This patch series adds a variant of regulator_get() which allows regulator consumers to tell the core that the supply they are requesting may genuinely be absent in the system. The goal is to help address some of the problems with handling errors in regulator_get() in drivers that are newly converted to the regulator API by allowing the core to provide stub regulators for supplies that aren't hooked up without disrupting the operation of drivers like MMC drivers which may genuinely not have some of their supplies hooked up.
Currently the code simply introduces a new API call with exactly the same implementation as regulator_get() so there should be zero impact from the series other than a slightly larger kernel.
Right now all the MMC users are converted over as-is, though it does look like drivers such as sdhci really ought to be insisting on having a regulator for VMMC in the same way that the MMC core helper does (and indeed in that case it looks like it ought to be converted over to the core code).
If this series is OK I'd like to merge it via the regulator tree so that the functionality to make use of the optional regulators can be built out on top of it.
Mark Brown (5): regulator: core: Provide hints to the core about optional supplies mmc: core: Indicate that vmmcq may be absent mmc: sdhci: Indicate that regulators may be absent mmc: dw_mmc: Indicate that regulators may be absent mmc: pxamci: Indicate that regulators may be absent
drivers/mmc/core/core.c | 2 +- drivers/mmc/host/dw_mmc.c | 2 +- drivers/mmc/host/pxamci.c | 2 +- drivers/mmc/host/sdhci.c | 4 +-- drivers/regulator/core.c | 59 ++++++++++++++++++++++++++++++++++++++ include/linux/regulator/consumer.h | 18 +++++++++++- 6 files changed, 81 insertions(+), 6 deletions(-)
Hi,
On Tue, Jul 30 2013, Mark Brown wrote:
This patch series adds a variant of regulator_get() which allows regulator consumers to tell the core that the supply they are requesting may genuinely be absent in the system. The goal is to help address some of the problems with handling errors in regulator_get() in drivers that are newly converted to the regulator API by allowing the core to provide stub regulators for supplies that aren't hooked up without disrupting the operation of drivers like MMC drivers which may genuinely not have some of their supplies hooked up.
Currently the code simply introduces a new API call with exactly the same implementation as regulator_get() so there should be zero impact from the series other than a slightly larger kernel.
Looks good:
Acked-by: Chris Ball cjb@laptop.org
Right now all the MMC users are converted over as-is, though it does look like drivers such as sdhci really ought to be insisting on having a regulator for VMMC in the same way that the MMC core helper does (and indeed in that case it looks like it ought to be converted over to the core code).
I didn't follow this part -- I don't think the MMC core insists on a VMMC regulator, and I don't think sdhci should either, because e.g. an x86 laptop isn't going to have one. What am I missing?
Thanks,
- Chris.
On Tue, Jul 30, 2013 at 01:40:28PM +0100, Chris Ball wrote:
On Tue, Jul 30 2013, Mark Brown wrote:
Right now all the MMC users are converted over as-is, though it does look like drivers such as sdhci really ought to be insisting on having a regulator for VMMC in the same way that the MMC core helper does (and indeed in that case it looks like it ought to be converted over to the core code).
I didn't follow this part -- I don't think the MMC core insists on a VMMC regulator, and I don't think sdhci should either, because e.g. an x86 laptop isn't going to have one. What am I missing?
You're missing the fact that there will be a VMMC regulator there since the card needs power to function, it just might not be one that software knows about or can control. If it's one that software can control that's not mapped in properly (eg, because the driver for the regulator wasn't loaded) then obviously that's a serious problem and power saving features in the regulator API may for example turn off the supply even if it's on by default since they can't tell it's in use.
As things stand the expectation for x86 type systems is that MMC controllers attached via PCI or USB ought to be setting up a fixed regulator so that the consumer part can proceed without ignoring errors that might be serious on other systems. It's probably not a bad idea to do this anyway though hopefully in the future this work will make it less needed. For embedded systems the system integration ought to be doing the same thing, normally as part of the configuration of the PMIC.
The goal of this series is to make it much easier for the regulator core to transparently support such systems where the regulators aren't visible to software by transparently stubbing out normal supplies that really must be present somehow for the hardware to operate without confusing things by also stubbing out suppies that may be missing in normal operation. This is the problem for the existing stubbing support - it works well for normal supplies but it means that any consumer that wants to handle a supply that's not there can't tell it's missing.
linaro-kernel@lists.linaro.org
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Chris Ball -
Mark Brown