[U-Boot] PrimeCell Peripherals

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello all,

the board I'm porting U-Boot on, has several peripheral devices, which
are, according to datasheet, are based on PrimeCell PLxx blocks (for
example, vector interrupt controller is PL190 based; GPIOs are based
on PL061 block and so on). I understand that PrimeCells are IP cores,
which build up a variety of controllers for peripherals.

Therefore I wonder, how well does U-Boot support ARM's PrimeCell
peripherals? Greping sources gave only a couple of hits. I think these
basic controllers like GPIO, interrupt controller etc., which are
widely used on many ARM based platforms (i.e. (AMBA bus-compliant),
but marked in U-Boot sources with different names or so ?

Thanks in advance.

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Hebbar]

Hi,


>>how well does U-Boot support ARM's PrimeCell peripherals?
What do u mean by support. 

I use U-booot as The Primary Bootloader on arm926ej-s based Board.

By Default U-boot supports few Primecell peripherals drivers like PL0x1
UART. 

I developed few others my self, like pl18x mmc, rtc, gpio.

I recently sent a patch for RTC pl031. 

U too can contribute if u can send patch's for other peripherals.

Regards
Gururaja
-- 
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[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello,

2008/9/23 Hebbar <gururajakr@sanyo.co.in>:
> I use U-booot as The Primary Bootloader on arm926ej-s based Board.
>
> By Default U-boot supports few Primecell peripherals drivers like PL0x1
> UART.

Right, that's what I've found in the U-Boot sources. How come that
widely used interrupt controllers like PL19x are not supported by
default?

> I developed few others my self, like pl18x mmc, rtc, gpio.
>
> I recently sent a patch for RTC pl031.
Yes, I saw that patch. Are you planning to send patch for GPIO as well?

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Gururaja Hebbar K R]

Hi, 

> From: Roman Mashak [mailto:romez777 at gmail.com] 
> Subject: Re: [U-Boot] PrimeCell Peripherals
>
> Right, that's what I've found in the U-Boot sources. How come 
> that widely used interrupt controllers like PL19x are not 
> supported by default?

Thats because Most of the ARM based boards doesnt use Interrupts. Atleast as far as i have seen.
IIRC U-boot is a single process bootloader & hence Interrupts are not so much supported.
Is there any interrupt related drivers in U-boot for other platforms?

> > I recently sent a patch for RTC pl031.
> Yes, I saw that patch. Are you planning to send patch for 
> GPIO as well?

I havent done any Framework kind of a driver for GPIO. For me, it just works like a standalone & hence i cannot submit the same.
Later when i get time. I will prepare a GPIO Framework and submit for RFC in ML


Regards
Gururaja

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello,

2008/9/23 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:
> Thats because Most of the ARM based boards doesnt use Interrupts. Atleast as far as i have seen.
> IIRC U-boot is a single process bootloader & hence Interrupts are not so much supported.
> Is there any interrupt related drivers in U-boot for other platforms?

In U-Boot source tree there are number of drivers with interrupt
service routines running (for example,
$(U_BOOT)/drivers/net/bcm570x.c) as well as various interrupts related
macros (some of them not used thought), if this is what you mean.
Perhaps these definitions are for future ?

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

To add a bit to my previous message.

2008/9/23 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:
> Thats because Most of the ARM based boards doesnt use Interrupts. Atleast as far as i have seen.

As far as I understood from U-Boot's README, a standalone mode can and
may want to use interrupts -- so it'd reasonable to have interrupts
controllers support, isn't it? Correct me if I'm wrong, just trying to
understand the architecture of U-Boot more deeply.

> IIRC U-boot is a single process bootloader & hence Interrupts are not so much supported.
> Is there any interrupt related drivers in U-boot for other platforms?

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Gururaja Hebbar K R]

Hi, 

> In U-Boot source tree there are number of drivers with 
> interrupt service routines running (for example,
> $(U_BOOT)/drivers/net/bcm570x.c) as well as various 
> interrupts related macros (some of them not used thought), if 
> this is what you mean.
> Perhaps these definitions are for future ?

At $(U_BOOT)/drivers/net/bcm570x.c files header, it says 

 * Broadcom BCM570x Ethernet Driver for U-Boot.
 * Support 5701, 5702, 5703, and 5704. Single instance driver. 

--> Single Instance Driver. Does this mean it doesn't handle Interrupt. 
Sorry I cannot say more as I don't have any knowledge abt this

Also,

CONFIG_BCM570x is used in $(U_BOOT)/include/configs/BMW.h which is a MPC based Board. 

May be MPC uses interrupts for its operation inside U-Boot. 

Regards
Gururaja

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hi,

2008/9/23 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:

> At $(U_BOOT)/drivers/net/bcm570x.c files header, it says
>
>  * Broadcom BCM570x Ethernet Driver for U-Boot.
>  * Support 5701, 5702, 5703, and 5704. Single instance driver.
>
> --> Single Instance Driver. Does this mean it doesn't handle Interrupt.
> Sorry I cannot say more as I don't have any knowledge abt this
>
> Also,
>
> CONFIG_BCM570x is used in $(U_BOOT)/include/configs/BMW.h which is a MPC based Board.
>
> May be MPC uses interrupts for its operation inside U-Boot.

Probably you're right and interrupts related stuff is meanugful on PPC
platform; moreover README says about interrupts mainly in PPC or
PowerPC marked sections.

