linux-kernel - Re: [PATCH 2/2] ASoC: wm9081: Use snd_soc_update

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Date:	Tue, 18 Oct 2011 09:43:12 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	linux-kernel@...r.kernel.org,
	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, alsa-devel@...a-project.org
Subject: Re: [PATCH 2/2] ASoC: wm9081: Use snd_soc_update_bits for read-modify-write

2011/10/18 Mark Brown <broonie@...nsource.wolfsonmicro.com>:
> On Mon, Oct 17, 2011 at 12:36:52PM +0800, Axel Lin wrote:
>> Use snd_soc_update_bits for read-modify-write register access instead of
>> open-coding it using snd_soc_read and snd_soc_write
>
> Something in here is breaking audio through the WM9081 on Speyside.  I
> can't immediately spot anything wrong but the behaviour is quite obvious
> in the system.
>
hi Mark,
Thanks for testing.
I think the suspect part is here:

                        /* VMID 2*4k; Soft VMID ramp enable */
-                       reg = snd_soc_read(codec, WM9081_VMID_CONTROL);
-                       reg |= WM9081_VMID_RAMP | 0x6;
-                       snd_soc_write(codec, WM9081_VMID_CONTROL, reg);
-
+                       snd_soc_update_bits(codec, WM9081_VMID_CONTROL,
+                                           WM9081_VMID_RAMP | 0x6,
+                                           WM9081_VMID_RAMP | 0x6);
                        mdelay(100);

                        /* Normal bias enable & soft start off */
-                       reg |= WM9081_BIAS_ENA;
-                       reg &= ~WM9081_VMID_RAMP;
-                       snd_soc_write(codec, WM9081_VMID_CONTROL, reg);
+                       snd_soc_update_bits(codec, WM9081_VMID_CONTROL,
+                                           WM9081_VMID_RAMP | WM9081_BIAS_ENA,
+                                           WM9081_BIAS_ENA);

Original code does not change VMID_SEL[1:0] bits in the second write for
Normal bias enable & soft start off.

Maybe I should not convert it to snd_soc_update_bits for this case.

Regards,
Axel
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