[PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Michael Haas]

LDO3 and LDO4 are set to regulator-always-on which causes
crashes on my A20-OLinuXino-LIME2 once axp20x-i2c.ko is loaded.

This crash is observed in combination with recent versions
of Das U-Boot starting from their commit
02cc27c74f9b884b538bcd1b93342a4c05b5d608.

>commit 02cc27c74f9b884b538bcd1b93342a4c05b5d608
>Author: Hans de Goede <hdegoede@redhat.com>
>Date:   Sat Oct 3 15:29:24 2015 +0200
>
>    sunxi: power: Change axp209 LDO3 and LDO4 default to disabled
>
>    LDO3 and LDO4 are normally either unused, or used to power csi
>    attached camera sensors, and as such do not need to be enabled at
>    boot time.
>
>    Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>    Acked-by: Ian Campbell <ijc@hellion.org.uk>

Hans de Goede suggests fixing the Linux DTS file via the u-boot list:

>The regulator-always-on will cause both regulators to get turned on,
>but the min / max constraints match the datasheet constrains / the
>absolute min / max values these ldo-s can deliver, not the constraints
>which the board design puts on these.
>
>So now these ldo-s end up getting turned on at whatever voltage
>is the default (which according to the datasheet is unknown),
>where as the schematic says that if these get turned on (which
>is not necessary) they should be run at 2.8V.
>
>This dts file is the only axp209 using dts file which:
>
>1) Does not have proper constraints for LDO3 / LDO4
>2) Uses regulator-always-on; for these
>
>I would suggest fixing both, first you can try making min = max =
>2800000. And if that fixes things, which I expect it will, I would
>also drop the regulator-always-on from the dts, since we really
>only need to turn these on when using the csi interface in which
>case it would be up to the csi driver to explicitly turn them on.

This patch implements the suggested changes. It is not enough
to set the voltage to 2800000 to avoid the crash. Hence, I have
also removed regulator-always-on.

Signed-off-by: Michael Haas <haas@computerlinguist.org>
CC: Hans de Goede <hdegoede@redhat.com>
---
 arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
index d5c796c..d5ff2e9 100644
--- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
+++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
@@ -140,15 +140,13 @@
 			};
 
 			vcc_csi0: ldo3 {
-				regulator-min-microvolt = <700000>;
-				regulator-max-microvolt = <3500000>;
-				regulator-always-on;
+				regulator-min-microvolt = <2800000>;
+				regulator-max-microvolt = <2800000>;
 			};
 
 			vcc_csi1: ldo4 {
-				regulator-min-microvolt = <1250000>;
-				regulator-max-microvolt = <3300000>;
-				regulator-always-on;
+				regulator-min-microvolt = <2800000>;
+				regulator-max-microvolt = <2800000>;
 			};
 
 			vdd_cpu: dcdc2 {
-- 
2.7.2

[PATCH 2/3] sunxi: A20-OLinuXino-LIME2: Add usb-power-supply

[Michael Haas]

The A20-OLinuXino-LIME2 uses the AXP209 PMIC. This patch adds the
corresponding usb-power-supply node to the DTS.
If CONFIG_AXP20X_POWER is set, this patch enables the /sys/class/power_supply/
diirectory.

Signed-off-by: Michael Haas <haas@computerlinguist.org>
---
 arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
index d5ff2e9..d370166 100644
--- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
+++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
@@ -161,6 +161,9 @@
 				regulator-always-on;
 			};
 		};
+		usb_power_supply: usb_power_supply {
+			compatible = "x-powers,axp202-usb-power-supply";
+		};
 	};
 };
 
-- 
2.7.2

[PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Michael Haas]

The A20 processor provides a third I2C bus on pins PB20 and PB21.
The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.

Olimex also provide a breakout board called the
A20-OLinuXino-LIME2-UEXT. This change is required to properly
support I2C on the UEXT connector found there.

