[PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[Paul Cercueil]

Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
names") caused the VDDCORE power supply (regulated by the ACT8600's
DCDC1 output) to drop from a voltage of 1.2V configured by the
bootloader, to the 1.1V set in the Device Tree.

According to the documentation, the VDDCORE supply should be between
0.99V and 1.21V; both values are therefore within the supported range.

However, VDDCORE being 1.1V results in the CI20 being very unstable,
with corrupted memory, failures to boot, or reboots at random. The
reason might be succint drops of the voltage below the minimum required.

Raising the minimum voltage to 1.125 volts seems to be enough to address
this issue, while still keeping a relatively low core voltage which
helps for power consumption and thermals.

Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node names")
Signed-off-by: Paul Cercueil <paul@crapouillou.net>

---
Cc: H. Nikolaus Schaller <hns@goldelico.com>
---
 arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/boot/dts/ingenic/ci20.dts b/arch/mips/boot/dts/ingenic/ci20.dts
index cec0caa2350c..a141a699b790 100644
--- a/arch/mips/boot/dts/ingenic/ci20.dts
+++ b/arch/mips/boot/dts/ingenic/ci20.dts
@@ -298,8 +298,8 @@ act8600: act8600@5a {
 
 		regulators {
 			vddcore: DCDC1 {
-				regulator-min-microvolt = <1100000>;
-				regulator-max-microvolt = <1100000>;
+				regulator-min-microvolt = <1125000>;
+				regulator-max-microvolt = <1125000>;
 				vp1-supply = <&vcc_33v>;
 				regulator-always-on;
 			};
-- 
2.40.1

Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[Thomas Bogendoerfer]

On Thu, Jun 22, 2023 at 07:59:34PM +0200, Paul Cercueil wrote:
> Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
> names") caused the VDDCORE power supply (regulated by the ACT8600's
> DCDC1 output) to drop from a voltage of 1.2V configured by the
> bootloader, to the 1.1V set in the Device Tree.
> 
> According to the documentation, the VDDCORE supply should be between
> 0.99V and 1.21V; both values are therefore within the supported range.
> 
> However, VDDCORE being 1.1V results in the CI20 being very unstable,
> with corrupted memory, failures to boot, or reboots at random. The
> reason might be succint drops of the voltage below the minimum required.
> 
> Raising the minimum voltage to 1.125 volts seems to be enough to address
> this issue, while still keeping a relatively low core voltage which
> helps for power consumption and thermals.
> 
> Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node names")
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> 
> ---
> Cc: H. Nikolaus Schaller <hns@goldelico.com>
> ---
>  arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/boot/dts/ingenic/ci20.dts b/arch/mips/boot/dts/ingenic/ci20.dts
> index cec0caa2350c..a141a699b790 100644
> --- a/arch/mips/boot/dts/ingenic/ci20.dts
> +++ b/arch/mips/boot/dts/ingenic/ci20.dts
> @@ -298,8 +298,8 @@ act8600: act8600@5a {
>  
>  		regulators {
>  			vddcore: DCDC1 {
> -				regulator-min-microvolt = <1100000>;
> -				regulator-max-microvolt = <1100000>;
> +				regulator-min-microvolt = <1125000>;
> +				regulator-max-microvolt = <1125000>;
>  				vp1-supply = <&vcc_33v>;
>  				regulator-always-on;
>  			};
> -- 
> 2.40.1

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[H. Nikolaus Schaller]

Hi Thomas,
you are again too fast. Please let people enough time to test and comment patches.

I have started ca. 1 hour ago to do more tests on this topic and am currently in the middle of testing this.

At the moment it looks as if I would recommend not to apply it now. Since I have no problems with 1.10V with the letux-os distribution kernel (which adds some other patches and uses a different defconfig) but only with upstream and ci20_defconfig. So a proper solution may be completely different.

