[PATCH v2 3/4] thermal: armada: add support for CP110

Hi Baruch,
 
 On mer., d?c. 13 2017, Baruch Siach [off-list ref] wrote:

Hi Gregory,

On Mon, Dec 11, 2017 at 06:02:49PM +0100, Gregory CLEMENT wrote:

quoted

 On lun., d?c. 11 2017, Baruch Siach [off-list ref] wrote:

quoted

On Mon, Dec 11, 2017 at 04:09:32PM +0100, Miquel RAYNAL wrote:

quoted

On Sun,  3 Dec 2017 13:11:23 +0200
Baruch Siach [off-list ref] wrote:

quoted

The CP110 component is integrated in the Armada 8k and 7k lines of
processors.

This patch also adds an option of offset to the MSB of the control
register. The existing DT binding for Armada 38x refers to a single
32 bit control register. It turns out that this is actually only the
MSB of the control area. Changing the binding to fix that would break
existing DT files, so the Armada 38x binding is left as is.

The new CP110 binding increases the size of the control area to 64
bits, thus moving the MSB to offset 4.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
v2: No change
---
 drivers/thermal/armada_thermal.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/armada_thermal.c

b/drivers/thermal/armada_thermal.c index 0eb82097571f..59b75f63945d
100644 --- a/drivers/thermal/armada_thermal.c

+++ b/drivers/thermal/armada_thermal.c

@@ -73,6 +73,7 @@ struct armada_thermal_data {
 	unsigned int temp_shift;
 	unsigned int temp_mask;
 	unsigned int is_valid_shift;
+	unsigned int control_msb_offset;
 };
 
 static void armadaxp_init_sensor(struct platform_device *pdev,

@@ -142,12 +143,14 @@ static void armada375_init_sensor(struct

platform_device *pdev, static void armada380_init_sensor(struct
platform_device *pdev, struct armada_thermal_priv *priv)
 {
-	unsigned long reg = readl_relaxed(priv->control);
+	void __iomem *control_msb =
+		priv->control + priv->data->control_msb_offset;
+	unsigned long reg = readl_relaxed(control_msb);
 
 	/* Reset hardware once */
 	if (!(reg & A380_HW_RESET)) {
 		reg |= A380_HW_RESET;
-		writel(reg, priv->control);
+		writel(reg, control_msb);
 		mdelay(10);
 	}
 }

@@ -266,6 +269,19 @@ static const struct armada_thermal_data

armada_ap806_data = { .signed_sample = true,
 };
 
+static const struct armada_thermal_data armada_cp110_data = {
+	.is_valid = armada_is_valid,
+	.init_sensor = armada380_init_sensor,

I see the initialization for CP110 thermal IP is close to
Armada-380's, but, as you point it in the commit log it is still
different.

I don't know what is the best way to handle this but until now each
new compatible had his own ->init_sensor function, shouldn't we do
the same here as changes are requested? This would naturally avoid the
situation with Armada-380 bindings.

I'm not sure I understand your suggestion.

There is no difference between the CP110 and the Armada 38x, as far as I can 
see. The only quirk is that the existing Armada 38x DT binding is wrong I that 
the 'reg' property references the control MSB, while leaving the LSB
out. We

Well I would not say it was wrong but more incomplete :)

quoted

can't change the Armada 38x binding without breaking existing DTs. The 
'control_msb_offset' field that this patch adds allows correct binding for 
CP110, while keeping compatibility with the existing Armada 38x
binding.

I am not against adding a new compatible string for CP110 but ot be
honest the new binding for CP110 does not bring anything as you don't
use at all the LSB register.

We don't use the LSB yet in mainline driver. But the vendor kernel uses it to 
"change temperature band gap circuit curve" (quoting vendor kernel commit 
4ff2d8a7d3 log). Chances are that we want to do this as well. But said commit 
changed the DT binding in an incompatible way. We can't do that, and we both 
agree on that.

quoted

Actually, if on Armada 375 we initially mapped the LSB register it was
to support an very early release of the SoC (stepping Z) and only for
resetting its value. So I guess you started to write the AP860 part
based on the Armada 375 and then found that we could map a more complete
range of the registers.

quoted

How would a separate init_sensor routine improve things?

So yes please do it, thanks to this you won't have to add the
control_msb_offset member and can use a clean function. Moreover if in
the future we see some usefulness for this LSB register then we could use
the new compatible for the Armada 38x.

There are two separate issues here:

  1. DT binding

  2. init_sensor callback implementation

We both agree on #1. The A38x and CP110 need separate compatible strings. In 
case we want to access the LSB control register on Armada 38x, we will need 
yet another compatible string (marvell,armada380-v2-thermal maybe?).

Actually, if it is _compatible_ then we will use the same compatible, ie
"marvell,armadacp110-thermal"

As for #2, I'm all for sharing as much code as possible. I find the vendor 
kernel approach of duplicating the init routines[1] unhelpful as it violates 
the DRY principle. The differences between armada380_init_sensor() and 
cp110_init_sensor() are minor. In my opinion, these differences should be 
expressed explicitly in the armada_thermal_data, in a similar way to my 
suggested control_msb_offset field. The vendor code hides these differences in 
slight variations of duplicated code.

What is the advantage of a separate init routine?

The main advantage is to be able keep the armada380_init_sensor as the
legacy init, and then being able to use the new armadacp110_init_sensor
for the new binding.

Gregory

baruch

[1] https://github.com/MarvellEmbeddedProcessors/linux-marvell/blob/linux-4.4.52-armada-17.10/drivers/thermal/armada_thermal.c

-- 
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-- 
Gregory Clement, Free Electrons
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