On 11/12/2014 02:29 PM, Thierry Reding wrote:
On Wed, Nov 12, 2014 at 02:07:51PM +0200, Mikko Perttunen wrote:
On 11/11/2014 08:37 AM, Alexandre Courbot wrote:
On 11/10/2014 10:12 PM, Mikko Perttunen wrote:
From: Mikko Perttunen <mperttunen@xxxxxxxxxx>
Hardware-triggered thermal reset requires configuring the I2C
reset procedure. This configuration is read from the device tree,
so document the relevant properties in the binding documentation.
Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
Reviewed-by: Wei Ni <wni@xxxxxxxxxx>
Tested-by: Wei Ni <wni@xxxxxxxxxx>
---
.../bindings/arm/tegra/nvidia,tegra20-pmc.txt | 24
++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git
a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
index 68ac65f..dc13fb0 100644
--- a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
+++ b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt
@@ -47,6 +47,21 @@ Required properties when nvidia,suspend-mode=<0>:
sleep mode, the warm boot code will restore some PLLs, clocks and
then
bring up CPU0 for resuming the system.
+Hardware-triggered thermal reset:
+On Tegra30, Tegra114 and Tegra124, if the 'i2c-thermtrip' subnode
exists,
+hardware-triggered thermal reset will be enabled.
+
+Required properties for hardware-triggered thermal reset (inside
'i2c-thermtrip'):
+- nvidia,i2c-bus : Phandle to I2C bus containing the PMU
+- nvidia,bus-addr : Bus address of the PMU on the I2C bus
+- nvidia,reg-addr : I2C register address to write poweroff command to
+- nvidia,reg-data : Poweroff command to write to PMU
This binding is taking two different routes to provide values to the
driver:
1) It uses a phandle for i2c-bus (which must then be provided by another
binding implemented in the two following patches)
2) It uses direct values for bus-addr, reg-addr and reg-data.
Do we need to use both approaches? bus-addr could just as well be
obtained through a phandle to the i2c device and reading its reg
property. From this phandle you could also go back up to the bus, making
the i2c-bus property unnecessary. reg-addr and reg-data cannot be
specified that way, obviously.
This was in fact how I used to implement this, but Stephen or Thierry
pointed out that the reg property actually might not contain the correct
address (I think because the PMIC could have multiple addresses, and the one
in DT might not be the one that accepts the reset command).
The workaround for that was to either add this integer property for bus-addr
or add a new PMIC API for querying. I went for this as it is much simpler.
Actually I think I'd prefer to see i2c-bus become an integer property
instead of a phandle, because at the end of the day it is a value field
of a particular register and the reference is only used to retrieve that
value. It is not like we are actually going to call functions on the bus
instance or change its state. And for the single purpose of retrieving
that value, this binding requires the addition of a new property on the
bus node that will probably never be used for something else.
And this was how I used to implement this even earlier, but Thierry objected
to that since it was duplicating information :)
If I remember correctly what I was asking for was to derive as much as
possible from simply a phandle. That is, what I was after is a phandle
to the PMU and ideally a way for the PMU to pass back information about
the register and value for the power off command.
Given the lack of a PMU abstraction and how this is probably very Tegra
specific I was okay with leaving reg-addr and reg-data in the DT. But if
we can't derive even the slave address from a phandle along with the I2C
bus master, then I think there remains little point in doing it this way
at all.
If we're going to duplicate three properties, adding a fourth isn't
going to make it much worse.
Thierry
Yeah, I guess that's sensible. I'll change the phandle to an integer if
that's preferred.
Mikko
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