Signed-off-by: Michael Haas <haas@computerlinguist.org>
---
 arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
index d370166..17791ef 100644
--- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
+++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
@@ -179,6 +179,12 @@
 	};
 };
 
+&i2c2 {
+	pinctrl-names = "default";
+	pinctrl-0 = <&i2c2_pins_a>;
+	status = "okay";
+};
+
 &mmc0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&mmc0_pins_a>, <&mmc0_cd_pin_reference_design>;
-- 
2.7.2

[linux-sunxi] [PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Iain Paton]

On 25/03/16 19:04, Michael Haas wrote:
> The A20 processor provides a third I2C bus on pins PB20 and PB21.
> The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.
> 
> Olimex also provide a breakout board called the
> A20-OLinuXino-LIME2-UEXT. This change is required to properly
> support I2C on the UEXT connector found there.
> 
> Signed-off-by: Michael Haas <haas@computerlinguist.org>

Acked-by: Iain Paton <ipaton0@gmail.com>

This didn't go in originally simply because not everyone will have 
the breakout and they may want to use those pins for other things.

[linux-sunxi] [PATCH 2/3] sunxi: A20-OLinuXino-LIME2: Add usb-power-supply

[Iain Paton]

On 25/03/16 19:04, Michael Haas wrote:
> The A20-OLinuXino-LIME2 uses the AXP209 PMIC. This patch adds the
> corresponding usb-power-supply node to the DTS.
> If CONFIG_AXP20X_POWER is set, this patch enables the /sys/class/power_supply/
> diirectory.
> 
> Signed-off-by: Michael Haas <haas@computerlinguist.org>

Acked-by: Iain Paton <ipaton0@gmail.com>

[linux-sunxi] [PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Iain Paton]

On 25/03/16 19:04, Michael Haas wrote:

> This patch implements the suggested changes. It is not enough
> to set the voltage to 2800000 to avoid the crash. Hence, I have
> also removed regulator-always-on.

NAK.

If setting both min and max to 2800000 isn't working then I'd suggest you're 
just papering over the issue and not actually solving it.

It should be fairly clear that whenever those regulators are turned on by 
some driver you're going to see the same issue, you've just delayed the 
problem by removing the regulator-always-on item.

The real problem here is people monkeying with the regulators without 
understanding what they're doing, bothering to test the results, or caring 
about the consequences.

Anyway, Hans was correct in that the datasheet we have access to says that 
the defaults for these regulators are undefined. 
I suspect that's not the whole story though, if these regulators had random 
values at powerup we'd have seen problems before now. 
Most likely the values we think we know are simply incorrect plus there's 
probably some element of sequencing involved - perhaps LDO4 needs turned on 
first. 
However I don't see sufficient detail in the datasheets to confirm any of 
that, so we shouldn't assume anything.
Electrically on the lime2 LDO3 goes to VCC-PE and LDO4 to VCC-PG. Neither 
groups E or G appear to be connected to anything other than gpio headers, 
so this has little to do with board design, it's something internal to 
the SoC that the datasheet is lacking on detail about.

One of the reasons for the regulator-always-on being in the dts was so that 
the regulator didn't get touched and so didn't break anything.

All said and done, it only takes a minute with a multimeter to determine 
actual defaults. Helpful to have multiple boards to gain some confidence 
that they behave the same, but still basing values like this on tiny 
sample sizes is probably unwise.

Looking at other A20 based boards, Cubieboards for example, shows LDO3/4 
being unused and the VCC-PE/PG pins they power on the lime2 being tied 
directly to 3.3v. No issues there simply because there's no way to mess 
with the power to those blocks.

The patch you really want is something like the one below which works 
on my boards regardless of the presence of regulator-always-on.
Verified on four boards with u-boot 2016.03 and kernel 4.5.0.

Whether you decide to remove regulator-always-on or not is a different 
question, but please use 2.3v, or some other proven working value, for 
ldo3. At least that way you have a fighting chance of the board 
remaining functional when something wants to turn the regulator on.

It's a good bet that the same u-boot change will have implications 
for other boards, if not now then at some future point.

Hans, take note, the schematic is wrong. You shouldn't assume either 
the schematic or you are correct. Ill considered changes to regulators 
can cause real damage to peoples boards.
I know we've discussed regulators before and that my opinion falls on 
deaf ears, but worth one last try..



Author: Iain Paton <ipaton0@gmail.com>
Date:   Fri Mar 25 22:07:55 2016 +0000

sunxi: A20-OLinuXino-LIME2: Update ldo3/ldo4 in DTS

A recent ill-considered u-boot change:

>commit 02cc27c74f9b884b538bcd1b93342a4c05b5d608
>Author: Hans de Goede <hdegoede@redhat.com>
>Date:   Sat Oct 3 15:29:24 2015 +0200
>
>    sunxi: power: Change axp209 LDO3 and LDO4 default to disabled

causes the lime2 to lockup/crash when LDO3/4 are re-enabled by the
kernel.

