Re: [U-Boot] [PATCH v3 13/20] Revert: arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

2018-03-09 Thread Maxime Ripard 
Hi,

On Fri, Mar 02, 2018 at 04:24:22PM +, Andre Przywara wrote:
> On 02/03/18 15:58, Maxime Ripard wrote:
> > On Fri, Mar 02, 2018 at 12:56:52AM +, Andre Przywara wrote:
> >> Linux kernels before 4.12-rc1 don't know about the AXP803 PMIC, so can't
> >> enable the MMC driver with the current DT anymore, because that now
> >> depends on this regulator.
> > 
> > Given that only I2C, USB and MMC were supported at the time, is it
> > really worth it? There's a lot of incentive to move to a newer kernel
> > given the minimal support it had at the time.
> 
> Yeah, this is somewhat true, although serial, USB and MMC are somewhat
> enough if one uses a USB Ethernet or WiFi adapter. And the kernel choice
> might not always a decision of the user (thinking of distributions here).
> But I was actually unsure about this as well, and wanted to hear some
> opinions.
> 
> One thing that comes to mind is other OSes. Does anyone know how if for
> instance FreeBSD supports the AXP and its Linux bindings? The whole goal
> of this series is to allow booting OSes with U-Boot's DT copy
> ($fdtcontroladdr), so if this patch would make their life easier, it
> might be worth it.

I thought the DT was only about the hardware (and the firmware to some
extent) and not about a particular implementation?

> Regarding the whole forward/backward compatibility:
> I clearly see the difficulty in coming up with a "perfect" DT from day
> one, especially for badly documented SoCs, where mainlining is driven by
> hobbyists. So I was wondering if we introduce a grace period, where we
> declare the DT "unstable" or "subject to incompatible changes" for some
> releases (not too many). In hindsight we might declare 4.12 the stable
> DT base for the A64, for instance.
> This would allow us to start upstreaming early, with a small feature set
> only (just serial + clocks + pinctrl, as for the H6). Additional
> features (PMIC) might then add small incompatibilities (like this one
> here), until we are reasonably confident about the DT.
> Does that sound useful?

Well, yeah. It's one of reasons I listed when the DT stability was
discussed. I'm glad we reached an agreement on this :)

On a more serious basis, while that would sound reasonable, there's
also the issue that you're basically never done, so that period might
extend indefinitely.

Even on the older SoCs that we first introduce 5 years ago we have to
deal with remodelling the bindings, for mostly three reasons:
  - We have some bindings that we were aware were suboptimal, and the
stability lockdown took us by surprise, and we got stuck with
bindings no one really liked.

  - We have been ignoring some issues for quite some time that will
need to get fixed eventually. For example, the power domains in
the A31 are in this situation: since we didn't have any device
that would allow us to test it, and since we couldn't use the
genpd code for the CPUs in Linux at the time, we don't have any
power domains described. However, there will probably be a time
where we will actually need it for example to deal with the GPU.

  - We are still discovering some quirks that need to remodel the
DT. The DMA bus offset is a good example of that.

For the first one, I guess you could say that it's a bullet we have to
bite. No binding will ever be perfect, and we'll always have to
remodel things as we discover new usecases.

However, the two others are really the one that prevent you from
saying "that's it, we're done" at a particular moment in time.

Maxime

-- 
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Embedded Linux and Kernel engineering
https://bootlin.com


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Re: [U-Boot] [PATCH v3 13/20] Revert: arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

2018-03-04 Thread Emmanuel Vadot 
On Fri, 2 Mar 2018 16:24:22 +
Andre Przywara  wrote:

> Hi,
> 
> On 02/03/18 15:58, Maxime Ripard wrote:
> > On Fri, Mar 02, 2018 at 12:56:52AM +, Andre Przywara wrote:
> >> Linux kernels before 4.12-rc1 don't know about the AXP803 PMIC, so can't
> >> enable the MMC driver with the current DT anymore, because that now
> >> depends on this regulator.
> > 
> > Given that only I2C, USB and MMC were supported at the time, is it
> > really worth it? There's a lot of incentive to move to a newer kernel
> > given the minimal support it had at the time.
> 
> Yeah, this is somewhat true, although serial, USB and MMC are somewhat
> enough if one uses a USB Ethernet or WiFi adapter. And the kernel choice
> might not always a decision of the user (thinking of distributions here).
> But I was actually unsure about this as well, and wanted to hear some
> opinions.
> 
> One thing that comes to mind is other OSes. Does anyone know how if for
> instance FreeBSD supports the AXP and its Linux bindings? The whole goal
> of this series is to allow booting OSes with U-Boot's DT copy
> ($fdtcontroladdr), so if this patch would make their life easier, it
> might be worth it.

 Not yet but I started the work a few days ago and we should have a
driver soon.

