On 3/18/23 22:20, Simon Glass wrote:
Hi Eugen,
On Thu, 16 Mar 2023 at 07:53, Eugen Hristev <eugen.hris...@collabora.com> wrote:
Some devices share a regulator supply, when the first one will request
regulator disable, the second device will have it's supply cut off before
graciously shutting down. Hence there will be timeouts and other failed
operations.
Implement a reference counter mechanism similar with what is done in
Linux, to keep track of enable and disable requests, and only disable the
regulator when the last of the consumers has requested shutdown.
Signed-off-by: Eugen Hristev <eugen.hris...@collabora.com>
---
drivers/power/regulator/regulator_common.c | 22 ++++++++++++++++++++++
drivers/power/regulator/regulator_common.h | 1 +
2 files changed, 23 insertions(+)
This seems reasonable to me. I mostly worry about visibility, since it
returns 0 in all cases so if you do actually want to shut it down, it
silently ignored you in some situations. I've made some suggestions
below.
diff --git a/drivers/power/regulator/regulator_common.c
b/drivers/power/regulator/regulator_common.c
index 93d8196b381e..edda25336176 100644
--- a/drivers/power/regulator/regulator_common.c
+++ b/drivers/power/regulator/regulator_common.c
@@ -73,6 +73,23 @@ int regulator_common_set_enable(const struct udevice *dev,
Please update the docs for this function in the header file.
Okay
return 0;
}
+ /* If previously enabled, increase count */
+ if (enable && dev_pdata->enable_count > 0) {
+ dev_pdata->enable_count++;
+ return 0;
Should we return -EALREADY ?
I think not. It's not an error, we should just increase count, the
caller should be told that there is no error happening.
+ }
+
+ if (!enable) {
+ if (dev_pdata->enable_count > 1) {
+ /* If enabled multiple times, decrease count */
+ dev_pdata->enable_count--;
Return -EBUSY ?
Same goes here. The disable was successful, hence no error, but the
regulator is not turned off , because someone else is still using it.
+ return 0;
+ } else if (!dev_pdata->enable_count) {
+ /* If already disabled, do nothing */
Is this case an error? Should we return -EPERM ?
Maybe here we could return an error, saying that it's already disabled,
but since it's a shared resource, this could tell the caller whether
someone else is using the resource, and I don't think we should leak
this information. It might be used in a way to find out information
about the state of the system which might be a security problem ?
I think that a shared resource usage should be transparent to the caller
, such that only the driver should manage it's power on/off and know who
is using it.
Do you agree ?
+ return 0;
+ }
+ }
+
ret = dm_gpio_set_value(&dev_pdata->gpio, enable);
if (ret) {
pr_err("Can't set regulator : %s gpio to: %d\n", dev->name,
@@ -87,5 +104,10 @@ int regulator_common_set_enable(const struct udevice *dev,
if (!enable && dev_pdata->off_on_delay_us)
udelay(dev_pdata->off_on_delay_us);
+ if (enable)
+ dev_pdata->enable_count++;
+ else
+ dev_pdata->enable_count--;
+
return 0;
}
diff --git a/drivers/power/regulator/regulator_common.h
b/drivers/power/regulator/regulator_common.h
index c10492f01675..8167bc866261 100644
--- a/drivers/power/regulator/regulator_common.h
+++ b/drivers/power/regulator/regulator_common.h
@@ -13,6 +13,7 @@ struct regulator_common_plat {
struct gpio_desc gpio; /* GPIO for regulator enable control */
unsigned int startup_delay_us;
unsigned int off_on_delay_us;
+ unsigned int enable_count;
};
int regulator_common_of_to_plat(struct udevice *dev,
--
2.34.1
Also I would appreciate a patch to rename dev_pdata to plat if you have time.
I will have a look
Regards,
Simon
