Hi Baruch,
On mer., déc. 13 2017, Baruch Siach <baruch@xxxxxxxxxx> wrote:
> Hi Gregory,
>
> On Mon, Dec 11, 2017 at 06:02:49PM +0100, Gregory CLEMENT wrote:
>> On lun., déc. 11 2017, Baruch Siach <baruch@xxxxxxxxxx> wrote:
>> > On Mon, Dec 11, 2017 at 04:09:32PM +0100, Miquel RAYNAL wrote:
>> >> On Sun, 3 Dec 2017 13:11:23 +0200
>> >> Baruch Siach <baruch@xxxxxxxxxx> wrote:
>> >>
>> >> > 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@xxxxxxxxxx>
>> >> > ---
>> >> > 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 :)
>>
>> > 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.
>
>> 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.
>>
>> > 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
>
> --
> http://baruch.siach.name/blog/ ~. .~ Tk Open Systems
> =}------------------------------------------------ooO--U--Ooo------------{=
> - baruch@xxxxxxxxxx - tel: +972.2.679.5364, http://www.tkos.co.il -
--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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