> Regarding the whole forward/backward compatibility:
> I clearly see the difficulty in coming up with a "perfect" DT from day
> one, especially for badly documented SoCs, where mainlining is driven by
> hobbyists. So I was wondering if we introduce a grace period, where we
> declare the DT "unstable" or "subject to incompatible changes" for some
> releases (not too many). In hindsight we might declare 4.12 the stable
> DT base for the A64, for instance.
> This would allow us to start upstreaming early, with a small feature set
> only (just serial + clocks + pinctrl, as for the H6). Additional
> features (PMIC) might then add small incompatibilities (like this one
> here), until we are reasonably confident about the DT.
> Does that sound useful?
> 
> So I am not insisting on this patch, but wanted to point out the
> problems that those seemingly innocent DT changes create and would be
> happy if we can at least try to avoid them in the future.
> 
> Cheers,
> Andre.
> ___
> U-Boot mailing list
> U-Boot@lists.denx.de
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Re: [U-Boot] [PATCH v3 13/20] Revert: arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

2018-03-02 Thread Andre Przywara 
Hi,

On 02/03/18 15:58, Maxime Ripard wrote:
> On Fri, Mar 02, 2018 at 12:56:52AM +, Andre Przywara wrote:
>> Linux kernels before 4.12-rc1 don't know about the AXP803 PMIC, so can't
>> enable the MMC driver with the current DT anymore, because that now
>> depends on this regulator.
> 
> Given that only I2C, USB and MMC were supported at the time, is it
> really worth it? There's a lot of incentive to move to a newer kernel
> given the minimal support it had at the time.

Yeah, this is somewhat true, although serial, USB and MMC are somewhat
enough if one uses a USB Ethernet or WiFi adapter. And the kernel choice
might not always a decision of the user (thinking of distributions here).
But I was actually unsure about this as well, and wanted to hear some
opinions.

One thing that comes to mind is other OSes. Does anyone know how if for
instance FreeBSD supports the AXP and its Linux bindings? The whole goal
of this series is to allow booting OSes with U-Boot's DT copy
($fdtcontroladdr), so if this patch would make their life easier, it
might be worth it.

Regarding the whole forward/backward compatibility:
I clearly see the difficulty in coming up with a "perfect" DT from day
one, especially for badly documented SoCs, where mainlining is driven by
hobbyists. So I was wondering if we introduce a grace period, where we
declare the DT "unstable" or "subject to incompatible changes" for some
releases (not too many). In hindsight we might declare 4.12 the stable
DT base for the A64, for instance.
This would allow us to start upstreaming early, with a small feature set
only (just serial + clocks + pinctrl, as for the H6). Additional
features (PMIC) might then add small incompatibilities (like this one
here), until we are reasonably confident about the DT.
Does that sound useful?

So I am not insisting on this patch, but wanted to point out the
problems that those seemingly innocent DT changes create and would be
happy if we can at least try to avoid them in the future.

Cheers,
Andre.
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Re: [U-Boot] [PATCH v3 13/20] Revert: arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

2018-03-02 Thread Maxime Ripard 
On Fri, Mar 02, 2018 at 12:56:52AM +, Andre Przywara wrote:
> Linux kernels before 4.12-rc1 don't know about the AXP803 PMIC, so can't
> enable the MMC driver with the current DT anymore, because that now
> depends on this regulator.

Given that only I2C, USB and MMC were supported at the time, is it
really worth it? There's a lot of incentive to move to a newer kernel
given the minimal support it had at the time.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com


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[U-Boot] [PATCH v3 13/20] Revert: arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

2018-03-01 Thread Andre Przywara 
Linux kernels before 4.12-rc1 don't know about the AXP803 PMIC, so can't
enable the MMC driver with the current DT anymore, because that now
depends on this regulator.
To restore compatiblity with older kernels (where MMC worked fine
without explicit AXP support), restore the former fixed-regulator.
This is no technical disadvantage, as the MMC power rail is actually
VDD-SYS, which drives most of the rest of the board, so can't be turned
off anyway. To underline this, this DCDC1 rail is marked as
"regulator-always-on" in the DT.

This reverts Linux commit 3f241bfa60bdc9c4fde63fa6664a8ce00fd668c6.
Author: Jagan Teki 
Date:   Sat Aug 12 11:10:02 2017 +0530
   arm64: allwinner: a64: pine64: Use dcdc1 regulator for mmc0

Signed-off-by: Andre Przywara 
---
 arch/arm/dts/sun50i-a64-pine64.dts | 9 -
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm/dts/sun50i-a64-pine64.dts 
b/arch/arm/dts/sun50i-a64-pine64.dts
index 604cdaedac..122b5d8e54 100644
--- a/arch/arm/dts/sun50i-a64-pine64.dts
+++ b/arch/arm/dts/sun50i-a64-pine64.dts
@@ -62,6 +62,13 @@
chosen {
stdout-path = "serial0:115200n8";
};
+
+   reg_vcc3v3: vcc3v3 {
+   compatible = "regulator-fixed";
+   regulator-name = "vcc3v3";
+   regulator-min-microvolt = <330>;
+   regulator-max-microvolt = <330>;
+   };
 };
 
  {
@@ -102,7 +109,7 @@
  {
pinctrl-names = "default";
pinctrl-0 = <_pins>;
-   vmmc-supply = <_dcdc1>;
+   vmmc-supply = <_vcc3v3>;
cd-gpios = < 5 6 GPIO_ACTIVE_HIGH>;
cd-inverted;
disable-wp;
-- 
2.14.1

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