[PATCH] pxa: Remove unused MFP LPM definition

[David Hunter]

On 4/26/2010 8:16 PM, Eric Miao wrote:
> Instead of removing this potentially useful low power mode pin status, what
> about the following patch:

I think the name itself is confusing. All of the other MFP_LPM_ 
definitions state what the pin is going to do: drive high/low, pull 
high/low, or float. My (strictly document-derived) understanding of 
PXA27x is that you can only choose to drive or float a pin, while with 
PXA3xx you can do all of the above. What would MFP_LPM_INPUT do that 
MFP_LPM_FLOAT wouldn't?

> commit f5d406d50f924c82ddf469f120fa420f0499d901
> Author: Eric Miao<eric.y.miao at gmail.com>
> Date:   Tue Apr 27 11:14:24 2010 +0800
>
>      [ARM] pxa: allow MFP_LPM_INPUT to be explicitly specified
>
>      Signed-off-by: Eric Miao<eric.y.miao at gmail.com>
>
> diff --git a/arch/arm/mach-pxa/mfp-pxa2xx.c b/arch/arm/mach-pxa/mfp-pxa2xx.c
> index e5b7921..1d1419b 100644
> --- a/arch/arm/mach-pxa/mfp-pxa2xx.c
> +++ b/arch/arm/mach-pxa/mfp-pxa2xx.c
> @@ -81,6 +81,7 @@ static int __mfp_config_gpio(unsigned gpio, unsigned long c)
>   		PGSR(bank)&= ~mask;
>   		is_out = 1;
>   		break;
> +	case MFP_LPM_INPUT:
>   	case MFP_LPM_DEFAULT:
>   		break;

If I read this correctly, _DEFAULT will, on entry to LPM, change the pin 
direction to the one implied by bit 23 (MFP_DIR_IN/MFP_DIR_OUT). For 
_INPUT to live up to its name, maybe it should always float the pin, 
like this:

+	case MFP_LPM_INPUT:
+		is_out = 0;
+		break;
	case MFP_LPM_DEFAULT:
		break;

Also, I'm not sure what effect GAFR will have (if any) in LPM. Does the 
AF have to be set to GPIO to enable the PGSR/GPDR settings? Your 
original patch did just that:

[http://www.spinics.net/lists/arm-kernel/msg55842.html]

> diff --git a/arch/arm/plat-pxa/mfp.c b/arch/arm/plat-pxa/mfp.c
> index be58f9f..b77e018 100644
> --- a/arch/arm/plat-pxa/mfp.c
> +++ b/arch/arm/plat-pxa/mfp.c
> @@ -110,6 +110,7 @@ static const unsigned long mfpr_lpm[] = {
>   	MFPR_LPM_PULL_LOW,
>   	MFPR_LPM_PULL_HIGH,
>   	MFPR_LPM_FLOAT,
> +	MFPR_LPM_INPUT,
>   };
>
>   /* mapping of MFP_PULL_* definitions to MFPR_PULL_* register bits */

This adds a bug, which I've been trying to find the right way to fix. 
It's the same case as MFPR_LPM_DEFAULT. Since MFPR_LPM_INPUT = 0, 
MFPR[SLEEP_OE_N] will be cleared at LPM, and the pin will be driven low. 
(Not a good idea for a "default".) Either MFPR_LPM_FLOAT, _PULL_LOW, or 
_PULL_HIGH should be used instead. And only the board code knows enough 
to pick the right one for each pin.

I've been working to cobble together a patch to address this in my
spare time, but don't have U-Boot running on Littleton yet. If you know
of a way to get this going -- or something other way of loading the
kernel -- I'd be grateful for the assist. The difference between blob's 
idea of bad block management vs. Linux's has me avoiding blob at all costs.

-Dave