On Thu, Mar 12, 2020 at 01:22:13PM +0100, Pascal Roeleven wrote: > Hi all, > > I am working on adding an old A10 device to mainline and noticed an issue > when testing on 5.5.8 vs master. > > Since 5.6-rc1, I can't control the brightness of my LCD backlight anymore. > The backlight stays on full brightness instead. I am controlling the > brightness value via sysfs for testing. > > I am not sure if this is a general pwm-sun4i issue or if it is related to > the backlight. However I narrowed it down to one commit for pwm-sun4i: > > fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 > > If I use pwm-sun4i.c from 5b090b430d750961305030232314b6acdb0102aa on > master, the backlight works fine. Unfortunately, due to my lack of kernel > experience, I can't see how the commit above broke it.
Hmm, I cannot see how fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 breaks this. Looking at the output of git show -b fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 (i.e. ignoring whitespace changes) I don't see how the behaviour you're reporting can be explained. Are you sure that fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 is the bad commit? Can you install a tool to inspect register values and check how the affected registers change if you switch kernel versions and/or pwm settings? (e.g. memtool md 0x1c20e00+0xc ) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ | -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/linux-sunxi/20200312132942.2kfspvmoc3mxkdx4%40pengutronix.de.