Best regards,
Nikolaus


> Am 23.06.2023 um 15:09 schrieb Thomas Bogendoerfer <tsbogend@alpha.franken.de>:
> 
> On Thu, Jun 22, 2023 at 07:59:34PM +0200, Paul Cercueil wrote:
>> Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
>> names") caused the VDDCORE power supply (regulated by the ACT8600's
>> DCDC1 output) to drop from a voltage of 1.2V configured by the
>> bootloader, to the 1.1V set in the Device Tree.
>> 
>> According to the documentation, the VDDCORE supply should be between
>> 0.99V and 1.21V; both values are therefore within the supported range.
>> 
>> However, VDDCORE being 1.1V results in the CI20 being very unstable,
>> with corrupted memory, failures to boot, or reboots at random. The
>> reason might be succint drops of the voltage below the minimum required.
>> 
>> Raising the minimum voltage to 1.125 volts seems to be enough to address
>> this issue, while still keeping a relatively low core voltage which
>> helps for power consumption and thermals.
>> 
>> Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node names")
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> 
>> ---
>> Cc: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/arch/mips/boot/dts/ingenic/ci20.dts b/arch/mips/boot/dts/ingenic/ci20.dts
>> index cec0caa2350c..a141a699b790 100644
>> --- a/arch/mips/boot/dts/ingenic/ci20.dts
>> +++ b/arch/mips/boot/dts/ingenic/ci20.dts
>> @@ -298,8 +298,8 @@ act8600: act8600@5a {
>> 
>> 		regulators {
>> 			vddcore: DCDC1 {
>> -				regulator-min-microvolt = <1100000>;
>> -				regulator-max-microvolt = <1100000>;
>> +				regulator-min-microvolt = <1125000>;
>> +				regulator-max-microvolt = <1125000>;
>> 				vp1-supply = <&vcc_33v>;
>> 				regulator-always-on;
>> 			};
>> -- 
>> 2.40.1
> 
> applied to mips-next.
> 
> Thomas.
> 
> -- 
> Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
> good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[H. Nikolaus Schaller]

Hi Paul, Thomas,
here are my test results.

> Am 22.06.2023 um 19:59 schrieb Paul Cercueil <paul@crapouillou.net>:
> 
> Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
> names") caused the VDDCORE power supply (regulated by the ACT8600's
> DCDC1 output) to drop from a voltage of 1.2V configured by the
> bootloader, to the 1.1V set in the Device Tree.
> 
> According to the documentation, the VDDCORE supply should be between
> 0.99V and 1.21V; both values are therefore within the supported range.
> 
> However, VDDCORE being 1.1V results in the CI20 being very unstable,
> with corrupted memory, failures to boot, or reboots at random.

... and damaging the file system on SD card.

> The
> reason might be succint drops of the voltage below the minimum required.

1. with your patches (except this one) on top of upstream v6.4-rc7 and
ci20_defconfig I can still not boot with 1.100V.

2. but also not at 1.125V as by this patch.
[    0.647637] DCDC1: Bringing 1200000uV into 1125000-1125000uV

3. my board needs 1.150V as minimum, reporting:
[    0.647627] DCDC1: Bringing 1200000uV into 1150000-1150000uV

That is good news that it does not need 1.200V at the upper limit.

4. next, with this setup I can see the bluetooth chip (with default MAC
address 43:30:B1:00:00:00), but it is not useable (maybe my user space).

And there no WiFi. Rather, I have to disable the brcmfmac driver or
otherwise I can't even complete boot (hangs in a later stage) at all.

5. finally the mysterious result:

With all this merged with the letux-os kernel (and manually fixing minor
merge conflicts) and using letux_defconfig I can boot. Even with 1.100V
in the device tree, checked with /sys/kernel/debug):

