Re: [PATCH v2 2/2] leds: add Qualcomm PM8941 WLED driver

[Bjorn Andersson <bjorn@kryo.se>]

On Thu, Feb 12, 2015 at 8:26 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
> On 01/23/15 16:54, Bjorn Andersson wrote:
>> +
>> +static int pm8941_wled_set(struct led_classdev *cdev,
>> +                        enum led_brightness value)
>> +{
>> +     struct pm8941_wled *wled;
>> +     u8 ctrl = 0;
>> +     u16 val;
>> +     int rc;
>> +     int i;
>> +
>> +     wled = container_of(cdev, struct pm8941_wled, cdev);
>> +
>> +     if (value != 0)
>> +             ctrl = PM8941_WLED_REG_MOD_EN_BIT;
>> +
>> +     val = value * PM8941_WLED_REG_VAL_MAX / LED_FULL;
>> +
>> +     rc = regmap_update_bits(wled->regmap,
>> +                     wled->addr + PM8941_WLED_REG_MOD_EN,
>> +                     PM8941_WLED_REG_MOD_EN_MASK, ctrl);
>> +     if (rc)
>> +             return rc;
>> +
>> +     for (i = 0; i < wled->cfg.num_strings; ++i) {
>> +             u8 v[2] = { val & 0xff, (val >> 8) & 0xf };
>> +
>> +             rc = regmap_bulk_write(wled->regmap,
>> +                             wled->addr + PM8941_WLED_REG_VAL_BASE + 2 * i,
>> +                             v, 2);
>> +             if (rc)
>> +                     return rc;
>> +     }
>> +
>> +     rc = regmap_update_bits(wled->regmap,
>> +                     wled->addr + PM8941_WLED_REG_SYNC,
>> +                     PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_ALL);
>> +     if (rc)
>> +             return rc;
>> +
>> +     rc = regmap_update_bits(wled->regmap,
>> +                     wled->addr + PM8941_WLED_REG_SYNC,
>> +                     PM8941_WLED_REG_SYNC_MASK, PM8941_WLED_REG_SYNC_CLEAR);
>> +     return rc;
>> +}
>
> This doesn't seem to do anything for the OVP spike mentioned in this
> patch[1]. Do you see that problem on your device? I imagine the PMIC is
> the same.
>
> [1]
> https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?id=fef9e15072562f0f28dc7066dcdd69388df81ed3
>

That's odd, I can't find that fix in any officially supported releases
for 8974 - which Courtney used as reference for this driver.

Just to make sure I understand the solution; when disabling the sinks
the over-voltage-protection sometimes triggers, so we should detect
that and reset the ovp configuration?

I presume the side effect would be that the sinks would not give any
output until this is done?

Regards,
Bjorn