From: Niklas Cassel <niklas.cassel@linaro.org>
To: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Cc: bjorn.andersson@linaro.org, lgirdwood@gmail.com,
broonie@kernel.org, jorge.ramirez-ortiz@linaro.org,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] regulator: qcom_spmi: Fix math of spmi_regulator_set_voltage_time_sel
Date: Thu, 20 Jun 2019 15:55:29 +0200 [thread overview]
Message-ID: <20190620135529.GB16411@centauri> (raw)
In-Reply-To: <20190619185636.10831-1-jeffrey.l.hugo@gmail.com>
On Wed, Jun 19, 2019 at 11:56:36AM -0700, Jeffrey Hugo wrote:
> spmi_regulator_set_voltage_time_sel() calculates the amount of delay
> needed as the result of setting a new voltage. Essentially this is the
> absolute difference of the old and new voltages, divided by the slew rate.
>
> The implementation of spmi_regulator_set_voltage_time_sel() is wrong.
>
> It attempts to calculate the difference in voltages by using the
> difference in selectors and multiplying by the voltage step between
> selectors. This ignores the possibility that the old and new selectors
> might be from different ranges, which have different step values. Also,
> the difference between the selectors may encapsulate N ranges inbetween,
> so a summation of each selector change from old to new would be needed.
>
> Lets avoid all of that complexity, and just get the actual voltage
> represented by both the old and new selector, and use those to directly
> compute the voltage delta. This is more straight forward, and has the
> side benifit of avoiding issues with regulator implementations that don't
> have hardware register support to get the current configured range.
>
> Fixes: e92a4047419c ("regulator: Add QCOM SPMI regulator driver")
> Reported-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> Reported-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
> Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
> ---
> drivers/regulator/qcom_spmi-regulator.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/regulator/qcom_spmi-regulator.c b/drivers/regulator/qcom_spmi-regulator.c
> index 13f83be50076..877df33e0246 100644
> --- a/drivers/regulator/qcom_spmi-regulator.c
> +++ b/drivers/regulator/qcom_spmi-regulator.c
> @@ -813,14 +813,10 @@ static int spmi_regulator_set_voltage_time_sel(struct regulator_dev *rdev,
> unsigned int old_selector, unsigned int new_selector)
> {
> struct spmi_regulator *vreg = rdev_get_drvdata(rdev);
> - const struct spmi_voltage_range *range;
> int diff_uV;
>
> - range = spmi_regulator_find_range(vreg);
> - if (!range)
> - return -EINVAL;
> -
> - diff_uV = abs(new_selector - old_selector) * range->step_uV;
> + diff_uV = abs(spmi_regulator_common_list_voltage(rdev, new_selector) -
> + spmi_regulator_common_list_voltage(rdev, old_selector));
>
> return DIV_ROUND_UP(diff_uV, vreg->slew_rate);
> }
> --
> 2.17.1
>
Tested-by: Niklas Cassel <niklas.cassel@linaro.org>
prev parent reply other threads:[~2019-06-20 13:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-19 18:56 [PATCH] regulator: qcom_spmi: Fix math of spmi_regulator_set_voltage_time_sel Jeffrey Hugo
2019-06-19 19:05 ` Bjorn Andersson
2019-06-19 19:43 ` Jorge Ramirez
2019-06-20 11:54 ` Mark Brown
2019-06-20 13:32 ` Applied "regulator: qcom_spmi: Fix math of spmi_regulator_set_voltage_time_sel" to the regulator tree Mark Brown
2019-06-20 13:55 ` Niklas Cassel [this message]
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