The AXP209 datasheet shows the powerup values for these regulators 
to be undefined and the 2.8v suggested by the lime2 schematic also 
causes a lockup when the regulators are re-enabled so is obviously 
also incorrect.

Empirical measurement suggests LDO3 @ 2.3v and LDO4 @ 2.8v are the 
actual defaults, but is based on a small sample size. 

Verified to work with u-boot 2016.03, kernel 4.5.0 on four lime2 
boards.

Signed-off-by: Iain Paton <ipaton0@gmail.com>
---

diff --git a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
index d5c796c..e665d22 100644
--- a/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
+++ b/arch/arm/boot/dts/sun7i-a20-olinuxino-lime2.dts
@@ -140,14 +140,14 @@
                        };
 
                        vcc_csi0: ldo3 {
-                               regulator-min-microvolt = <700000>;
-                               regulator-max-microvolt = <3500000>;
+                               regulator-min-microvolt = <2300000>;
+                               regulator-max-microvolt = <2300000>;
                                regulator-always-on;
                        };
 
                        vcc_csi1: ldo4 {
-                               regulator-min-microvolt = <1250000>;
-                               regulator-max-microvolt = <3300000>;
+                               regulator-min-microvolt = <2800000>;
+                               regulator-max-microvolt = <2800000>;
                                regulator-always-on;
                        };
 
-- 

[linux-sunxi] [PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Iain Paton]

Having reread the A20 datasheet yesterday, something in the back of my 
mind was bothering me overnight so I took some time to check this morning.

On the lime2 schematic we see the pins labeled as follows:

F19 : VCC_CSI0
E18 : VCC_CSI1

However the A20 datasheet doesn't label them this way, instead using:

F19 : VCC-PE : Port E Power Supply
E18 : VCC-PG : Port G Power Supply

no mention at all of CSI. CSI just happens to be a function that can be 
multiplexed onto ports E & G.

So lets assume for a moment we don't have a CSI device, or a CSI driver 
and are not using those pins for CSI functions but are instead using 
their default GPIO purpose, or in the case of PG perhaps for UART3 
or UART4.

What happens when you disable the regulator?  Hopefully from the above 
you'll already have worked out that you lose ports E & G when you turn 
their I/O power supply off and anything multiplexed onto those ports 
becomes unuseable.

I haven't checked other schematics, but all of the Olimex A10/A20 
boards along with Cubieboard & CubieTruck label these pins as VCC_CSIn
It would be my guess that there's a reference design being given to 
manufacturers, perhaps the original Cubieboard even, that makes this 
mistake and everyone else has blindly copied it.

So, unless we want to lose access to 24 GPIO pins for no real reason 
I'd suggest that the u-boot patch is reverted and/or the dts is altered 
such that the gpio driver claims the regulators and prevents them being 
turned off.

The u-boot commit message and reasoning given on list are trivially 
proved incorrect. Ports E & G are not CSI-only, losing all other 
functions on these ports is not acceptable.

I've also just tested building u-boot with LDO3 & 4 voltages set to 
3.3v to be the same as CubieBoard, this works for lime2.
So it's unlikely that the 2.8v & 2.3v settings from my previous patch 
make sense. The crash is actually being caused by something else, 
probably sequencing, due to unnecessarily turning the regulators off.
Whatever the reason, we don't have enough information in the 
datasheets to know for sure so we simply shouldn't turn them off to 
begin with.

The people behind this need to take responsibility and clean up their 
mess.

Iain

[linux-sunxi] [PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Michael Haas]

On 03/26/2016 09:56 AM, Iain Paton wrote:
> Having reread the A20 datasheet yesterday, something in the back of my 
> mind was bothering me overnight so I took some time to check this morning.
>
> On the lime2 schematic we see the pins labeled as follows:
>
> F19 : VCC_CSI0
> E18 : VCC_CSI1
>
> However the A20 datasheet doesn't label them this way, instead using:
>
> F19 : VCC-PE : Port E Power Supply
> E18 : VCC-PG : Port G Power Supply
>
> no mention at all of CSI. CSI just happens to be a function that can be 
> multiplexed onto ports E & G.
>
> So lets assume for a moment we don't have a CSI device, or a CSI driver 
> and are not using those pins for CSI functions but are instead using 
> their default GPIO purpose, or in the case of PG perhaps for UART3 
> or UART4.
>
> What happens when you disable the regulator?  Hopefully from the above 
> you'll already have worked out that you lose ports E & G when you turn 
> their I/O power supply off and anything multiplexed onto those ports 
> becomes unuseable.
>

Hi Iain,

I took some time to go through the data sheets and your analysis is on
point.

