[PATCH v2 0/4] ARM: dts: Update OMAP5 with address space and interrupts

[PATCH v2 0/4] ARM: dts: Update OMAP5 with address space and interrupts

[Sebastien Guiriec]

Since kernel 3.7 the DTS data are not overwriten by hwmod data we can add the address space
and interrupt line description inside dtsi file for OMAP5. This serie is updating the
current OMAP5 IP with missing entry.

It has been tested on OMAP5 with 3.7-audio-display feature tree.
- MMC is probing and functional
- TWL6041 probing (GPIO/I2C)
- booting (UART)

Update since v1:
- Add Ack and review
- Fix up commit messages.

Sebastien Guiriec (4):
  ARM: dts: omap5: Update GPIO with address space and interrupts
  ARM: dts: omap5: Update I2C with address space and interrupts
  ARM: dts: omap5: Update UART with address space and interrupts
  ARM: dts: omap5: Update MMC with address space and interrupts

 arch/arm/boot/dts/omap5.dtsi |   56 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 4 deletions(-)

-- 
1.7.10.4

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

[Sebastien Guiriec]

Add base address and interrupt line inside Device Tree data for
OMAP5

Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
---
 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-controller;
 			#gpio-cells = <2>;
@@ -113,6 +115,8 @@
 
 		gpio2: gpio@48055000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x48055000 0x200>;
+			interrupts = <0 30 0x4>;
 			ti,hwmods = "gpio2";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -122,6 +126,8 @@
 
 		gpio3: gpio@48057000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x48057000 0x200>;
+			interrupts = <0 31 0x4>;
 			ti,hwmods = "gpio3";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -131,6 +137,8 @@
 
 		gpio4: gpio@48059000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x48059000 0x200>;
+			interrupts = <0 32 0x4>;
 			ti,hwmods = "gpio4";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -140,6 +148,8 @@
 
 		gpio5: gpio@4805b000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x4805b000 0x200>;
+			interrupts = <0 33 0x4>;
 			ti,hwmods = "gpio5";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -149,6 +159,8 @@
 
 		gpio6: gpio@4805d000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x4805d000 0x200>;
+			interrupts = <0 34 0x4>;
 			ti,hwmods = "gpio6";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -158,6 +170,8 @@
 
 		gpio7: gpio@48051000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x48051000 0x200>;
+			interrupts = <0 35 0x4>;
 			ti,hwmods = "gpio7";
 			gpio-controller;
 			#gpio-cells = <2>;
@@ -167,6 +181,8 @@
 
 		gpio8: gpio@48053000 {
 			compatible = "ti,omap4-gpio";
+			reg = <0x48053000 0x200>;
+			interrupts = <0 121 0x4>;
 			ti,hwmods = "gpio8";
 			gpio-controller;
 			#gpio-cells = <2>;
-- 
1.7.10.4

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

[Jon Hunter]

Hi Seb,

On 10/23/2012 03:37 AM, Sebastien Guiriec wrote:
> Add base address and interrupt line inside Device Tree data for
> OMAP5
> 
> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
> ---
>  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-controller;
>  			#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
node.

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.

Cheers
Jon

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

[Benoit Cousson]

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
>> OMAP5
>>
>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>> ---
>>  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-controller;
>>  			#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
> node.
> 
> 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.

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

Regards,
Benoit

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

[Jon Hunter]

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
>>> OMAP5
>>>
>>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>>> ---
>>>  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-controller;
>>>  			#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
>> node.
>>
>> 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.

Cheers
Jon

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

[Benoit Cousson]

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
>>>> OMAP5
>>>>
>>>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>>>> ---
>>>>  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-controller;
>>>>  			#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
>>> node.
>>>
>>> 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 :-)

Regards,
Benoit

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

[Sebastien Guiriec]

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
>>>>> OMAP5
>>>>>
>>>>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>>>>> ---
>>>>>   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-controller;
>>>>>   			#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
>>>> node.
>>>>
>>>> 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.

>
> Regards,
> Benoit
>
>

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

[Benoit Cousson]

On 10/23/2012 06:15 PM, Sebastien Guiriec wrote:
> 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
>>>>>> OMAP5
>>>>>>
>>>>>> Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
>>>>>> ---
>>>>>>   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-controller;
>>>>>>               #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
>>>>> node.
>>>>>
>>>>> 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>

No, you should not, as explained previously. You'd better remove the one
already in audio IPs for consistency.


Regards,
Benoit

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

[Mitch Bradley]

On 10/23/2012 4:49 AM, Jon Hunter wrote:

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

I strongly suspect (based on many years of performance tuning, with
special focus on boot time) that the time difference will be completely
insignificant.  The total extra time for walking up the interrupt tree
for every interrupt in a large system is comparable to the time it takes
to send a few characters out a UART.  So you can get more improvement
from eliminating a single printk() than from globally adding per-node
interrupt-parent.

