On Thu, Aug 21, 2014 at 09:38:29AM -0600, Stephen Warren wrote: > On 08/21/2014 12:58 AM, Thierry Reding wrote: > >On Wed, Aug 20, 2014 at 02:16:49PM -0600, Stephen Warren wrote: > >>On 08/13/2014 06:41 AM, Mikko Perttunen wrote: > >>>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. > >> > >>>diff --git a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt b/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt > >> > >>>+Hardware-triggered thermal reset: > >>>+On Tegra30, Tegra114 and Tegra124, if the 'i2c-thermtrip' subnode exists, > >>>+hardware-triggered thermal reset will be enabled. > >> > >>"will be enabled" sounds like SW behaviour, whereas DT is suppose to > >>describe HW, and leave SW to define its own behaviour. I would suggest: > >> > >>Optional sub-nodes: > >>i2c-thermtrip: Describes how to power off the system in the event of a > >> thermal emergency. > >> > >>>+Required properties for hardware-triggered thermal reset (inside 'i2c-thermtrip'): > >> > >>Simpler might be: > >> > >>Required properties for i2c-thermtrip node: > >> > >>>+- nvidia,pmu : Phandle to power management unit / PMIC handling poweroff > >>>+- nvidia,reg-addr : I2C register address to write poweroff command to > >>>+- nvidia,reg-data : Poweroff command to write to PMU > >> > >>Why are both the PMU/PMIC phandle and the register address/data required? I > >>thought the purpose of having the phandle was to allow the register address > >>and data to be queried from the PMU/PMIC driver. > >> > >>To me, it seems much simpler to get rid of the phandle and just hard-code > >>the I2C bus number, address, and data into this node, rather than having to > >>go query it from the PMU/PMIC driver, then find the I2C controller, then > >>query it for its ID (and hope that all HW modules that talk to I2C > >>controllers directly use the same numbering scheme...) > > > >I originally requested this to be changed. It seems wrong to duplicate > >information about the PMIC in both the PMIC device tree node and the > >i2c-thermtrip node if we can get the same information from the driver > >directly (via the phandle). It certainly requires a little more code, > >but at the advantage of not having to figure out the I2C controller > >hardware number and I2C slave addresses when writing the i2c-thermtrip > >node. > > I cant see that argument, but surely the PMIC driver can also supply the > "reg-addr" and "reg-data" values too, if it's already being queried for the > I2C device address and bus number? The binding above appears to duplicate > part of the information, while requiring querying of the other part. I suppose that could be done. It would take a new function to do that, though, since I'm not aware of a generic mechanism to query this kind of information from a PMIC (there's no generic PMIC API, either, so perhaps it would be a good time to create one?). The I2C controller and I2C slave are generic I2C properties, whereas the register and data to power off the device are very device specific. Thierry
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