root@letux:~# cat /sys/kernel/debug/regulator/regulator_summary 
 regulator                      use open bypass  opmode voltage current     min     max
---------------------------------------------------------------------------------------
 regulator-dummy                  3    2      0 unknown     0mV     0mA     0mV     0mV 
    13500000.usb-vusb_a           1                                 0mA     0mV     0mV
    13500000.usb-vusb_d           1                                 0mA     0mV     0mV
 eth0_power                       1    1      0 unknown  3300mV     0mA  3300mV  3300mV 
    16000000.dm9000-vcc           1                                 0mA     0mV     0mV
 otg_power                        1    2      0 unknown  5000mV     0mA  5000mV  5000mV 
    1000003c.usb-phy-vcc          1                                 0mA     0mV     0mV
    usb_phy-vcc                   0                                 0mA     0mV     0mV
 vcc_33v                          8    9      0 unknown  3300mV     0mA  3300mV  3300mV 
    13450000.mmc-vqmmc            1                                 0mA     0mV     0mV
    13450000.mmc-vmmc             1                                 0mA  3300mV  3400mV
    DCDC1                         1    0      0 standby  1100mV     0mA  1100mV  1100mV 
    DCDC2                         1    0      0 standby  1500mV     0mA  1500mV  1500mV 
    DCDC3                         1    0      0 unknown  3300mV     0mA  3300mV  3300mV 
    LDO5                          1    0      0 unknown  2500mV     0mA  2500mV  2500mV 
    LDO6                          1    1      0  normal  1800mV     0mA  1800mV  1800mV 
       13460000.mmc-vqmmc         1                                 0mA     0mV     0mV
    LDO7                          0    0      0 unknown  2800mV     0mA  2800mV  2800mV 
    LDO8                          0    0      0 unknown  1500mV     0mA  1500mV  1500mV 
 SUDCDC_REG4                      2    1      0  normal  5000mV     0mA  5000mV  5000mV 
    bt_power                      2    1      0 unknown  3300mV     0mA  3300mV  3300mV 
       wifi_power                 2    1      0 unknown  3300mV     0mA  3300mV  3300mV 
          13460000.mmc-vmmc       1                                 0mA  3300mV  3400mV
 LDO_REG9                         1    0      0 unknown  3300mV     0mA  3300mV  3300mV 
 LDO_REG10                        1    0      0 unknown  1200mV     0mA  1200mV  1200mV 
root@letux:~# uname -a
Linux letux 6.4.0-rc7-letux-ci20+ #13881 SMP PREEMPT Fri Jun 23 17:23:42 CEST 2023 mips GNU/Linux
root@letux:~# 

And I there have WiFi working fine.

But no Bluetooth interface at all (although driver is compiled).

A potential hint could be that DCDC1 is enabled a little later during boot than with ci20_defconfig:

[    1.077926] DCDC1: Bringing 1200000uV into 1100000-1100000uV
[    1.096997] DCDC1: 1100 mV, enabled

And another test with trying 1.000V hangs immediately after this:

[    1.032846] DCDC1: Bringing 1200000uV into 1000000-1000000uV

Maybe it is a too big step during operation.

For the records:

- I just swapped the clean compiled uImage, kernel modules and ci20.dtb
  between all these tests (and fsck the SD card before).

- we have some experimental SMP patches by Yanjie Zhou (and other nice
  stuff not pushed upstream) in the Letux kernel so that any of thes
  may have an influence.

So I'd say let's postpone this 1.125V patch until your other patches
arrive upstream. Then I will rebase our Letux kernel anyways and then
I can analyse a little easier what makes all these differences (because
then no merge and manual conflict resolution is involved any more and
there are better chances for a bisect to be helpful).

Best regards,
Nikolaus


> 
> Raising the minimum voltage to 1.125 volts seems to be enough to address
> this issue, while still keeping a relatively low core voltage which
> helps for power consumption and thermals.
> 
> Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node names")
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> 
> ---
> Cc: H. Nikolaus Schaller <hns@goldelico.com>
> ---
> arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/boot/dts/ingenic/ci20.dts b/arch/mips/boot/dts/ingenic/ci20.dts
> index cec0caa2350c..a141a699b790 100644
> --- a/arch/mips/boot/dts/ingenic/ci20.dts
> +++ b/arch/mips/boot/dts/ingenic/ci20.dts
> @@ -298,8 +298,8 @@ act8600: act8600@5a {
> 
> 		regulators {
> 			vddcore: DCDC1 {
> -				regulator-min-microvolt = <1100000>;
> -				regulator-max-microvolt = <1100000>;
> +				regulator-min-microvolt = <1125000>;
> +				regulator-max-microvolt = <1125000>;
> 				vp1-supply = <&vcc_33v>;
> 				regulator-always-on;
> 			};
> -- 
> 2.40.1
> 

Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[Paul Cercueil]

Hi Nikolaus,

Le vendredi 23 juin 2023 à 18:13 +0200, H. Nikolaus Schaller a écrit :
> Hi Paul, Thomas,
> here are my test results.
> 
> > Am 22.06.2023 um 19:59 schrieb Paul Cercueil
> > <paul@crapouillou.net>:
> > 
> > Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
> > names") caused the VDDCORE power supply (regulated by the ACT8600's
> > DCDC1 output) to drop from a voltage of 1.2V configured by the
> > bootloader, to the 1.1V set in the Device Tree.
> > 
> > According to the documentation, the VDDCORE supply should be
> > between
> > 0.99V and 1.21V; both values are therefore within the supported
> > range.
> > 
> > However, VDDCORE being 1.1V results in the CI20 being very
> > unstable,
> > with corrupted memory, failures to boot, or reboots at random.
> 
> ... and damaging the file system on SD card.
> 
> > The
> > reason might be succint drops of the voltage below the minimum
> > required.
> 
> 1. with your patches (except this one) on top of upstream v6.4-rc7
> and
> ci20_defconfig I can still not boot with 1.100V.
> 
> 2. but also not at 1.125V as by this patch.
> [    0.647637] DCDC1: Bringing 1200000uV into 1125000-1125000uV
> 
> 3. my board needs 1.150V as minimum, reporting:
> [    0.647627] DCDC1: Bringing 1200000uV into 1150000-1150000uV

Heh. I was fearing this would be the case.

> 
> That is good news that it does not need 1.200V at the upper limit.
> 
> 4. next, with this setup I can see the bluetooth chip (with default
> MAC
> address 43:30:B1:00:00:00), but it is not useable (maybe my user
> space).
> 
> And there no WiFi. Rather, I have to disable the brcmfmac driver or
> otherwise I can't even complete boot (hangs in a later stage) at all.

Most likely it's because of an invalid firmware file. It happened to me
with every single firmware file (including the one in the linux-
firmware repository at that time) except the one found on the CI20's
Debian image.

Since then Broadcom guys updated the firmware in linux-firmware to the
newest one they had, which works fine.

> 5. finally the mysterious result:
> 
> With all this merged with the letux-os kernel (and manually fixing
> minor
> merge conflicts) and using letux_defconfig I can boot. Even with
> 1.100V
> in the device tree, checked with /sys/kernel/debug):
> 
> root@letux:~# cat /sys/kernel/debug/regulator/regulator_summary 
>  regulator                      use open bypass  opmode voltage
> current     min     max
> ---------------------------------------------------------------------
> ------------------
>  regulator-dummy                  3    2      0 unknown     0mV    
> 0mA     0mV     0mV 
>     13500000.usb-vusb_a           1                                
> 0mA     0mV     0mV
>     13500000.usb-vusb_d           1                                
> 0mA     0mV     0mV
>  eth0_power                       1    1      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>     16000000.dm9000-vcc           1                                
> 0mA     0mV     0mV
>  otg_power                        1    2      0 unknown  5000mV    
> 0mA  5000mV  5000mV 
>     1000003c.usb-phy-vcc          1                                
> 0mA     0mV     0mV
>     usb_phy-vcc                   0                                
> 0mA     0mV     0mV
>  vcc_33v                          8    9      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>     13450000.mmc-vqmmc            1                                
> 0mA     0mV     0mV
>     13450000.mmc-vmmc             1                                
> 0mA  3300mV  3400mV
>     DCDC1                         1    0      0 standby  1100mV    
> 0mA  1100mV  1100mV 
>     DCDC2                         1    0      0 standby  1500mV    
> 0mA  1500mV  1500mV 
>     DCDC3                         1    0      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>     LDO5                          1    0      0 unknown  2500mV    
> 0mA  2500mV  2500mV 
>     LDO6                          1    1      0  normal  1800mV    
> 0mA  1800mV  1800mV 
>        13460000.mmc-vqmmc         1                                
> 0mA     0mV     0mV
>     LDO7                          0    0      0 unknown  2800mV    
> 0mA  2800mV  2800mV 
>     LDO8                          0    0      0 unknown  1500mV    
> 0mA  1500mV  1500mV 
>  SUDCDC_REG4                      2    1      0  normal  5000mV    
> 0mA  5000mV  5000mV 
>     bt_power                      2    1      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>        wifi_power                 2    1      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>           13460000.mmc-vmmc       1                                
> 0mA  3300mV  3400mV
>  LDO_REG9                         1    0      0 unknown  3300mV    
> 0mA  3300mV  3300mV 
>  LDO_REG10                        1    0      0 unknown  1200mV    
> 0mA  1200mV  1200mV 
> root@letux:~# uname -a
> Linux letux 6.4.0-rc7-letux-ci20+ #13881 SMP PREEMPT Fri Jun 23
> 17:23:42 CEST 2023 mips GNU/Linux
> root@letux:~# 
> 
> And I there have WiFi working fine.
> 
> But no Bluetooth interface at all (although driver is compiled).
> 
> A potential hint could be that DCDC1 is enabled a little later during
> boot than with ci20_defconfig:
> 
> [    1.077926] DCDC1: Bringing 1200000uV into 1100000-1100000uV
> [    1.096997] DCDC1: 1100 mV, enabled
> 
> And another test with trying 1.000V hangs immediately after this:
> 
> [    1.032846] DCDC1: Bringing 1200000uV into 1000000-1000000uV
> 
> Maybe it is a too big step during operation.