Furthermore, the cost of processing all of the interrupt-parent
properties is probably similar to the cost of the avoided tree walks.

CPU cycles are very fast compared to I/O register accesses, say a factor
of 100.  Now consider that many modern devices contain embedded
microcontrollers (SD cards, network interface modules, USB hubs and
devices, ...), and those devices usually require various delays measured
in milliseconds, to ensure that the microcontroller is ready for the
next initialization step.  Those delays are extremely long compared to
CPU cycles.  Obviously, some of that can be overlapped by careful
multithreading, but that isn't free either.

The bottom line is that I'm pretty sure that adding per-node
interrupt-parent would not be worthwhile from the standpoint of speeding
up boot time.

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

[Jon Hunter]

Hi Mitch,

On 10/23/2012 11:55 AM, Mitch Bradley wrote:
> On 10/23/2012 4:49 AM, Jon Hunter wrote:
> 
>> Therefore, I believe it will improve search time and hence, boot time if
>> we have interrupt-parent defined in each node.
> 
> I strongly suspect (based on many years of performance tuning, with
> special focus on boot time) that the time difference will be completely
> insignificant.  The total extra time for walking up the interrupt tree
> for every interrupt in a large system is comparable to the time it takes
> to send a few characters out a UART.  So you can get more improvement
> from eliminating a single printk() than from globally adding per-node
> interrupt-parent.
> 
> Furthermore, the cost of processing all of the interrupt-parent
> properties is probably similar to the cost of the avoided tree walks.
> 
> CPU cycles are very fast compared to I/O register accesses, say a factor
> of 100.  Now consider that many modern devices contain embedded
> microcontrollers (SD cards, network interface modules, USB hubs and
> devices, ...), and those devices usually require various delays measured
> in milliseconds, to ensure that the microcontroller is ready for the
> next initialization step.  Those delays are extremely long compared to
> CPU cycles.  Obviously, some of that can be overlapped by careful
> multithreading, but that isn't free either.
> 
> The bottom line is that I'm pretty sure that adding per-node
> interrupt-parent would not be worthwhile from the standpoint of speeding
> up boot time.

Absolutely, I don't expect this to miraculously improve the boot time or
suggest that this is a major contributor to boot time, but what is the
best approach in general in terms of efficiency (memory and time). In
other words, is there a best practice? And from your feedback, I
understand that adding a global interrupt-parent is a good practice.

For a bit of fun, I took an omap4430 board and benchmarked the time
taken by the of_irq_find_parent() when interrupt-parent was defined for
each node using interrupts and without.

There were a total of 47 device nodes using interrupts. Adding the
interrupt-parent to all 47 nodes increased the dtb from 13211 bytes to
13963 bytes.

On boot-up I saw 117 calls to of_irq_find_parent() for this platform
(there appears to be multiple calls for a given device). Without
interrupt-parent defined for each node total time spent in
of_irq_find_parent() was 1.028 ms where as with interrupt-parent defined
for each node the total time was 0.4032 ms. This was done using a
38.4MHz timer and the overhead of reading the timer 117 times was about
36 us.

I understand that this does not provide the full picture, but I wanted
to get a better handle on the times here. So yes the overall overhead
here is not significant for us to worry about.

Cheers
Jon

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

[Mitch Bradley]

On 10/23/2012 1:15 PM, Jon Hunter wrote:
> Hi Mitch,
> 
> On 10/23/2012 11:55 AM, Mitch Bradley wrote:
>> On 10/23/2012 4:49 AM, Jon Hunter wrote:
>>
>>> Therefore, I believe it will improve search time and hence, boot time if
>>> we have interrupt-parent defined in each node.
>>
>> I strongly suspect (based on many years of performance tuning, with
>> special focus on boot time) that the time difference will be completely
>> insignificant.  The total extra time for walking up the interrupt tree
>> for every interrupt in a large system is comparable to the time it takes
>> to send a few characters out a UART.  So you can get more improvement
>> from eliminating a single printk() than from globally adding per-node
>> interrupt-parent.
>>
>> Furthermore, the cost of processing all of the interrupt-parent
>> properties is probably similar to the cost of the avoided tree walks.
>>
>> CPU cycles are very fast compared to I/O register accesses, say a factor
>> of 100.  Now consider that many modern devices contain embedded
>> microcontrollers (SD cards, network interface modules, USB hubs and
>> devices, ...), and those devices usually require various delays measured
>> in milliseconds, to ensure that the microcontroller is ready for the
>> next initialization step.  Those delays are extremely long compared to
>> CPU cycles.  Obviously, some of that can be overlapped by careful
>> multithreading, but that isn't free either.
>>
>> The bottom line is that I'm pretty sure that adding per-node
>> interrupt-parent would not be worthwhile from the standpoint of speeding
>> up boot time.
> 
> Absolutely, I don't expect this to miraculously improve the boot time or
> suggest that this is a major contributor to boot time, but what is the
> best approach in general in terms of efficiency (memory and time). In
> other words, is there a best practice? And from your feedback, I
> understand that adding a global interrupt-parent is a good practice.

