linux-kernel - Re: [PATCH] regulator: twl4030 VAUX3 supports 3.0V

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Message-Id: <200903061116.21544.david-b@pacbell.net>
Date:	Fri, 6 Mar 2009 11:16:20 -0800
From:	David Brownell <david-b@...bell.net>
To:	Adrian Hunter <adrian.hunter@...ia.com>
Cc:	lrg@...mlogic.co.uk, LKML <linux-kernel@...r.kernel.org>,
	"linux-omap Mailing List" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] regulator: twl4030 VAUX3 supports 3.0V

On Friday 06 March 2009, Adrian Hunter wrote:
> TWL4030 and TWL5030 support 3.0V on VAUX3.

I double checked several technical reference manuals, and they
say otherwise.   The 3.0V settings in VAUX3_DEDICATED are very
consistently labeled as "TI cannot support these values", for
all current versions of chips with a VAUX3 supply:

  TWL4030 ES3.1
  TWL5030 ES1.1
  TPS65930 ES1.0 (more or less a cost-reduced TWL5030)
  TPS65950 ES1.0 (more or less TWL5030)

So, NAK on this.

Do you really need 3.0V out of that regulator?  If so,
then I'd rather see a patch exposing that CONFIG_*
setting to enable all the unsupported/out-of-range
values, rather than just selectively hacking those
tables to permit some (but not all) of them to be used
out-of-range.

> Signed-off-by: Adrian Hunter <adrian.hunter@...ia.com>
> ---
> 
> According to TI:
> http://community.ti.com/forums/t/3777.aspx

That looks to me like some random TI developer reading the
manual and ignoring the label on those settings:  Yes if you
set that value it'll probably work.  But no, if you rely on
that it's working out-of-spec, and is clearly marked as such.

> 
> 
>  drivers/regulator/twl4030-regulator.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/regulator/twl4030-regulator.c b/drivers/regulator/twl4030-regulator.c
> index 8655443..1755026 100644
> --- a/drivers/regulator/twl4030-regulator.c
> +++ b/drivers/regulator/twl4030-regulator.c
> @@ -224,7 +224,7 @@ static const u16 VAUX2_VSEL_table[] = {
>  };
>  static const u16 VAUX3_VSEL_table[] = {
>  	1500, 1800, 2500, 2800,
> -	UNSUP(3000), UNSUP(3000), UNSUP(3000), UNSUP(3000),
> +	3000, 3000, 3000, 3000,
>  };
>  static const u16 VAUX4_VSEL_table[] = {
>  	700, 1000, 1200, UNSUP(1300),
> -- 
> 1.5.6.3
> 
> 

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