | SGTL5000_VCOAMP_POWERUP,
 			0);
 	}
 
-	/* if using pll, clk_ctrl must be set after pll power up */
-	snd_soc_write(codec, SGTL5000_CHIP_CLK_CTRL, clk_ctl);
-
 	return 0;
 }
 
-- 
1.7.9.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/