1.0V is about as low as you can get with theorically perfect power
supply, I doubt that you can use this voltage in the real world.

It's strange that your letux kernel can set 1.1V and be stable, while
you need 1.15V with the upstream kernel. I wonder what could be the
cause.

> 
> For the records:
> 
> - I just swapped the clean compiled uImage, kernel modules and
> ci20.dtb
>   between all these tests (and fsck the SD card before).
> 
> - we have some experimental SMP patches by Yanjie Zhou (and other
> nice
>   stuff not pushed upstream) in the Letux kernel so that any of thes
>   may have an influence.
> 
> So I'd say let's postpone this 1.125V patch until your other patches
> arrive upstream. Then I will rebase our Letux kernel anyways and then
> I can analyse a little easier what makes all these differences
> (because
> then no merge and manual conflict resolution is involved any more and
> there are better chances for a bisect to be helpful).

Thomas already merged it, so I guess we have 1.125V now.

Which is better than nothing; instead of not working on both our
boards, at least now v6.4 will work on one of them ;)

Note that I was testing my patches on top of the vanilla kernel,
without any local patches.

> 
> Best regards,
> Nikolaus

Cheers,
-Paul
> 

> > Raising the minimum voltage to 1.125 volts seems to be enough to
> > address
> > this issue, while still keeping a relatively low core voltage which
> > helps for power consumption and thermals.
> > 
> > Fixes: 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
> > names")
> > Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> > 
> > ---
> > Cc: H. Nikolaus Schaller <hns@goldelico.com>
> > ---
> > arch/mips/boot/dts/ingenic/ci20.dts | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/mips/boot/dts/ingenic/ci20.dts
> > b/arch/mips/boot/dts/ingenic/ci20.dts
> > index cec0caa2350c..a141a699b790 100644
> > --- a/arch/mips/boot/dts/ingenic/ci20.dts
> > +++ b/arch/mips/boot/dts/ingenic/ci20.dts
> > @@ -298,8 +298,8 @@ act8600: act8600@5a {
> > 
> >                 regulators {
> >                         vddcore: DCDC1 {
> > -                               regulator-min-microvolt =
> > <1100000>;
> > -                               regulator-max-microvolt =
> > <1100000>;
> > +                               regulator-min-microvolt =
> > <1125000>;
> > +                               regulator-max-microvolt =
> > <1125000>;
> >                                 vp1-supply = <&vcc_33v>;
> >                                 regulator-always-on;
> >                         };
> > -- 
> > 2.40.1
> > 
> 

