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[PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.

Started byEric Anholt <eric@anholt.net>
First post2016-02-26 21:50 +0100
Last post2016-03-03 23:40 +0100
Articles 4 — 2 participants

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  [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups. Eric Anholt <eric@anholt.net> - 2016-02-26 21:50 +0100
    Re: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard  groups. Stephen Warren <swarren@wwwdotorg.org> - 2016-03-03 22:30 +0100
      Re: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups. Eric Anholt <eric@anholt.net> - 2016-03-03 23:40 +0100
        Re: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard  groups. Stephen Warren <swarren@wwwdotorg.org> - 2016-03-03 23:40 +0100

#1344666 — [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.

FromEric Anholt <eric@anholt.net>
Date2016-02-26 21:50 +0100
Subject[PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.
Message-ID<r6xuN-j0-7@gated-at.bofh.it>
Since all of these pins were documented, we can use their names to
explain what's going on.

Signed-off-by: Eric Anholt <eric@anholt.net>
---
 arch/arm/boot/dts/bcm2835-rpi-a-plus.dts | 17 ++++++++++-------
 arch/arm/boot/dts/bcm2835-rpi-a.dts      | 17 ++++++++++-------
 arch/arm/boot/dts/bcm2835-rpi-b-plus.dts | 17 ++++++++++-------
 arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts | 17 ++++++++++-------
 arch/arm/boot/dts/bcm2835-rpi-b.dts      | 10 +++++++++-
 arch/arm/boot/dts/bcm2835-rpi.dtsi       |  5 -----
 arch/arm/boot/dts/bcm2836-rpi-2-b.dts    | 17 ++++++++++-------
 7 files changed, 59 insertions(+), 41 deletions(-)

diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
index 228614f..0a8b92e 100644
--- a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
+++ b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
@@ -21,11 +21,14 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &i2s_alt0 &alt3>;
-
-	/* I2S interface */
-	i2s_alt0: i2s_alt0 {
-		brcm,pins = <18 19 20 21>;
-		brcm,function = <BCM2835_FSEL_ALT0>;
-	};
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pcm_gpio18
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
diff --git a/arch/arm/boot/dts/bcm2835-rpi-a.dts b/arch/arm/boot/dts/bcm2835-rpi-a.dts
index ddbbbbd..d093407 100644
--- a/arch/arm/boot/dts/bcm2835-rpi-a.dts
+++ b/arch/arm/boot/dts/bcm2835-rpi-a.dts
@@ -14,11 +14,14 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &i2s_alt2 &alt3>;
-
-	/* I2S interface */
-	i2s_alt2: i2s_alt2 {
-		brcm,pins = <28 29 30 31>;
-		brcm,function = <BCM2835_FSEL_ALT2>;
-	};
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pcm_gpio28
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
diff --git a/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts
index ef54050..c26b81d 100644
--- a/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts
+++ b/arch/arm/boot/dts/bcm2835-rpi-b-plus.dts
@@ -21,11 +21,14 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &i2s_alt0 &alt3>;
-
-	/* I2S interface */
-	i2s_alt0: i2s_alt0 {
-		brcm,pins = <18 19 20 21>;
-		brcm,function = <BCM2835_FSEL_ALT0>;
-	};
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pcm_gpio18
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
diff --git a/arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts b/arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts
index 86f1f2f..a5b606e 100644
--- a/arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts
+++ b/arch/arm/boot/dts/bcm2835-rpi-b-rev2.dts
@@ -14,11 +14,14 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &i2s_alt2 &alt3>;
-
-	/* I2S interface */
-	i2s_alt2: i2s_alt2 {
-		brcm,pins = <28 29 30 31>;
-		brcm,function = <BCM2835_FSEL_ALT2>;
-	};
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pcm_gpio28
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
diff --git a/arch/arm/boot/dts/bcm2835-rpi-b.dts b/arch/arm/boot/dts/bcm2835-rpi-b.dts
index 4859e9d..97e3c2f 100644
--- a/arch/arm/boot/dts/bcm2835-rpi-b.dts
+++ b/arch/arm/boot/dts/bcm2835-rpi-b.dts
@@ -14,5 +14,13 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &alt3>;
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
diff --git a/arch/arm/boot/dts/bcm2835-rpi.dtsi b/arch/arm/boot/dts/bcm2835-rpi.dtsi
index 76bdbca..141b18c 100644
--- a/arch/arm/boot/dts/bcm2835-rpi.dtsi
+++ b/arch/arm/boot/dts/bcm2835-rpi.dtsi
@@ -37,11 +37,6 @@
 		brcm,function = <BCM2835_FSEL_GPIO_OUT>;
 	};
 