I did raise an issue with Olimex via github [0]. Maybe they will update
their schematics.


I do have my breakout board connected to GPIO-1.. and it turns out that
mostly port G is exposed on GPIO-1. I'll be reverting Hans' patch locally
so I can toggle some pins today. I am sure he will contribute his own
thoughts on the matter.


> I've also just tested building u-boot with LDO3 & 4 voltages set to 
> 3.3v to be the same as CubieBoard, this works for lime2.
> So it's unlikely that the 2.8v & 2.3v settings from my previous patch 
> make sense. The crash is actually being caused by something else, 
> probably sequencing, due to unnecessarily turning the regulators off.
> Whatever the reason, we don't have enough information in the 
> datasheets to know for sure so we simply shouldn't turn them off to 
> begin with.


I just tried that on linux and axp20x-regulator.ko refuses to set the
voltage
on ldo4:

[   88.914653] at24 1-0050: 2048 byte 24c16 EEPROM, writable, 16 bytes/write
[   96.893312] axp20x-i2c 0-0034: AXP20x variant AXP209 found
[   96.910631] axp20x-i2c 0-0034: AXP20X driver loaded
[   96.955579] input: axp20x-pek as
/devices/platform/soc at 01c00000/1c2ac00.i2c/i2c-0/0-0034/axp20x-pek/input/input0
[   96.971734] ldo4: failed to apply 3300000uV constraint(-22)
[   96.990646] axp20x-regulator axp20x-regulator: Failed to register ldo4
[   97.012686] axp20x-regulator: probe of axp20x-regulator failed with
error -22

Perhaps this requires another patch [1], but unless there's a real need
for me to verify this,
I'll simply revert the u-boot patch and enjoy working GPIO.

Michael

[0] https://github.com/OLIMEX/OLINUXINO/issues/35
[1] https://www.spinics.net/lists/devicetree/msg118871.html

[linux-sunxi] [PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Hans de Goede]

Hi,

On 27-03-16 10:08, Michael Haas wrote:
> On 03/26/2016 09:56 AM, Iain Paton wrote:
>> Having reread the A20 datasheet yesterday, something in the back of my
>> mind was bothering me overnight so I took some time to check this morning.
>>
>> On the lime2 schematic we see the pins labeled as follows:
>>
>> F19 : VCC_CSI0
>> E18 : VCC_CSI1
>>
>> However the A20 datasheet doesn't label them this way, instead using:
>>
>> F19 : VCC-PE : Port E Power Supply
>> E18 : VCC-PG : Port G Power Supply
>>
>> no mention at all of CSI. CSI just happens to be a function that can be
>> multiplexed onto ports E & G.
>>
>> So lets assume for a moment we don't have a CSI device, or a CSI driver
>> and are not using those pins for CSI functions but are instead using
>> their default GPIO purpose, or in the case of PG perhaps for UART3
>> or UART4.
>>
>> What happens when you disable the regulator?  Hopefully from the above
>> you'll already have worked out that you lose ports E & G when you turn
>> their I/O power supply off and anything multiplexed onto those ports
>> becomes unuseable.
>>
>
> Hi Iain,
>
> I took some time to go through the data sheets and your analysis is on
> point.
>
> I did raise an issue with Olimex via github [0]. Maybe they will update
> their schematics.
>
>
> I do have my breakout board connected to GPIO-1.. and it turns out that
> mostly port G is exposed on GPIO-1. I'll be reverting Hans' patch locally
> so I can toggle some pins today. I am sure he will contribute his own
> thoughts on the matter.
>
>
>> I've also just tested building u-boot with LDO3 & 4 voltages set to
>> 3.3v to be the same as CubieBoard, this works for lime2.
>> So it's unlikely that the 2.8v & 2.3v settings from my previous patch
>> make sense. The crash is actually being caused by something else,
>> probably sequencing, due to unnecessarily turning the regulators off.
>> Whatever the reason, we don't have enough information in the
>> datasheets to know for sure so we simply shouldn't turn them off to
>> begin with.
>
>
> I just tried that on linux and axp20x-regulator.ko refuses to set the
> voltage
> on ldo4:
>
> [   88.914653] at24 1-0050: 2048 byte 24c16 EEPROM, writable, 16 bytes/write
> [   96.893312] axp20x-i2c 0-0034: AXP20x variant AXP209 found
> [   96.910631] axp20x-i2c 0-0034: AXP20X driver loaded
> [   96.955579] input: axp20x-pek as
> /devices/platform/soc at 01c00000/1c2ac00.i2c/i2c-0/0-0034/axp20x-pek/input/input0
> [   96.971734] ldo4: failed to apply 3300000uV constraint(-22)
> [   96.990646] axp20x-regulator axp20x-regulator: Failed to register ldo4
> [   97.012686] axp20x-regulator: probe of axp20x-regulator failed with
> error -22
>
> Perhaps this requires another patch [1],