>From a maintenance standpoint, "saying it once" is best practice.  Time
that you don't spend doing unnecessary maintenance can be spent looking
for other, higher value, improvements.  And when you do need to optimize
something, it's much easier if the function is centralized.

Pushing the interrupt parent up the tree to the appropriate point can
make the next platform easier, opening the possibility of changing just
one thing instead of several dozen.

There have been several cases when I have violated good factoring in
order to save a little time, only to have to undo it later when the next
system was enough different that the de-factored version didn't work.

So, while there are certainly cases where you are forced to do
otherwise, I generally like the "don't repeat yourself" mantra.

> 
> For a bit of fun, I took an omap4430 board and benchmarked the time
> taken by the of_irq_find_parent() when interrupt-parent was defined for
> each node using interrupts and without.
> 
> There were a total of 47 device nodes using interrupts. Adding the
> interrupt-parent to all 47 nodes increased the dtb from 13211 bytes to
> 13963 bytes.
> 
> On boot-up I saw 117 calls to of_irq_find_parent() for this platform
> (there appears to be multiple calls for a given device). Without
> interrupt-parent defined for each node total time spent in
> of_irq_find_parent() was 1.028 ms where as with interrupt-parent defined
> for each node the total time was 0.4032 ms. This was done using a
> 38.4MHz timer and the overhead of reading the timer 117 times was about
> 36 us.

That sounds about right.  The savings of 600 us is 6 characters at
115200 baud.

> 
> I understand that this does not provide the full picture, but I wanted
> to get a better handle on the times here. So yes the overall overhead
> here is not significant for us to worry about.

Big ticket items for boot time improvement are time spent waiting for
peripheral devices to become ready and time spent spewing diagnostic
messages.  But in the final analysis, you just have to measure what is
happening and see what you can do to improve it.  In my experience, CPU
cycles are rarely problematic, unless they are artificially slowed down
due to caches being off or due to direct execution from slow memory like
ROMs.

I once shaved an hour off the startup time for a PowerPC system by
moving some critical code into cache.  This was on a prototype "chip"
that was being emulated by arrays of FPGAs.

On the first generation OLPC XO-1 machine we were really interested in
super-fast wakeup from suspend.  I tuned that firmware code path to the
nth degree, finally getting stuck at 2 ms because you had to wait that
long before accessing the PCI bus interface, otherwise the SD controller
chip would lock up.  Then I transferred control to the kernel, which had
to wait something like 40 ms (two display frame times) to re-sync the
video subsystem, then it had to re-enable the USB subsystem, which ended
up taking a good fraction of a second.

Things haven't gotten much better (in fact they are probably worse),
because, even the the CPUs have gotten faster, there are more
peripherals with hard-to-avoid delays.  So, in the end, a few
sub-millisecond delays just don't matter.

> 
> Cheers
> Jon
> 
> 

[PATCH v2 2/4] ARM: dts: omap5: Update I2C with address space and interrupts

[Sebastien Guiriec]

Add base address and interrupt line inside Device Tree data for
OMAP5

Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
Reviewed-by: Shubhrajyoti D <shubhrajyoti@ti.com>
---
 arch/arm/boot/dts/omap5.dtsi |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
index 9e39f9f..6c22e1b 100644
--- a/arch/arm/boot/dts/omap5.dtsi
+++ b/arch/arm/boot/dts/omap5.dtsi
@@ -192,6 +192,8 @@
 
 		i2c1: i2c@48070000 {
 			compatible = "ti,omap4-i2c";
+			reg = <0x48070000 0x100>;
+			interrupts = <0 56 0x4>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			ti,hwmods = "i2c1";
@@ -199,6 +201,8 @@
 
 		i2c2: i2c@48072000 {
 			compatible = "ti,omap4-i2c";
+			reg = <0x48072000 0x100>;
+			interrupts = <0 57 0x4>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			ti,hwmods = "i2c2";
@@ -206,20 +210,26 @@
 
 		i2c3: i2c@48060000 {
 			compatible = "ti,omap4-i2c";
+			reg = <0x48060000 0x100>;
+			interrupts = <0 61 0x4>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			ti,hwmods = "i2c3";
 		};
 
-		i2c4: i2c@4807A000 {
+		i2c4: i2c@4807a000 {
 			compatible = "ti,omap4-i2c";
+			reg = <0x4807a000 0x100>;
+			interrupts = <0 62 0x4>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			ti,hwmods = "i2c4";
 		};
 
-		i2c5: i2c@4807C000 {
+		i2c5: i2c@4807c000 {
 			compatible = "ti,omap4-i2c";
+			reg = <0x4807c000 0x100>;
+			interrupts = <0 60 0x4>;
 			#address-cells = <1>;
 			#size-cells = <0>;
 			ti,hwmods = "i2c5";
-- 
1.7.10.4

[PATCH v2 3/4] ARM: dts: omap5: Update UART with address space and interrupts

[Sebastien Guiriec]

Add base address and interrupt line inside Device Tree data for
OMAP5.

Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
Reviewed-by: Shubhrajyoti D <shubhrajyoti@ti.com>
---
 arch/arm/boot/dts/omap5.dtsi |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
index 6c22e1b..413df94 100644
--- a/arch/arm/boot/dts/omap5.dtsi
+++ b/arch/arm/boot/dts/omap5.dtsi
@@ -237,36 +237,48 @@
 
 		uart1: serial@4806a000 {
 			compatible = "ti,omap4-uart";
+			reg = <0x4806a000 0x100>;
+			interrupts = <0 72 0x4>;
 			ti,hwmods = "uart1";
 			clock-frequency = <48000000>;
 		};
 
 		uart2: serial@4806c000 {
 			compatible = "ti,omap4-uart";
+			reg = <0x4806c000 0x100>;
+			interrupts = <0 73 0x4>;
 			ti,hwmods = "uart2";
 			clock-frequency = <48000000>;
 		};
 
 		uart3: serial@48020000 {
 			compatible = "ti,omap4-uart";
+			reg = <0x48020000 0x100>;
+			interrupts = <0 74 0x4>;
 			ti,hwmods = "uart3";
 			clock-frequency = <48000000>;
 		};
 
 		uart4: serial@4806e000 {
 			compatible = "ti,omap4-uart";
+			reg = <0x4806e000 0x100>;
+			interrupts = <0 70 0x4>;
 			ti,hwmods = "uart4";
 			clock-frequency = <48000000>;
 		};
 
 		uart5: serial@48066000 {
-			compatible = "ti,omap5-uart";
+			compatible = "ti,omap4-uart";
+			reg = <0x48066000 0x100>;
+			interrupts = <0 105 0x4>;
 			ti,hwmods = "uart5";
 			clock-frequency = <48000000>;
 		};
 
 		uart6: serial@48068000 {
-			compatible = "ti,omap6-uart";
+			compatible = "ti,omap4-uart";
+			reg = <0x48068000 0x100>;
+			interrupts = <0 106 0x4>;
 			ti,hwmods = "uart6";
 			clock-frequency = <48000000>;
 		};
-- 
1.7.10.4

[PATCH v2 4/4] ARM: dts: omap5: Update MMC with address space and interrupts

[Sebastien Guiriec]

Add base address and interrupt line inside Device Tree data for
OMAP5.

Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
---
 arch/arm/boot/dts/omap5.dtsi |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
index 413df94..b643cd3 100644
--- a/arch/arm/boot/dts/omap5.dtsi
+++ b/arch/arm/boot/dts/omap5.dtsi
@@ -285,6 +285,8 @@
 
 		mmc1: mmc@4809c000 {
 			compatible = "ti,omap4-hsmmc";
+			reg = <0x4809c000 0x400>;
+			interrupts = <0 83 0x4>;
 			ti,hwmods = "mmc1";
 			ti,dual-volt;
 			ti,needs-special-reset;
@@ -292,24 +294,32 @@
 
 		mmc2: mmc@480b4000 {
 			compatible = "ti,omap4-hsmmc";
+			reg = <0x480b4000 0x400>;
+			interrupts = <0 86 0x4>;
 			ti,hwmods = "mmc2";
 			ti,needs-special-reset;
 		};
 
 		mmc3: mmc@480ad000 {
 			compatible = "ti,omap4-hsmmc";
+			reg = <0x480ad000 0x400>;
+			interrupts = <0 94 0x4>;
 			ti,hwmods = "mmc3";
 			ti,needs-special-reset;
 		};
 
 		mmc4: mmc@480d1000 {
 			compatible = "ti,omap4-hsmmc";
+			reg = <0x480d1000 0x400>;
+			interrupts = <0 96 0x4>;
 			ti,hwmods = "mmc4";
 			ti,needs-special-reset;
 		};
 
 		mmc5: mmc@480d5000 {
 			compatible = "ti,omap4-hsmmc";
+			reg = <0x480d5000 0x400>;
+			interrupts = <0 59 0x4>;
 			ti,hwmods = "mmc5";
 			ti,needs-special-reset;
 		};
-- 
1.7.10.4