Re: [PATCH] MIPS: DTS: CI20: Raise VDDCORE voltage to 1.125 volts

[H. Nikolaus Schaller]

Hi Paul,

> Am 23.06.2023 um 18:31 schrieb Paul Cercueil <paul@crapouillou.net>:
> 
> Hi Nikolaus,
> 
> Le vendredi 23 juin 2023 à 18:13 +0200, H. Nikolaus Schaller a écrit :
>> Hi Paul, Thomas,
>> here are my test results.
>> 
>>> Am 22.06.2023 um 19:59 schrieb Paul Cercueil
>>> <paul@crapouillou.net>:
>>> 
>>> Commit 08384e80a70f ("MIPS: DTS: CI20: Fix ACT8600 regulator node
>>> names") caused the VDDCORE power supply (regulated by the ACT8600's
>>> DCDC1 output) to drop from a voltage of 1.2V configured by the
>>> bootloader, to the 1.1V set in the Device Tree.
>>> 
>>> According to the documentation, the VDDCORE supply should be
>>> between
>>> 0.99V and 1.21V; both values are therefore within the supported
>>> range.
>>> 
>>> However, VDDCORE being 1.1V results in the CI20 being very
>>> unstable,
>>> with corrupted memory, failures to boot, or reboots at random.
>> 
>> ... and damaging the file system on SD card.
>> 
>>> The
>>> reason might be succint drops of the voltage below the minimum
>>> required.
>> 
>> 1. with your patches (except this one) on top of upstream v6.4-rc7
>> and
>> ci20_defconfig I can still not boot with 1.100V.
>> 
>> 2. but also not at 1.125V as by this patch.
>> [    0.647637] DCDC1: Bringing 1200000uV into 1125000-1125000uV
>> 
>> 3. my board needs 1.150V as minimum, reporting:
>> [    0.647627] DCDC1: Bringing 1200000uV into 1150000-1150000uV
> 
> Heh. I was fearing this would be the case.
> 
>> 
>> That is good news that it does not need 1.200V at the upper limit.
>> 
>> 4. next, with this setup I can see the bluetooth chip (with default
>> MAC
>> address 43:30:B1:00:00:00), but it is not useable (maybe my user
>> space).
>> 
>> And there no WiFi. Rather, I have to disable the brcmfmac driver or
>> otherwise I can't even complete boot (hangs in a later stage) at all.
> 
> Most likely it's because of an invalid firmware file. It happened to me
> with every single firmware file (including the one in the linux-
> firmware repository at that time) except the one found on the CI20's
> Debian image.
> 
> Since then Broadcom guys updated the firmware in linux-firmware to the
> newest one they had, which works fine.

Well, I have used exactly the same /lib/firmware directory in both cases.
Even the same SD card... Nothing removed, replaced or changed with the
firmware file.

I.e. I have just swapped kernel, dtb and modules on the same SD card.

So the difference is inside one of these, not the firmware but I have not
yet searched for the detail...

