linux-kernel - [RFC PATCH] regulator: core: allow consumers to request to closes step voltage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 19 Jun 2013 14:17:54 -0500
From:	Nishanth Menon <nm@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Liam Girdwood <lgirdwood@...il.com>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	Nishanth Menon <nm@...com>
Subject: [RFC PATCH] regulator: core: allow consumers to request to closes step voltage

Regulator consumers are not aware of the characteristics of regulator
used to supply. For example:
consumerX requests for voltage min_uV = 500mV, max_uV = 500mV
On a regulator which has a step size of 10mV, this can be exactly
achieved.

However, on a regulator which is non-exact divider step size (example
12.66mV step size), the closest achievable would be 506.4.
regulator_set_voltage_tol does not work out either as <500mV is not an
operational voltage.

Account for step size accuracy when exact voltage requests are send for
step based regulators.

Signed-off-by: Nishanth Menon <nm@...com>
---
The specific example I faced was using cpufreq-cpu0 driver with voltages
for OPPs for MPU rail and attempting the common definitions against voltages
that are non-exact multiples of stepsize of PMIC.

The alternative would be implement custom set_voltage (as againsta simpler
set_voltage_sel and using linear map/list functions) for the regulator which
will account for the same.

Yet another alternative might be to introduce yet another custom function similar
to regulator_set_voltage_tol which accounts for this. something like:
regulator_set_voltage_floor(regulator, voltage, tol) or something to that effect.

 drivers/regulator/core.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 288c75a..98c96b2 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2407,6 +2407,9 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 		}

 	} else if (rdev->desc->ops->set_voltage_sel) {
+		if (min_uV == max_uV && rdev->desc->uV_step)
+			max_uV += rdev->desc->uV_step;
+
 		if (rdev->desc->ops->map_voltage) {
 			ret = rdev->desc->ops->map_voltage(rdev, min_uV,
 							   max_uV);
-- 
1.7.9.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/