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Date: Tue, 28 Jan 2014 18:02:45 +0100
From: Christoph Fritz <chf.fritz@...glemail.com>
To: Tero Kristo <t-kristo@...com>
Cc: Tomi Valkeinen <tomi.valkeinen@...com>,
Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
linux-kernel@...r.kernel.org, pali.rohar@...il.com, pavel@....cz,
Nishanth Menon <nm@...com>
Subject: Re: [BISECTED] OMAP: DSS: clk rate mismatch
On Tue, 2014-01-28 at 15:40 +0200, Tero Kristo wrote:
> On 01/28/2014 11:48 AM, Tomi Valkeinen wrote:
> > On 2014-01-28 11:35, Christoph Fritz wrote:
> >> On Tue, 2014-01-28 at 11:04 +0200, Tomi Valkeinen wrote:
> >>> On 2014-01-27 20:41, Christoph Fritz wrote:
> >>>> On Mon, 2014-01-27 at 19:30 +0200, Ivaylo Dimitrov wrote:
> >>>>> linux-next-20140124 DSS is broken on N900 - display stays black (there
> >>>>> is some noise though). I booted the kernel with qemu and it gives the
> >>>>> following warning:
> >>>>>
> >>>>> [ 0.623779] DSS: set fck to 172800000
> >>>>> [ 0.624237] ------------[ cut here ]------------
> >>>>> [ 0.624298] WARNING: CPU: 0 PID: 1 at
> >>>>> drivers/video/omap2/dss/dss.c:497 dss_set_fck_rate+0x68/0x8c()
> >>>>> [ 0.624359] clk rate mismatch: 288000000 != 172800000
> >>>>
> >>>> Here are also clock regressions since next-20140122 regarding
> >>>> dss_set_fck_rate() and sys_clkout2 occuring in my current patchset for a
> >>>> dm37xx100 board. Please see here:
> >>>
> >>> I presume you get a similar warning on your board? What rates does it
> >>> report?
> >>
> >> None, dss_set_fck_rate() just fails so omapdss_dss exits with error -22.
> >
> > Ok, then it's something else. That means clk_set_rate() fails.
> >
> > If you can do some tests, you could print the rate that the
> > dss_set_fck_rate() is given, to see that it's something reasonable, and
> > also do a clk_get_rate(dss.dss_clk) to see that the clock itself is ok
> > and there's some valid rate there.
> >
> >> To quote the cover-letter[1] of my board-support patch series here:
> >>
> >> Due to a regression since next-20140122 the following errors are present:
> >>
> >> - pin sys_clkout2, which gets configured to 24 Mhz by the fourth patch
> >> in this set, erroneously outputs only 12 Mhz.
> >> Just out of curiosity, configuring it to 48 Mhz puts out desired 24 Mhz.
> >>
> >> - omap_dss, which gets configured by the third patch in this set, fails
> >> to do 'dss_set_fck_rate(fck);' in
> >> drivers/video/omap2/dss/dss.c:dss_setup_default_clock() which leads to:
> >>
> >> | omapdss_dss: probe of omapdss_dss failed with error -22
> >> | omapdss CORE error: Failed to initialize DSS platform driver
> >> | panel-dpi panel-dpi.0: failed to find video source 'dpi.0
> >>
> >> Both regressions seem to have something to do with the clock framework.
> >> Could this be related to the DT clock conversion patches?
> >
> > No idea...
>
> Yea its definitely possible, as the clock DT conversion touches pretty
> much everything. Have you tried whether this works properly with legacy
> boot? Personally I don't have access to any omap3 devices that would
> have display and have no possibility to check this out myself. Anyway,
> my initial guess is that some clock divider setup might be wrong with
> omap3, or we are missing some ti,set-rate-parent flag for some clock
> node which prevents escalating clk_set_rate properly. However, it should
> be easy to debug this by looking at the clock node in question, and its
> parent nodes to see if there are any problems.
Currently I only analyzed sys_clkout2 (see attachments for full
clk_summary files):
clk_summary__next-20140115__works_as_expected:
dpll4_m2_ck 1 1 96000000
dpll4_m2x2_ck 1 1 96000000
omap_192m_alwon_fck 1 1 96000000
omap_96m_alwon_fck 1 2 96000000
per_96m_fck 0 6 96000000
mcbsp4_fck 0 1 96000000
mcbsp3_fck 0 2 96000000
mcbsp2_fck 0 2 96000000
cm_96m_fck 2 3 96000000
clkout2_src_ck 1 1 96000000
sys_clkout2 1 1 24000000
For real, on pin sys_clkout2 are correctly 24 Mhz measured.
clk_summary__next-20140124__sysclkout2_dss_fails:
dpll4_m2_ck 1 1 96000000
dpll4_m2x2_mul_ck 1 1 192000000
dpll4_m2x2_ck 1 1 192000000
omap_192m_alwon_fck 0 0 192000000
omap_96m_alwon_fck 1 2 192000000
per_96m_fck 0 6 192000000
mcbsp4_fck 0 1 192000000
mcbsp3_fck 0 2 192000000
mcbsp2_fck 0 2 192000000
cm_96m_fck 2 3 192000000
clkout2_src_ck 1 1 192000000
sys_clkout2 1 1 24000000
For real, on pin sys_clkout2 are only ~12 Mhz measured.
So I added this patch:
>From c1f8a2aa60cb8973f7eeeb517fb067b1fce66c1f Mon Sep 17 00:00:00 2001
From: Christoph Fritz <chf.fritz@...glemail.com>
Date: Tue, 28 Jan 2014 17:35:10 +0100
Subject: [PATCH] ARM: dts: fix omap3 clock multiplier for dpll4_m2x2_ck
Before DT clock conversion, there was no multiplier for dpll4_m2x2_ck.
So to be compatible again, set dpll4_m2x2_mul_ck multiplier back to 1.
---
arch/arm/boot/dts/omap3xxx-clocks.dtsi | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/boot/dts/omap3xxx-clocks.dtsi b/arch/arm/boot/dts/omap3xxx-clocks.dtsi
index cb04d4b..b594050 100644
--- a/arch/arm/boot/dts/omap3xxx-clocks.dtsi
+++ b/arch/arm/boot/dts/omap3xxx-clocks.dtsi
@@ -212,7 +212,7 @@
#clock-cells = <0>;
compatible = "fixed-factor-clock";
clocks = <&dpll4_m2_ck>;
- clock-mult = <2>;
+ clock-mult = <1>;
clock-div = <1>;
};
--
And it works again. But due to the fact that sys_clkout2 was at 12 Mhz
instead of 24, shouldn't it have been at 48 caused by "clock-mult = 2 ?
Thanks
-- Christoph
View attachment "clk_summary__next-20140115__works_as_expected.txt" of type "text/plain" (14779 bytes)
View attachment "clk_summary__next-20140124__sysclkout2_dss_fails.txt" of type "text/plain" (16501 bytes)
View attachment "clk_summary_diff.txt" of type "text/plain" (22757 bytes)
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