-	alt0: alt0 {
-		brcm,pins = <0 1 2 3 4 5 7 8 9 10 11 14 15 40 45>;
-		brcm,function = <BCM2835_FSEL_ALT0>;
-	};
-
 	alt3: alt3 {
 		brcm,pins = <48 49 50 51 52 53>;
 		brcm,function = <BCM2835_FSEL_ALT3>;
diff --git a/arch/arm/boot/dts/bcm2836-rpi-2-b.dts b/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
index ff94666..52798ca 100644
--- a/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
+++ b/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
@@ -25,11 +25,14 @@
 };
 
 &gpio {
-	pinctrl-0 = <&gpioout &alt0 &i2s_alt0 &alt3>;
-
-	/* I2S interface */
-	i2s_alt0: i2s_alt0 {
-		brcm,pins = <18 19 20 21>;
-		brcm,function = <BCM2835_FSEL_ALT0>;
-	};
+	pinctrl-0 = <&i2c0_gpio0
+		     &i2c1_gpio2
+		     &gpclk0_gpio4
+		     &gpclk1_gpio5
+		     &spi0_gpio7
+		     &pcm_gpio18
+		     &pwm0_gpio40
+		     &pwm1_gpio45
+		     &gpioout
+		     &alt3>;
 };
-- 
2.7.0

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#1349595 — Re: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.

FromStephen Warren <swarren@wwwdotorg.org>
Date2016-03-03 22:30 +0100
SubjectRe: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.
Message-ID<r8IYO-4Fu-25@gated-at.bofh.it>
In reply to#1344666
On 02/26/2016 11:19 AM, Eric Anholt wrote:
> Since all of these pins were documented, we can use their names to
> explain what's going on.

> diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts

>   &gpio {
> +	pinctrl-0 = <&i2c0_gpio0
> +		     &i2c1_gpio2
> +		     &gpclk0_gpio4
> +		     &gpclk1_gpio5
> +		     &spi0_gpio7
> +		     &pcm_gpio18
> +		     &pwm0_gpio40
> +		     &pwm1_gpio45
> +		     &gpioout
> +		     &alt3>;
>   };

Why not convert alt3 to the new scheme too?

I think this configures too many pins, which in turn makes assumptions 
about what those pins are used for that may not be valid.

Recent RPi firmware configures almost all expansion connector GPIOs as 
GPIO-in. This ensures that no matter what is connected to the expansion 
connector, there can be no signal conflicts due to both the bcm283x and 
some external device both attempting to drive the same pin. I believe 
the default Linux pinmux should adopt the same approach, by simply not 
configuring any expansion connector pins except those known to have a 
100% hard-coded usage. For example, the HAT I2C pins must only be used 
for that purpose on the RPi, so even if the HW supported using them as 
arbitrary GPIO or PWM or ..., we know they're actually I2C.

So, I think this list should only include configuration for pins 
connected to on-board devices, or expansion pins that have a 100% known 
purpose.

(I can't quite remember how many pins are being configured in the 
upstream kernel's DT files at present; it's possible the complying with 
this rule may involve removing some pinctrl settings that are currently 
present to avoid conflicts. User-specific additions should come from DT 
overlays or manual DT edits.)

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#1349648

FromEric Anholt <eric@anholt.net>
Date2016-03-03 23:40 +0100
Message-ID<r8K4y-5Af-17@gated-at.bofh.it>
In reply to#1349595

[Multipart message — attachments visible in raw view] — view raw

Stephen Warren <swarren@wwwdotorg.org> writes:

> On 02/26/2016 11:19 AM, Eric Anholt wrote:
>> Since all of these pins were documented, we can use their names to
>> explain what's going on.
>
>> diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
>
>>   &gpio {
>> +	pinctrl-0 = <&i2c0_gpio0
>> +		     &i2c1_gpio2
>> +		     &gpclk0_gpio4
>> +		     &gpclk1_gpio5
>> +		     &spi0_gpio7
>> +		     &pcm_gpio18
>> +		     &pwm0_gpio40
>> +		     &pwm1_gpio45
>> +		     &gpioout
>> +		     &alt3>;
>>   };
>
> Why not convert alt3 to the new scheme too?

