* pwm: sun4i: pwm-backlight not working since 5.6-rc1
@ 2020-03-12 12:22 Pascal Roeleven
2020-03-12 13:29 ` Uwe Kleine-König
0 siblings, 1 reply; 6+ messages in thread
From: Pascal Roeleven @ 2020-03-12 12:22 UTC (permalink / raw)
To: Thierry Reding, Uwe Kleine-König, Maxime Ripard,
Chen-Yu Tsai, Philipp Zabel, linux-pwm, linux-arm-kernel,
linux-kernel
Cc: linux-sunxi
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.
Not sure if it helps, but the binding for the backlight is as follows:
backlight: backlight {
compatible = "pwm-backlight";
pwms = <&pwm 0 100000 PWM_POLARITY_INVERTED>;
power-supply = <®_vbat>;
enable-gpios = <&pio 7 7 GPIO_ACTIVE_HIGH>; /* PH7 */
brightness-levels = <0 30 40 50 60 70 80 90 100>;
default-brightness-level = <8>;
};
Please let me know if there is anything else which might be helpful to
know or anything I can test.
Regards,
Pascal
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^ permalink raw reply [flat|nested] 6+ messages in thread* Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 2020-03-12 12:22 pwm: sun4i: pwm-backlight not working since 5.6-rc1 Pascal Roeleven @ 2020-03-12 13:29 ` Uwe Kleine-König 2020-03-12 15:06 ` Pascal Roeleven 0 siblings, 1 reply; 6+ messages in thread From: Uwe Kleine-König @ 2020-03-12 13:29 UTC (permalink / raw) To: Pascal Roeleven Cc: linux-pwm, linux-sunxi, linux-kernel, Maxime Ripard, Chen-Yu Tsai, Thierry Reding, Philipp Zabel, linux-arm-kernel 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/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 2020-03-12 13:29 ` Uwe Kleine-König @ 2020-03-12 15:06 ` Pascal Roeleven 2020-03-16 7:26 ` Uwe Kleine-König 0 siblings, 1 reply; 6+ messages in thread From: Pascal Roeleven @ 2020-03-12 15:06 UTC (permalink / raw) To: Uwe Kleine-König Cc: linux-pwm, linux-sunxi, linux-kernel, Maxime Ripard, Chen-Yu Tsai, Thierry Reding, Philipp Zabel, linux-arm-kernel 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: 00000050 00130014 00000000 (full brightness) 01c20e00: 00000050 00130006 00000000 (min brightness) Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the issue. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 2020-03-12 15:06 ` Pascal Roeleven @ 2020-03-16 7:26 ` Uwe Kleine-König 2020-03-17 17:32 ` Uwe Kleine-König 0 siblings, 1 reply; 6+ messages in thread From: Uwe Kleine-König @ 2020-03-16 7:26 UTC (permalink / raw) To: Pascal Roeleven Cc: linux-pwm, linux-sunxi, linux-kernel, Maxime Ripard, Chen-Yu Tsai, Thierry Reding, Philipp Zabel, linux-arm-kernel 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: 00000050 00130014 00000000 (full brightness) > 01c20e00: 00000050 00130006 00000000 (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/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 2020-03-16 7:26 ` Uwe Kleine-König @ 2020-03-17 17:32 ` Uwe Kleine-König 2020-03-17 17:52 ` Pascal Roeleven 0 siblings, 1 reply; 6+ messages in thread From: Uwe Kleine-König @ 2020-03-17 17:32 UTC (permalink / raw) To: Pascal Roeleven Cc: linux-pwm, linux-sunxi, linux-kernel, Maxime Ripard, Chen-Yu Tsai, Thierry Reding, Philipp Zabel, linux-arm-kernel 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: 00000050 00130014 00000000 (full brightness) > > 01c20e00: 00000050 00130006 00000000 (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/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 2020-03-17 17:32 ` Uwe Kleine-König @ 2020-03-17 17:52 ` Pascal Roeleven 0 siblings, 0 replies; 6+ messages in thread From: Pascal Roeleven @ 2020-03-17 17:52 UTC (permalink / raw) To: Uwe Kleine-König Cc: linux-pwm, linux-sunxi, linux-kernel, Maxime Ripard, Chen-Yu Tsai, Thierry Reding, Philipp Zabel, linux-arm-kernel 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: 00000050 00130014 00000000 (full brightness) >> > 01c20e00: 00000050 00130006 00000000 (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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-03-17 17:53 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2020-03-12 12:22 pwm: sun4i: pwm-backlight not working since 5.6-rc1 Pascal Roeleven 2020-03-12 13:29 ` Uwe Kleine-König 2020-03-12 15:06 ` Pascal Roeleven 2020-03-16 7:26 ` Uwe Kleine-König 2020-03-17 17:32 ` Uwe Kleine-König 2020-03-17 17:52 ` Pascal Roeleven
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