On 2022-01-28 18:50:42, Bjorn Andersson wrote: > On Wed 27 Oct 16:19 CDT 2021, Marijn Suijten wrote: > > > Hi Bjorn, > > > > On 2021-10-22 10:25:35, Bjorn Andersson wrote: > > > On Sat 09 Oct 21:39 PDT 2021, Bjorn Andersson wrote: > > > > > > > The Light Pulse Generator (LPG) is a PWM-block found in a wide range of > > > > PMICs from Qualcomm. These PMICs typically comes with 1-8 LPG instances, > > > > with their output being routed to various other components, such as > > > > current sinks or GPIOs. > > > > > > > > Each LPG instance can operate on fixed parameters or based on a shared > > > > lookup-table, altering the duty cycle over time. This provides the means > > > > for hardware assisted transitions of LED brightness. > > > > > > > > A typical use case for the fixed parameter mode is to drive a PWM > > > > backlight control signal, the driver therefor allows each LPG instance > > > > to be exposed to the kernel either through the LED framework or the PWM > > > > framework. > > > > > > > > A typical use case for the LED configuration is to drive RGB LEDs in > > > > smartphones etc, for which the driver support multiple channels to be > > > > ganged up to a MULTICOLOR LED. In this configuration the pattern > > > > generators will be synchronized, to allow for multi-color patterns. > > > > > > > > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> > > > > --- > > > > > > Any feedback on this? > > > > I asked in #linux-msm whether anything is wrong with the patterns, > > since my Sony Discovery (sdm630 with a pm660l) blinks way quicker on a > > pattern that's supposed to stay on for 1s and off for 1s: > > > > echo "0 1000 255 1000" > /sys/class/leds/rgb\:status/hw_pattern > > > > It however seems to be broken in the same way on an older version now > > (this might be v9 or v8) which I don't remember to be the case. Can you > > double-check if this is all working fine on your side? If so, I'll have > > to find some time to debug it on my end. > > > > I had missed the fact that LPG_RAMP_DURATION_REG is two registers for > msg and lsb, for a total of 9 bits of duration. So what you saw was > probably ticking at 232ms. > > Note though that the pattern uses the last time as "high pause", so I > expect that you should have seen 232 ms of off, followed by 464ms of > light. Visual inspection seems to confirm those numbers indeed! > I've fixed this for v11, both rejecting invalid input and writing out > all 9 bits. Doesn't that 512ms limit, together with using only the last value for hi_pause (and not the first value for lo_pause) force users to write patterns in a certain way which is not easily conveyed to the caller except by reading the comment in the driver? I'd guess lo_pause can be used even if not in ping-pong mode, it should just hold at the first value for the given duration? (That said hw_pattern is anyway already riddled with device-specific information, such as only having one `delta_t` which functions as the step size for every entry, and with the change above would need to be sourced from another step that's not the first.) Bit of a stretch, but perhaps worth noting anyway: should this be written in documentation somewhere, together with pattern examples and their desired outcome to function as testcases too? - Marijn
