Subject: [PATCH 1/2] mfd: twl6040: Fix deferred probe handling for clk32k

From: [email-masked] (Peter Ujfalusi)
Date: Mon, 21 Sep 2015 12:55:46 +0300

On 09/18/2015 07:29 PM, Tony Lindgren wrote:
> Commit 68bab8662f49 ("mfd: twl6040: Optional clk32k clock handling")
> added clock handling for the 32k clock from palmas-clk. However, that
> patch did not consider a typical situation where twl6040 is built-in,
> and palmas-clk is a loadable module like we have in omap2plus_defconfig.
> 
> If palmas-clk is not loaded before twl6040 probes, we will get a
> "clk32k is not handled" warning during booting. This means that any
> drivers relying on this clock will mysteriously fail, including
> omap5-uevm WLAN and audio.
> 
> Note that for WLAN, we probably should also eventually get
> the clk32kgaudio for MMC3 directly as that's shared between
> audio and WLAN SDIO at least for omap5-uevm. It seems the
> WLAN chip cannot get it as otherwise MMC3 won't get properly
> probed.

While this is going to 'fix' the WLAN because currently the twl6040 is powered
on all the time (32k clock is enabled). My plan is to finally implement the
power state handling for the twl6040, which means that w/o audio activity the
twl6040 will be turned off. This will imply that any clock which is only used
by twl6040 will be off as well.
The proper solution would be to add clock handling to the WLAN driver stack.

Otherwise:
Acked-by: Peter Ujfalusi <[email-masked]>

> Fixes: 68bab8662f49 ("mfd: twl6040: Optional clk32k clock handling")
> Cc: Benoit Cousson <[email-masked]>
> Cc: Dr. H. Nikolaus Schaller <[email-masked]>
> Cc: Grazvydas Ignotas <[email-masked]>
> Cc: Lee Jones <[email-masked]>
> Cc: Peter Ujfalusi <[email-masked]>
> Cc: Samuel Ortiz <[email-masked]>
> Cc: Sourav Poddar <[email-masked]>
> Signed-off-by: Tony Lindgren <[email-masked]>
> ---
>  drivers/mfd/twl6040.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> --- a/drivers/mfd/twl6040.c
> +++ b/drivers/mfd/twl6040.c
> @@ -647,6 +647,8 @@ static int twl6040_probe(struct i2c_client *client,
>  
>  	twl6040->clk32k = devm_clk_get(&client->dev, "clk32k");
>  	if (IS_ERR(twl6040->clk32k)) {
> +		if (PTR_ERR(twl6040->clk32k) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
>  		dev_info(&client->dev, "clk32k is not handled\n");
>  		twl6040->clk32k = NULL;
>  	}
> 

-- 
P?ter