Hi,
Apologies for the delayed reply.
On 12/09/2013 11:38 AM, Mark Rutland wrote:
On Fri, Dec 06, 2013 at 11:59:46AM +0000, Georgi Djakov wrote:
On 12/05/2013 11:52 AM, Mark Rutland wrote:
[...]
+
+- qcom,{vdd,vdd-io}-lpm-sup - specifies whether the supply can be kept in low power mode.
Boolean? Please specify types on properties.
Yes, it is boolean. I'll note it in the documentation. Thanks!
Can you elaborate on what this means? When can a supply not be kept in
low power mode?
The vdd-io for example is a regulator that is always-on and may be
shared with multiple other peripherals as well. It should not be
disabled by the driver, but instead put in low power mode when unused.
The fact that the regulator is driving other peripherals doesn't seem
like a property of the SDHCI to me. What are these other peripherals?
Agree! I'll drop this property.
When you say should not be disabled by the driver, do you mean that
another peripheral's driver shouldn't be able to disable the regulator
feeding the SDHCI, or the SDHCI driver shouldn't be able to disable a
regulator in use by another peripheral?
The regulator will not be disabled in any case as it will be marked as
always-on.
When in low power mode, is the SDHCI functional?
+- qcom,{vdd,vdd-io}-voltage-level - specifies voltage levels for the supply.
+ Should be specified in pairs (min, max), units uV.
+- qcom,{vdd,vdd-io}-current-level - specifies load levels for the supply in lpm
+ or high power mode (hpm). Should be specified in pairs (lpm, hpm), units uA.
Can you not query these from the regulator framework?
If these are configuration, why are they necessary?
As some regulators are shared and can have multiple consumers, these
properties can be used for voltage and load current aggregation.
The voltage-level is the "supported voltage" by the controller, that
also (at least on my platform) matches the corresponding regulator
voltage. I probably can drop the voltage-level property and get voltage
via the regulator framework helper functions, but the load current
values are different for each sdhc.
From the very limited documentation that i have, i think this is
describing the hardware configuration and should be in the device-tree.
If these are the voltages / currents supported by the SDHCI, then that
seems like it makes sense to have in DT, if they're likely to be
variable in practice. How variable do you expect these to be?
The voltages vary depending on the function. For example the vdd-io for
eMMC is 1.2 - 1.8v, for SD cards 1.8 - 2.95v and for SDIO 1.8v.
So, one way is using -min/-max suffixes and the other can be introducing
a for ex. "function" property (emmc/card/sdio) and moving the voltage
range definitions into the driver.
Also, I'd recommend splitting them in to separate -min and -max
properties, it makes it far clearer what they're actually for.
Thanks,
Georgi
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