Re: [PATCH v2 1/4] ARM: dts: omap5: Update GPIO with address spaceand interrupts

From: Sebastien Guiriec
Date: Tue Oct 23 2012 - 12:15:24 EST

Hi Benoit and John,

On 10/23/2012 06:07 PM, Benoit Cousson wrote:
On 10/23/2012 05:59 PM, Jon Hunter wrote:

On 10/23/2012 10:09 AM, Benoit Cousson wrote:
On 10/23/2012 04:49 PM, Jon Hunter wrote:
Hi Seb,

On 10/23/2012 03:37 AM, Sebastien Guiriec wrote:
Add base address and interrupt line inside Device Tree data for

Signed-off-by: Sebastien Guiriec <s-guiriec@xxxxxx>
arch/arm/boot/dts/omap5.dtsi | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
index 42c78be..9e39f9f 100644
--- a/arch/arm/boot/dts/omap5.dtsi
+++ b/arch/arm/boot/dts/omap5.dtsi
@@ -104,6 +104,8 @@

gpio1: gpio@4ae10000 {
compatible = "ti,omap4-gpio";
+ reg = <0x4ae10000 0x200>;
+ interrupts = <0 29 0x4>;
ti,hwmods = "gpio1";
#gpio-cells = <2>;

I am wondering if we should add the "interrupt-parent" property to add
nodes in the device-tree source. I know that today the interrupt-parent
is being defined globally, but when device-tree maps an interrupt for a
device it searches for the interrupt-parent starting the current device

So in other words, for gpio1 it will search the gpio1 binding for
"interrupt-parent" and if not found move up a level and search again. It
will keep doing this until it finds the "interrupt-parent".

Therefore, I believe it will improve search time and hence, boot time if
we have interrupt-parent defined in each node.

Mmm, I'm not that sure. it will increase the size of the blob, so
increase the time to load it and then to parse it. Where in the current
case, it is just going up to the parent node using the already
un-flatten tree in memory and thus that should not take that much time.

Yes it will definitely increase the size, so that could slow things down.

That being said, it might be interesting to benchmark that to see what
is the real impact.

Right, I wonder what the key functions are we need to benchmark to get
an overall feel for what is best? Right now I am seeing some people add
the interrupt-parent for device nodes and others not. Ideally we should
be consistent, but at the same time it is probably something that we can
easily sort out later. So not a big deal either way.

For consistency, I'd rather not add it at all for the moment.
Later, when we will only support DT boot, people will start complaining
about the boot time increase and then we will start optimizing a little
bit :-)

I just do it like that to be consistent with what is inside OMAP4 dtsi for those IPs (GPIO/UART/MMC/I2C). Now after checking Peter already add the interrupt-parent for all audio IPs (OMAP3/4/5). But here we need also interrupts name. So here we should try to be consistent.

So I can send back the series for OMAP5 and update the OMAP4 with
interrupts-parent = <&gic>

As of today we are not consistent.


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