(covered in the next patch)

> I think this configures too many pins, which in turn makes assumptions 
> about what those pins are used for that may not be valid.
>
> Recent RPi firmware configures almost all expansion connector GPIOs as 
> GPIO-in. This ensures that no matter what is connected to the expansion 
> connector, there can be no signal conflicts due to both the bcm283x and 
> some external device both attempting to drive the same pin. I believe 
> the default Linux pinmux should adopt the same approach, by simply not 
> configuring any expansion connector pins except those known to have a 
> 100% hard-coded usage. For example, the HAT I2C pins must only be used 
> for that purpose on the RPi, so even if the HW supported using them as 
> arbitrary GPIO or PWM or ..., we know they're actually I2C.
>
> So, I think this list should only include configuration for pins 
> connected to on-board devices, or expansion pins that have a 100% known 
> purpose.
>
> (I can't quite remember how many pins are being configured in the 
> upstream kernel's DT files at present; it's possible the complying with 
> this rule may involve removing some pinctrl settings that are currently 
> present to avoid conflicts. User-specific additions should come from DT 
> overlays or manual DT edits.)

If we want to improve on our default pin configurations, I'm into that,
but I think the first step is to get groups split up so it's clear what
we're doing with pins in the first place.  This patch is just a no-op
change to get the board files to use smaller groups for
enabling/disabling, and we should stack functional changes after that.

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#1349654 — Re: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.

FromStephen Warren <swarren@wwwdotorg.org>
Date2016-03-03 23:40 +0100
SubjectRe: [PATCH 2/5] ARM: bcm2835: Replace alt0/i2s_alt[02] with standard groups.
Message-ID<r8K4z-5Af-37@gated-at.bofh.it>
In reply to#1349648
On 03/03/2016 03:28 PM, Eric Anholt wrote:
> Stephen Warren <swarren@wwwdotorg.org> writes:
>
>> On 02/26/2016 11:19 AM, Eric Anholt wrote:
>>> Since all of these pins were documented, we can use their names to
>>> explain what's going on.
>>
>>> diff --git a/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts b/arch/arm/boot/dts/bcm2835-rpi-a-plus.dts
>>
>>>    &gpio {
>>> +	pinctrl-0 = <&i2c0_gpio0
>>> +		     &i2c1_gpio2
>>> +		     &gpclk0_gpio4
>>> +		     &gpclk1_gpio5
>>> +		     &spi0_gpio7
>>> +		     &pcm_gpio18
>>> +		     &pwm0_gpio40
>>> +		     &pwm1_gpio45
>>> +		     &gpioout
>>> +		     &alt3>;
>>>    };
>>
>> Why not convert alt3 to the new scheme too?
>
> (covered in the next patch)
>
>> I think this configures too many pins, which in turn makes assumptions
>> about what those pins are used for that may not be valid.
>>
>> Recent RPi firmware configures almost all expansion connector GPIOs as
>> GPIO-in. This ensures that no matter what is connected to the expansion
>> connector, there can be no signal conflicts due to both the bcm283x and
>> some external device both attempting to drive the same pin. I believe
>> the default Linux pinmux should adopt the same approach, by simply not
>> configuring any expansion connector pins except those known to have a
>> 100% hard-coded usage. For example, the HAT I2C pins must only be used
>> for that purpose on the RPi, so even if the HW supported using them as
>> arbitrary GPIO or PWM or ..., we know they're actually I2C.
>>
>> So, I think this list should only include configuration for pins
>> connected to on-board devices, or expansion pins that have a 100% known
>> purpose.
>>
>> (I can't quite remember how many pins are being configured in the
>> upstream kernel's DT files at present; it's possible the complying with
>> this rule may involve removing some pinctrl settings that are currently
>> present to avoid conflicts. User-specific additions should come from DT
>> overlays or manual DT edits.)
>
> If we want to improve on our default pin configurations, I'm into that,
> but I think the first step is to get groups split up so it's clear what
> we're doing with pins in the first place.  This patch is just a no-op
> change to get the board files to use smaller groups for
> enabling/disabling, and we should stack functional changes after that.

I don't think it's worth making patches that change things around when 
they're immediately going to be thrown away. It is needless churn. If 
you take the approach of removing settings that shouldn't be applied, 
you'll vastly reduce (and possibly even completely eliminate) the work 
to more optimally represent what's left.

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