Yes setting the constraints to 3.3v requires the patch you link for things to work.

> but unless there's a real need
> for me to verify this,
> I'll simply revert the u-boot patch and enjoy working GPIO.

Given the entire discussion in this thread, I agree that fixing this in u-boot
is best. But I do not see reverting the u-boot patch disabling ldo3/4 by default
as the solution. ldo3/4 are unused on most boards, so disabling them by default
clearly is the right thing todo IMHO.

Instead please submit a patch for configs/A20-OLinuXino-Lime2_defconfig which
configures them at 2800 mV there (per the Lime2 schematic).

It would be good to also check the Lime1 schematic if they are used in the same
way there, I would also welcome a patch for:

configs/A10-OLinuXino-Lime_defconfig
configs/A20-OLinuXino-Lime_defconfig

Regards,

Hans

[linux-sunxi] [PATCH 1/3] sunxi: A20-OLinuXino-LIME2: Fix ldo3/ldo4 in DTS

[Maxime Ripard]

On Mon, Mar 28, 2016 at 03:01:27PM +0200, Hans de Goede wrote:
> >but unless there's a real need
> >for me to verify this,
> >I'll simply revert the u-boot patch and enjoy working GPIO.
> 
> Given the entire discussion in this thread, I agree that fixing this in u-boot
> is best. But I do not see reverting the u-boot patch disabling ldo3/4 by default
> as the solution. ldo3/4 are unused on most boards, so disabling them by default
> clearly is the right thing todo IMHO.
> 
> Instead please submit a patch for configs/A20-OLinuXino-Lime2_defconfig which
> configures them at 2800 mV there (per the Lime2 schematic).
> 
> It would be good to also check the Lime1 schematic if they are used in the same
> way there, I would also welcome a patch for:
> 
> configs/A10-OLinuXino-Lime_defconfig
> configs/A20-OLinuXino-Lime_defconfig

Adding a comment to the DT summing up that whole discussion would be
great too.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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[PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Maxime Ripard]

Hi,

On Fri, Mar 25, 2016 at 08:04:07PM +0100, Michael Haas wrote:
> The A20 processor provides a third I2C bus on pins PB20 and PB21.
> The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.
> 
> Olimex also provide a breakout board called the
> A20-OLinuXino-LIME2-UEXT. This change is required to properly
> support I2C on the UEXT connector found there.
> 
> Signed-off-by: Michael Haas <haas@computerlinguist.org>

What are the other options on that pin? Is it something exclusively
dedicated to i2c on the pin headers and the documentation, or is
anyone free to use that pin for whatever he wishes?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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[PATCH 2/3] sunxi: A20-OLinuXino-LIME2: Add usb-power-supply

[Maxime Ripard]

Hi,

On Fri, Mar 25, 2016 at 08:04:06PM +0100, Michael Haas wrote:
> The A20-OLinuXino-LIME2 uses the AXP209 PMIC. This patch adds the
> corresponding usb-power-supply node to the DTS.
> If CONFIG_AXP20X_POWER is set, this patch enables the /sys/class/power_supply/
> diirectory.
> 
> Signed-off-by: Michael Haas <haas@computerlinguist.org>

Is there *any* reason to not use the AXP209 dtsi where it's already
defined?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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[linux-sunxi] Re: [PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Priit Laes]

On Sat, 2016-04-02 at 12:34 +0200, Maxime Ripard wrote:
> Hi,
> 
> On Fri, Mar 25, 2016 at 08:04:07PM +0100, Michael Haas wrote:
> > 
> > The A20 processor provides a third I2C bus on pins PB20 and PB21.
> > The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.
> > 
> > Olimex also provide a breakout board called the
> > A20-OLinuXino-LIME2-UEXT. This change is required to properly
> > support I2C on the UEXT connector found there.

