[linux-sunxi] Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1
On 2020-03-17 18:32, Uwe Kleine-König wrote: Hello Pascal, On Mon, Mar 16, 2020 at 08:26:13AM +0100, Uwe Kleine-König wrote: On Thu, Mar 12, 2020 at 04:06:07PM +0100, Pascal Roeleven wrote: > On 2020-03-12 14:29, Uwe Kleine-König wrote: > > 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 > > Thanks for your response. > > Yes I am sure that is the commit. If I am on master, and replace pwm-sun4i.c > with the one from 5b090b43, everything works. If I then apply fa4d8178, it > stops working. > > And strangely the output of the registers is exactly the same before and > after fa4d8178: > > 01c20e00: 0050 00130014 (full brightness) > 01c20e00: 0050 00130006 (min brightness) > > Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the > issue. Very strange. I'm out of sensible ideas. The remaining ones are: - enable tracing in the kernel and boot with trace_event=pwm And then check after the problem occurred in /sys/kernel/debug/tracing/trace if something sticks out. - Try modifying the registers using memtool. E.g. memtool mw 0x01c20e04 0x00130012 - Do you have equipment to check the actual output of the PWM hardware? If so, what do you see? I assume the sun4i-series you sent earlier today resolves the problems you reported here? Best regards Uwe Hi Uwe, Yes it does, but as Emil mentioned it's probably not complete. It's just an RFC for now to make sure it doesn't cause a regression. Turns out the Allwinner PWM controller is even more pickier than I thought. Again, thank you for your help. -- 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/ddd9b9c5b3d28a30c888fdcfc1ac6d64%40pascalroeleven.nl.
[linux-sunxi] Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1
Hello Pascal, On Mon, Mar 16, 2020 at 08:26:13AM +0100, Uwe Kleine-König wrote: > On Thu, Mar 12, 2020 at 04:06:07PM +0100, Pascal Roeleven wrote: > > On 2020-03-12 14:29, Uwe Kleine-König wrote: > > > 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 > > > > Thanks for your response. > > > > Yes I am sure that is the commit. If I am on master, and replace pwm-sun4i.c > > with the one from 5b090b43, everything works. If I then apply fa4d8178, it > > stops working. > > > > And strangely the output of the registers is exactly the same before and > > after fa4d8178: > > > > 01c20e00: 0050 00130014 (full brightness) > > 01c20e00: 0050 00130006 (min brightness) > > > > Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the > > issue. > > Very strange. I'm out of sensible ideas. The remaining ones are: > > - enable tracing in the kernel and boot with > > trace_event=pwm > > And then check after the problem occurred in > /sys/kernel/debug/tracing/trace if something sticks out. > > - Try modifying the registers using memtool. E.g. > > memtool mw 0x01c20e04 0x00130012 > > - Do you have equipment to check the actual output of the PWM hardware? > If so, what do you see? I assume the sun4i-series you sent earlier today resolves the problems you reported here? 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/20200317173208.t5s63pfz3byxsgzi%40pengutronix.de.
[linux-sunxi] Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1
Hello, On Thu, Mar 12, 2020 at 04:06:07PM +0100, Pascal Roeleven wrote: > On 2020-03-12 14:29, Uwe Kleine-König wrote: > > 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 > > Thanks for your response. > > Yes I am sure that is the commit. If I am on master, and replace pwm-sun4i.c > with the one from 5b090b43, everything works. If I then apply fa4d8178, it > stops working. > > And strangely the output of the registers is exactly the same before and > after fa4d8178: > > 01c20e00: 0050 00130014 (full brightness) > 01c20e00: 0050 00130006 (min brightness) > > Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the > issue. Very strange. I'm out of sensible ideas. The remaining ones are: - enable tracing in the kernel and boot with trace_event=pwm And then check after the problem occurred in /sys/kernel/debug/tracing/trace if something sticks out. - Try modifying the registers using memtool. E.g. memtool mw 0x01c20e04 0x00130012 - Do you have equipment to check the actual output of the PWM hardware? If so, what do you see? 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/20200316072613.37lnjfloac4npudf%40pengutronix.de.
[linux-sunxi] Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1
On 2020-03-12 14:29, Uwe Kleine-König wrote: 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 Thanks for your response. Yes I am sure that is the commit. If I am on master, and replace pwm-sun4i.c with the one from 5b090b43, everything works. If I then apply fa4d8178, it stops working. And strangely the output of the registers is exactly the same before and after fa4d8178: 01c20e00: 0050 00130014 (full brightness) 01c20e00: 0050 00130006 (min brightness) Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the issue. -- 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/6e995c4c22c4e6c93acb1f491e5aa109%40pascalroeleven.nl.
[linux-sunxi] Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1
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.