> 
>> 5. finally the mysterious result:
>> 
>> With all this merged with the letux-os kernel (and manually fixing
>> minor
>> merge conflicts) and using letux_defconfig I can boot. Even with
>> 1.100V
>> in the device tree, checked with /sys/kernel/debug):
>> 
>> root@letux:~# cat /sys/kernel/debug/regulator/regulator_summary 
>>  regulator                      use open bypass  opmode voltage
>> current     min     max
>> ---------------------------------------------------------------------
>> ------------------
>>  regulator-dummy                  3    2      0 unknown     0mV    
>> 0mA     0mV     0mV 
>>     13500000.usb-vusb_a           1                                
>> 0mA     0mV     0mV
>>     13500000.usb-vusb_d           1                                
>> 0mA     0mV     0mV
>>  eth0_power                       1    1      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>     16000000.dm9000-vcc           1                                
>> 0mA     0mV     0mV
>>  otg_power                        1    2      0 unknown  5000mV    
>> 0mA  5000mV  5000mV 
>>     1000003c.usb-phy-vcc          1                                
>> 0mA     0mV     0mV
>>     usb_phy-vcc                   0                                
>> 0mA     0mV     0mV
>>  vcc_33v                          8    9      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>     13450000.mmc-vqmmc            1                                
>> 0mA     0mV     0mV
>>     13450000.mmc-vmmc             1                                
>> 0mA  3300mV  3400mV
>>     DCDC1                         1    0      0 standby  1100mV    
>> 0mA  1100mV  1100mV 
>>     DCDC2                         1    0      0 standby  1500mV    
>> 0mA  1500mV  1500mV 
>>     DCDC3                         1    0      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>     LDO5                          1    0      0 unknown  2500mV    
>> 0mA  2500mV  2500mV 
>>     LDO6                          1    1      0  normal  1800mV    
>> 0mA  1800mV  1800mV 
>>        13460000.mmc-vqmmc         1                                
>> 0mA     0mV     0mV
>>     LDO7                          0    0      0 unknown  2800mV    
>> 0mA  2800mV  2800mV 
>>     LDO8                          0    0      0 unknown  1500mV    
>> 0mA  1500mV  1500mV 
>>  SUDCDC_REG4                      2    1      0  normal  5000mV    
>> 0mA  5000mV  5000mV 
>>     bt_power                      2    1      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>        wifi_power                 2    1      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>           13460000.mmc-vmmc       1                                
>> 0mA  3300mV  3400mV
>>  LDO_REG9                         1    0      0 unknown  3300mV    
>> 0mA  3300mV  3300mV 
>>  LDO_REG10                        1    0      0 unknown  1200mV    
>> 0mA  1200mV  1200mV 
>> root@letux:~# uname -a
>> Linux letux 6.4.0-rc7-letux-ci20+ #13881 SMP PREEMPT Fri Jun 23
>> 17:23:42 CEST 2023 mips GNU/Linux
>> root@letux:~# 
>> 
>> And I there have WiFi working fine.
>> 
>> But no Bluetooth interface at all (although driver is compiled).
>> 
>> A potential hint could be that DCDC1 is enabled a little later during
>> boot than with ci20_defconfig:
>> 
>> [    1.077926] DCDC1: Bringing 1200000uV into 1100000-1100000uV
>> [    1.096997] DCDC1: 1100 mV, enabled
>> 
>> And another test with trying 1.000V hangs immediately after this:
>> 
>> [    1.032846] DCDC1: Bringing 1200000uV into 1000000-1000000uV
>> 
>> Maybe it is a too big step during operation.
> 
> 1.0V is about as low as you can get with theorically perfect power
> supply, I doubt that you can use this voltage in the real world.

Indeed. There may be some more mV drop. I haven't tried 1.050V (yet).

> 
> It's strange that your letux kernel can set 1.1V and be stable, while
> you need 1.15V with the upstream kernel. I wonder what could be the
> cause.

Yes, that is a mysterium...

> 
>> 
>> For the records:
>> 
>> - I just swapped the clean compiled uImage, kernel modules and
>> ci20.dtb
>>   between all these tests (and fsck the SD card before).
>> 
>> - we have some experimental SMP patches by Yanjie Zhou (and other
>> nice
>>   stuff not pushed upstream) in the Letux kernel so that any of thes
>>   may have an influence.
>> 
>> So I'd say let's postpone this 1.125V patch until your other patches
>> arrive upstream. Then I will rebase our Letux kernel anyways and then
>> I can analyse a little easier what makes all these differences
>> (because
>> then no merge and manual conflict resolution is involved any more and
>> there are better chances for a bisect to be helpful).
> 
> Thomas already merged it, so I guess we have 1.125V now.
> 
> Which is better than nothing; instead of not working on both our
> boards, at least now v6.4 will work on one of them ;)

And it will not break LetuxOS if rebased. That is what we need for further
analysis.

> 
> Note that I was testing my patches on top of the vanilla kernel,
> without any local patches.

I do the same but have a better result with adding my local patches.
So they must improve something even more (except than making Bluetooth worse)...
But I don't know what it is.

Something for future analysis.

BR and thanks for building a basis,
Nikolaus