Documentation for Olimex UEXT interface:
https://www.olimex.com/Products/Modules/UEXT/resources/UEXT_rev_B.pdf

Basically it *should* by default work as a board to board connector
which supports three serial communication interfaces: I2C, SPI and UART
(original document mentions RS232, but official modules work only with
3.3V logic levels).

> > 
> > Signed-off-by: Michael Haas <haas@computerlinguist.org>
> What are the other options on that pin? Is it something exclusively
> dedicated to i2c on the pin headers and the documentation, or is
> anyone free to use that pin for whatever he wishes?
> 
> Thanks,
> Maxime
> 
> --?
> Maxime Ripard, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com
> 

[linux-sunxi] Re: [PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Michael Haas]

Hello Maxime,

thank you for taking the time to review this patch set.

On 04/02/2016 12:34 PM, Maxime Ripard wrote:
> Hi,
>
> On Fri, Mar 25, 2016 at 08:04:07PM +0100, Michael Haas wrote:
>> The A20 processor provides a third I2C bus on pins PB20 and PB21.
>> The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.
>>
>> Olimex also provide a breakout board called the
>> A20-OLinuXino-LIME2-UEXT. This change is required to properly
>> support I2C on the UEXT connector found there.
>>
>> Signed-off-by: Michael Haas <haas@computerlinguist.org>
>
> What are the other options on that pin? Is it something exclusively
> dedicated to i2c on the pin headers and the documentation, or is
> anyone free to use that pin for whatever he wishes?
>
> Thanks,
> Maxime

I assume you are talking about the UEXT connector, not about PB20 and
PB21. These are regular GPIO pins multiplexed with I2C, but no other
function.

Regarding UEXT: the A20-OLinuXino-LIME2-UEXT breakout board supports two
use cases here.

The first one: provide a simple adapter from the 0.05" pin headers on
the olinuxino to the more common world of 0.1" headers. In this use
case, you can plug the A20-OLinuXino-LIME2-UEXT intoany of LCD_CON or
GIO-{1,2,3} and you're good to go.

The second one: here, you want to use UEXT modules provided by Olimex.
It's a simple connector exposing I2C, SPI and UART as mentioned by
Priit. To use UEXT, you have to use GPIO-1 to get the correct pin mapping.

Regarding the official documentation provided by Olimex. The
A20-OLinuXino-Lime2_Rev_c.pdf shows the pins on GPIO-1 as PB20 and PB21.
In the schematics for the breakout board,
A20-OLinuXino-Lime2-UEXT_sch.pdf, the pins for the UEXT connector are
labeled as PB20/SCK and PB21/SDA. This acknowledges the double use.
However, PB20 and PB21 have pull-ups by default according to
A20-OLinuXino-Lime2_Rev_c.pdf,
which makes them a lot more useful as I2C than as GPIO.

What originally prompted me to submit this patch: I bought a breakout
board and a small LCD with UEXT connector together with my board. Then I
found out that it doesn't work out of the box because i2c2 is not
enabled. Since using UEXT is probably common for that particular
vendor, I believe it should be enabled by default.

Michael

[linux-sunxi] Re: [PATCH 3/3] sunxi: A20-OLinuXino-LIME2: Add i2c2 bus in DTS

[Maxime Ripard]

