[U-Boot-Users] Do we enable Interrupts in U-Boot?

[Chetan Nanda]

Hi All,
I am using a custom board (similar to MALTA) with MIPS - 4KEC processor on it.
I use u-boot to load linux on our board.

My Question is :
Do we enable interrupt in u-boot code for UART and ETHERNET or we
have running in Polling Mode?

Thanks,
nandac

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[Stefan Roese]

On Tuesday 08 January 2008, Chetan Nanda wrote:
> I am using a custom board (similar to MALTA) with MIPS - 4KEC processor on
> it. I use u-boot to load linux on our board.
>
> My Question is :
> Do we enable interrupt in u-boot code for UART and ETHERNET or we
> have running in Polling Mode?

Normally all this is done in polling mode.

Best regards,
Stefan

=====================================================================
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: off...@denx.de
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[Wolfgang Denk]

In message <7f245da80801080411g4f8...@mail.gmail.com> you wrote:
>
> Do we enable interrupt in u-boot code for UART and ETHERNET or we
> have running in Polling Mode?

I don;t know what you are doing, but I usually use polling mode.

Please see also http://www.denx.de/wiki/view/UBoot/DesignRequirements

Best regards,

Wolfgang Denk

--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de
######## This message was made from 100% recycled electrons. ########

[Chetan Nanda]

In that case there must be some threads that continuously check for
pending requests from UART, ETHERNET or so ..
But I don't find any sort of threading inside u-boot code

[Andreas Schweigstill]

Hello!

Chetan Nanda schrieb:

> In that case there must be some threads that continuously check for
> pending requests from UART, ETHERNET or so ..
> But I don't find any sort of threading inside u-boot code

No, the peripherals get only polled when they are used. That's why
a device running U-Boot usually won't respond to ping/ICMP echo.
Network driver polling only occurs from NetLoop(); this function will
be used only for most (all?) network commands.

U-Boot doesn't implement any kind of threading. Keep in mind that U-Boot
is *not* an operating system but only a bootloader.

There have been lots of requests for some kind of multitasking but it
would be quite time-consuming to implement this without breaking
compatibility with many software parts why rely on the fact that they
have full control over the system when running.

Regards
Andreas Schweigstill

--
Dipl.-Phys. Andreas Schweigstill
Schweigstill IT | Embedded Systems
Schauenburgerstraße 116, D-24118 Kiel, Germany
Phone: (+49) 431 5606-435, Fax: (+49) 431 5606-436
Mobile: (+49) 171 6921973, Web: http://www.schweigstill.de/

[Andreas Schweigstill]

Hello!

Andreas Schweigstill schrieb:

> There have been lots of requests for some kind of multitasking but it
> would be quite time-consuming to implement this without breaking
> compatibility with many software parts why rely on the fact that they
> have full control over the system when running.

And I also forgot to mention that sometimes it is a really big advantage
to rely on no interrupt handlers running in the background. If I want to
test some hardware I usually write a small test program as a U-Boot
command and don't write a Linux or RTOS driver because I need a "bare"
system with a command line processor.

[Stefan Roese]

On Tuesday 08 January 2008, Chetan Nanda wrote:
> In that case there must be some threads that continuously check for
> pending requests from UART, ETHERNET or so ..

Threads? U-Boot is not an full blown OS. No threads are needed in this
bootloader.

> But I don't find any sort of threading inside u-boot code

U-Boot "sits" there and waits for some input from the console, or for an
ethernet reply packet. This can be done using polling without any performance
penalty.

[Chetan Nanda]

On 1/8/08, Stefan Roese <s...@denx.de> wrote:
> On Tuesday 08 January 2008, Chetan Nanda wrote:
> > In that case there must be some threads that continuously check for
> > pending requests from UART, ETHERNET or so ..
>
> Threads? U-Boot is not an full blown OS. No threads are needed in this
> bootloader.
>
> > But I don't find any sort of threading inside u-boot code
>
> U-Boot "sits" there and waits for some input from the console, or for an
> ethernet reply packet. This can be done using polling without any performance
> penalty.
>

Thanks, for explaining the things,
But how can we wait for two events simultaneously (that is also under
a single thread of execution)? Can you give me pointer to the code ?

[Ben Warren]

Chetan Nanda wrote:
> On 1/8/08, Stefan Roese <s...@denx.de> wrote:
>
>> On Tuesday 08 January 2008, Chetan Nanda wrote:
>>
>>> In that case there must be some threads that continuously check for
>>> pending requests from UART, ETHERNET or so ..
>>>
>> Threads? U-Boot is not an full blown OS. No threads are needed in this
>> bootloader.
>>
>>
>>> But I don't find any sort of threading inside u-boot code
>>>
>> U-Boot "sits" there and waits for some input from the console, or for an
>> ethernet reply packet. This can be done using polling without any performance
>> penalty.
>>
>>
> Thanks, for explaining the things,
> But how can we wait for two events simultaneously (that is also under
> a single thread of execution)? Can you give me pointer to the code ?
>

We don't. Everything's single-threaded and poll-based.

regards,
Ben

[Andreas Schweigstill]

Hello!

Chetan Nanda schrieb:

> Thanks, for explaining the things,
> But how can we wait for two events simultaneously (that is also under
> a single thread of execution)? Can you give me pointer to the code ?

As mentioned before, U-Boot is not an operating system which provides
such means. It doesn't have a driver layer with file operations similar
to Linux. The only way to wait for events exactly simultaneously is
using a hardware which provides these events in one hardware register.

Usually one would poll the event sources:

...

while (1) {
if (driver_a_check_data_available()) {
driver_a_read_data();
}
if (driver_b_check_data_available()) {
driver_b_read_data();
}
}

if this will be implemented in an U-Boot command, you probably want
this loop also to be left, e.g. by pressing Ctrl-C:

while (!ctrlc()) {
...
}

Regards
Andreas Schweigstill

--
Dipl.-Phys. Andreas Schweigstill
Schweigstill IT | Embedded Systems
Schauenburgerstraße 116, D-24118 Kiel, Germany
Phone: (+49) 431 5606-435, Fax: (+49) 431 5606-436
Mobile: (+49) 171 6921973, Web: http://www.schweigstill.de/

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