Re: [PATCH] ARM: dts: r8a7791: Don't disable referenced optional clocks
From: Sergei Shtylyov
Date: Thu Apr 07 2016 - 15:14:37 EST
Hello.
On 04/07/2016 10:00 AM, Sjoerd Simons wrote:
Hey Sergei,
Thanks for your review.
You're welcome. :-)
On Thu, 2016-04-07 at 02:15 +0300, Sergei Shtylyov wrote:
On 04/06/2016 03:52 PM, Sjoerd Simons wrote:
clk_get on a disabled clock node will return EPROBE_DEFER, which
can
cause drivers to be deferred forever if such clocks are referenced
in
their clocks property.
Update the various disabled external clock nodes to default to a
frequency of 0, but don't disable them to prevent this.
Signed-off-by: Sjoerd Simons <sjoerd.simons@xxxxxxxxxxxxxxx>
---
arch/arm/boot/dts/r8a7791-koelsch.dts | 1 +
arch/arm/boot/dts/r8a7791-porter.dts | 1 +
arch/arm/boot/dts/r8a7791.dtsi | 5 +----
3 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm/boot/dts/r8a7791-koelsch.dts
b/arch/arm/boot/dts/r8a7791-koelsch.dts
index 1adf877..da59c28 100644
--- a/arch/arm/boot/dts/r8a7791-koelsch.dts
+++ b/arch/arm/boot/dts/r8a7791-koelsch.dts
@@ -660,6 +660,7 @@
};
&pcie_bus_clk {
+ clock-frequency = <100000000>;
Hmmm, looking at the Koelsch schematics, I don't see this clock.
:-/
I don't have the schematics so i was simply keeping the current state.
I understand. I was just surprised by what checking the code against the
schematics revealed.
I've added Phil Edworthy to the list as he was the one originally
I should've CC'ed Phil myself...
enable the bus clk for Koelsh according to git. Hopefully he can
clarify :)
Let's hope he'd reply...
status = "okay";
};
diff --git a/arch/arm/boot/dts/r8a7791-porter.dts
b/arch/arm/boot/dts/r8a7791-porter.dts
index 9554d13..19b257e 100644
--- a/arch/arm/boot/dts/r8a7791-porter.dts
+++ b/arch/arm/boot/dts/r8a7791-porter.dts
@@ -413,6 +413,7 @@
};
&pcie_bus_clk {
+ clock-frequency = <100000000>;
status = "okay";
};
Again, looking at the Porter schematics, I don't see this clock
either. :-/
You were the one enabling this clock for Porter ;) I don't have PCIE
Yes, of course. I don't remember the gory details already -- I might have
blindly copied what was in the Koelsch's .dts.
hardware to test with on my porter board, might be worth if you could
disable this clock and see if PCI-E still fucntions as expected (maybe
in practise it just happens to prefer the internal clock?) ?
I know the PCIe driver does require this clock in order to function -- it
would be the same eternal -EPROBE_DEFER condition you'd already described;
see drivers/pci/host/pcie-rcar.c yourself...
diff --git a/arch/arm/boot/dts/r8a7791.dtsi
b/arch/arm/boot/dts/r8a7791.dtsi
index 8693888..676df63 100644
--- a/arch/arm/boot/dts/r8a7791.dtsi
+++ b/arch/arm/boot/dts/r8a7791.dtsi
@@ -1104,8 +1104,7 @@
pcie_bus_clk: pcie_bus {
compatible = "fixed-clock";
#clock-cells = <0>;
- clock-frequency = <100000000>;
- status = "disabled";
+ clock-frequency = <0>;
If the clock has a good default frequency, I don't think you need
to
remove it. Otherwise you missed USB_EXTAL which is 48 MHz (and can be
overridden).
I did that as it was by default disabled, so if i do enable it but
don't drop the default frequency to 0 board swithout that clock will
suddenly have it added to their dtb.
Zero frequency is hardly any better then the default...
For the usb external clock I didn't touch it as it was already enabled
by default with a proper frequency, so it wouldn't hit the issue i was
trying to fix here. But i agree, both looking at other Renesas dtsis
and how all other external clocks are done in this dtsi, this node is
odd.
It's not that odd given that the R-Car gen2 manual specifically says it
should be 48 MHz.
Looking into the manual again, the PCIe bus clock must be the onne
presented on the CICREF[PN]1_SATA/PCIe input signals and it indeed should be
100 MHz... So Phil was correct.
MBR, Sergei