Hi Michael,

On Sat, Apr 02, 2016 at 06:21:17PM +0200, Michael Haas wrote:
> Hello Maxime,
> 
> thank you for taking the time to review this patch set.
> 
> On 04/02/2016 12:34 PM, Maxime Ripard wrote:
> > Hi,
> >
> > On Fri, Mar 25, 2016 at 08:04:07PM +0100, Michael Haas wrote:
> >> The A20 processor provides a third I2C bus on pins PB20 and PB21.
> >> The A20-OLinuXino-LIME2 exposes this bus via its GPIO1 port.
> >>
> >> Olimex also provide a breakout board called the
> >> A20-OLinuXino-LIME2-UEXT. This change is required to properly
> >> support I2C on the UEXT connector found there.
> >>
> >> Signed-off-by: Michael Haas <haas@computerlinguist.org>
> >
> > What are the other options on that pin? Is it something exclusively
> > dedicated to i2c on the pin headers and the documentation, or is
> > anyone free to use that pin for whatever he wishes?
> >
> > Thanks,
> > Maxime
> 
> I assume you are talking about the UEXT connector, not about PB20 and
> PB21. These are regular GPIO pins multiplexed with I2C, but no other
> function.
> 
> Regarding UEXT: the A20-OLinuXino-LIME2-UEXT breakout board supports two
> use cases here.
> 
> The first one: provide a simple adapter from the 0.05" pin headers on
> the olinuxino to the more common world of 0.1" headers. In this use
> case, you can plug the A20-OLinuXino-LIME2-UEXT intoany of LCD_CON or
> GIO-{1,2,3} and you're good to go.
> 
> The second one: here, you want to use UEXT modules provided by Olimex.
> It's a simple connector exposing I2C, SPI and UART as mentioned by
> Priit. To use UEXT, you have to use GPIO-1 to get the correct pin mapping.
> 
> Regarding the official documentation provided by Olimex. The
> A20-OLinuXino-Lime2_Rev_c.pdf shows the pins on GPIO-1 as PB20 and PB21.
> In the schematics for the breakout board,
> A20-OLinuXino-Lime2-UEXT_sch.pdf, the pins for the UEXT connector are
> labeled as PB20/SCK and PB21/SDA. This acknowledges the double use.
> However, PB20 and PB21 have pull-ups by default according to
> A20-OLinuXino-Lime2_Rev_c.pdf,
> which makes them a lot more useful as I2C than as GPIO.

Thanks for the explanation.

> What originally prompted me to submit this patch: I bought a breakout
> board and a small LCD with UEXT connector together with my board. Then I
> found out that it doesn't work out of the box because i2c2 is not
> enabled. Since using UEXT is probably common for that particular
> vendor, I believe it should be enabled by default.

Unfortunately, if it isn't present on the main board, it shouldn't be
in the DT for that board. Otherwise, people relying on these pins and
not using the UEXT connector would be force fed a configuration that
they don't want, without any way to remove it.

That kind of adjustements is a perfect use case for the overlays
though, so I'd rather suggest writing one for the UEXT connector.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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[linux-sunxi] Re: [PATCH 2/3] sunxi: A20-OLinuXino-LIME2: Add usb-power-supply

[Michael Haas]

Hi Maxime,


On 04/02/2016 12:36 PM, Maxime Ripard wrote:
> Hi,
> 
> On Fri, Mar 25, 2016 at 08:04:06PM +0100, Michael Haas wrote:
>> The A20-OLinuXino-LIME2 uses the AXP209 PMIC. This patch adds the
>> corresponding usb-power-supply node to the DTS.
>> If CONFIG_AXP20X_POWER is set, this patch enables the /sys/class/power_supply/
>> diirectory.
>>
>> Signed-off-by: Michael Haas <haas@computerlinguist.org>
> 
> Is there *any* reason to not use the AXP209 dtsi where it's already
> defined?
> 

do you have any preference for this being in the AXP209 dtsi? I've been
thinking about it and it makes sense to enable the power supply nodes
for all devices using the AXP209. They will just report themselves as
offline if the PMIC indicates nothing is connected.

Best,

Michael


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[linux-sunxi] Re: [PATCH 2/3] sunxi: A20-OLinuXino-LIME2: Add usb-power-supply

[Maxime Ripard]

On Sun, May 01, 2016 at 08:46:28AM +0200, Michael Haas wrote:
> Hi Maxime,
> 
> 
> On 04/02/2016 12:36 PM, Maxime Ripard wrote:
> > Hi,
> > 
> > On Fri, Mar 25, 2016 at 08:04:06PM +0100, Michael Haas wrote:
> >> The A20-OLinuXino-LIME2 uses the AXP209 PMIC. This patch adds the
> >> corresponding usb-power-supply node to the DTS.
> >> If CONFIG_AXP20X_POWER is set, this patch enables the /sys/class/power_supply/
> >> diirectory.
> >>
> >> Signed-off-by: Michael Haas <haas@computerlinguist.org>
> > 
> > Is there *any* reason to not use the AXP209 dtsi where it's already
> > defined?
> > 
> 
> do you have any preference for this being in the AXP209 dtsi? I've been
> thinking about it and it makes sense to enable the power supply nodes
> for all devices using the AXP209. They will just report themselves as
> offline if the PMIC indicates nothing is connected.

Yes, I'd prefer that a lot :)

It avoids enabling it on all the boards.

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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