Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Tony Lindgren]

* Tony Lindgren  [151201 17:23]:
> * Matthijs van Duin  [151201 17:15]:
> > On 2 December 2015 at 01:46, Tony Lindgren  wrote:
> > > Ouch. We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
> > > dts macros that ensure that?
> > 
> > Can't we just keep bit 18 out of the function mask? The bootloader
> > should already have made sure all pins have bit 18 set (and bit 19 set
> > to correct values after ROM mucked them up, see advisory 2.1.88), so
> > all that needs to be done is avoid touching them.
> 
> Sounds good to me. And people who really want to override the mask can
> do it in the board specifc dts file.
> 
> > Are the power savings from disabling unnecessary inputs significant
> > enough to spend any headache on it?
> 
> Only for some battery powered devices, not in this case for sure.

And here's an updated version of this patch.

Regards,

Tony

8< 
From: Tony Lindgren 
Date: Tue, 1 Dec 2015 15:04:38 -0800
Subject: [PATCH] ARM: dts: Fix dm814x pinctrl address and mask

Otherwise pinctrl won't work. Because of silicon errata for some dm814x
versions, let's also keep bit 18 out of the function-mask and rely on
the bootloader configuration for bit 18  as suggested by
Matthijs van Duin .

Devices with that need to use bit 18 can override the function-mask in
the board specific dts file if really needed.

Signed-off-by: Tony Lindgren 

--- a/arch/arm/boot/dts/dm814x.dtsi
+++ b/arch/arm/boot/dts/dm814x.dtsi
@@ -205,13 +205,21 @@
};
};
 
+   /*
+* Note that silicon revision 2.1 and older
+* require input enabled (bit 18 set) for all
+* 3.3V I/Os to avoid cumulative hardware 
damage.
+* For more info, see errata advisory 2.1.87.
+* We leave bit 18 out of function-mask and rely
+* on the bootloader for it.
+*/
pincntl: pinmux@800 {
compatible = "pinctrl-single";
-   reg = <0x800 0xc38>;
+   reg = <0x800 0x438>;
#address-cells = <1>;
#size-cells = <0>;
pinctrl-single,register-width = <32>;
-   pinctrl-single,function-mask = 
<0x300ff>;
+   pinctrl-single,function-mask = 
<0x307ff>;
};
};
 
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Tony Lindgren]

* Matthijs van Duin  [151201 17:23]:
> On 2 December 2015 at 01:46, Tony Lindgren  wrote:
> > We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
> > dts macros that ensure that?
> 
> I'm in general no fan of such macros: it feels really awkward to have
> to make that distinction in dts when doing pin config.
> 
> Note that if you're feeling really enthausiastic about putting in
> effort to allow inputs to be disabled while staying clear of the
> erratum, I think you can detect at runtime which I/O supplies are 3.3V
> by inspecting this register:
> 
> #define CTRL_CQDETECT_STATUS0x48140e00

OK and if really needed needed the SoC revision information can be
passed to pinctrl-singl.c in it's platform_data that we already have
in addition to the dts configuration. And then pinctrl-single.c could
modify the mask based on IO voltage and SoC revision.

I think we're already covered as the boards can override the pinctrl
function-mask in the board specific dts file if really needed :)

Regards,

Tony
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Tony Lindgren]

* Matthijs van Duin  [151201 16:26]:
> On 2 December 2015 at 00:38, Tony Lindgren  wrote:
> > -   pinctrl-single,function-mask = 
> > <0x300ff>;
> > +   pinctrl-single,function-mask = 
> > <0x707ff>;
> 
> Reminder that silicon revision 2.1 and older require input enabled
> (bit 18 set) for all 3.3V I/Os to avoid cumulative hardware damage.
> (Errata advisory 2.1.87)

Ouch. We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
dts macros that ensure that?

Regards,

Tony
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Matthijs van Duin]

On 2 December 2015 at 00:38, Tony Lindgren  wrote:
> -   pinctrl-single,function-mask = 
> <0x300ff>;
> +   pinctrl-single,function-mask = 
> <0x707ff>;

Reminder that silicon revision 2.1 and older require input enabled
(bit 18 set) for all 3.3V I/Os to avoid cumulative hardware damage.
(Errata advisory 2.1.87)
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Matthijs van Duin]

On 2 December 2015 at 01:46, Tony Lindgren  wrote:
> Ouch. We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
> dts macros that ensure that?

Can't we just keep bit 18 out of the function mask? The bootloader
should already have made sure all pins have bit 18 set (and bit 19 set
to correct values after ROM mucked them up, see advisory 2.1.88), so
all that needs to be done is avoid touching them.

Are the power savings from disabling unnecessary inputs significant
enough to spend any headache on it?

Matthijs
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Matthijs van Duin]

On 2 December 2015 at 01:46, Tony Lindgren  wrote:
> We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
> dts macros that ensure that?

I'm in general no fan of such macros: it feels really awkward to have
to make that distinction in dts when doing pin config.

Note that if you're feeling really enthausiastic about putting in
effort to allow inputs to be disabled while staying clear of the
erratum, I think you can detect at runtime which I/O supplies are 3.3V
by inspecting this register:

#define CTRL_CQDETECT_STATUS0x48140e00

Matthijs
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Re: [PATCH 10/10] ARM: dts: Fix dm814x pinctrl address and mask

[Tony Lindgren]

* Matthijs van Duin  [151201 17:15]:
> On 2 December 2015 at 01:46, Tony Lindgren  wrote:
> > Ouch. We should probably have separate PIN_INPUT_3V3 and PIN_OUTPUT_3V3
> > dts macros that ensure that?
> 
> Can't we just keep bit 18 out of the function mask? The bootloader
> should already have made sure all pins have bit 18 set (and bit 19 set
> to correct values after ROM mucked them up, see advisory 2.1.88), so
> all that needs to be done is avoid touching them.

Sounds good to me. And people who really want to override the mask can
do it in the board specifc dts file.

> Are the power savings from disabling unnecessary inputs significant
> enough to spend any headache on it?

Only for some battery powered devices, not in this case for sure.

Regards,.

Tony
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