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Gururaja Hebbar K R]

HI, 

> From: Roman Mashak [mailto:romez777 at gmail.com] 
> Subject: Re: [U-Boot] PrimeCell Peripherals
>
> To add a bit to my previous message.
> 
> As far as I understood from U-Boot's README, a standalone 
> mode can and may want to use interrupts -- so it'd reasonable 
> to have interrupts controllers support, isn't it? Correct me 
> if I'm wrong, just trying to understand the architecture of 
> U-Boot more deeply.

U-boots readme is general  for all platforms.

Yes, U-boot ARM supports interrupt mode, but generally not used.
Also standalone can use interrupt mode if the u-boot it is running on is configured to support irq
i.e., CONFIG_USE_IRQ is defined.

Then the user has to also define a do_irq command to support the same

Kindly look at below file for do_irq function definitions & its usage.

uboot\cpu\arm720t\interrupts.c
uboot\cpu\arm920t\interrupts.c

i havent seen this function definitions for arm926ej-s except 

#ifndef CONFIG_USE_IRQ
void do_irq (struct pt_regs *pt_regs)
{
... 


Regards
Gururaja

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello,

2008/9/23 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:

[skip]
> Then the user has to also define a do_irq command to support the same
>
> Kindly look at below file for do_irq function definitions & its usage.
>
> uboot\cpu\arm720t\interrupts.c
> uboot\cpu\arm920t\interrupts.c
>
> i havent seen this function definitions for arm926ej-s except
>
> #ifndef CONFIG_USE_IRQ
> void do_irq (struct pt_regs *pt_regs)
> {
> ...

I'm a bit confused: 'do_irq' is defined in several files, including
CPU-specific (arm920t, 720t etc.) and ARM architecture library
($(U_BOOT)/lib_arm). So if we build for arm920t-based platform
(provided that CONFIG_USE_IRQ is defined), then which one will be
actually compiled in resulting image?

Thanks.

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Gururaja Hebbar K R]

Hi, 

> From: Roman Mashak [mailto:romez777 at gmail.com] 
> Subject: Re: [U-Boot] PrimeCell Peripherals
> 
> I'm a bit confused: 'do_irq' is defined in several files, 
> including CPU-specific (arm920t, 720t etc.) and ARM 
> architecture library ($(U_BOOT)/lib_arm). So if we build for 
> arm920t-based platform (provided that CONFIG_USE_IRQ is 
> defined), then which one will be actually compiled in resulting image?

Looking at uboot\cpu\arm920t\interrupts.c
a. If ARM920_IRQ_CALLBACK is defined (which is only used in s3c2410), function is called which points to s3c2410_irq()
b. if the platform is CONFIG_ARCH_INTEGRATOR, then it is assumed that it is 
for timer interrupt (which is not necessary be since timer interrupt is not enabled in integrator)


Looking at uboot\cpu\arm720t\interrupts.c
a. if CONFIG_S3C4510B is defined then platform specific interrupt handler is called ( IRQ_HANDLER[pending>>2].m_func() )
b. Noting for integrator
c here is the interesting part

Since LPC2292 uses the interrupt controller similar to VIC, It uses the VICVectAddr to get the respective function address & jumps to it.

So, a similar function i.e., do_irq is needed for arm926ej-s. Again inside it, a similar steps as in lpc2292 can be done to jump to respective function.

But i am not seeing anyone using this function yet. 


Regards
Gururaja

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello,

2008/9/24 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:
>> I'm a bit confused: 'do_irq' is defined in several files,
>> including CPU-specific (arm920t, 720t etc.) and ARM
>> architecture library ($(U_BOOT)/lib_arm). So if we build for
>> arm920t-based platform (provided that CONFIG_USE_IRQ is
>> defined), then which one will be actually compiled in resulting image?
[skip]

I must've confused you with the question. Let me try again: suppose we
build U-Boot for arm920t based target, in such a case, two files
defining 'do_irq' routine will be in compiled in --
$(UBOOT)/lib_arm/interrupts.c and $(UBOOT)/cpu/arm920t/interrupts.c.
Therefore I was wondering how it turns out that in the target image
one 'do_irq' function exists? Perhaps it's u-boot irrelevant question
and rather concern GNU toolchains behavior?

Thanks.

-- 
Roman Mashak

[U-Boot] PrimeCell Peripherals

[Gururaja Hebbar K R]

Hi, 

> From: Roman Mashak [mailto:romez777 at gmail.com] 
> Subject: Re: [U-Boot] PrimeCell Peripherals
> I must've confused you with the question. 
No u havent. Sorry to say that u havent checked the code properly

> suppose we build U-Boot for arm920t based target, in such a 
> case, two files defining 'do_irq' routine will be in compiled 
No it will not be.

in $(UBOOT)/lib_arm/interrupts.c 

#ifndef CONFIG_USE_IRQ				---> if not defined
void do_irq (struct pt_regs *pt_regs)
{
....
....

in $(UBOOT)/cpu/arm920t/interrupts.c

#ifdef CONFIG_USE_IRQ				---> if defined
#include <asm/proc-armv/ptrace.h>
void do_irq (struct pt_regs *pt_regs)
{
...
...

So both are mutual exclusive and finally only one will be compiled.

> Therefore I was wondering how it turns out that in the target 
> image one 'do_irq' function exists? Perhaps it's u-boot 
> irrelevant question and rather concern GNU toolchains behavior?

Its U-boot code style & GNU Toolchain compiler procedure in handling preprocessor statements.


Regards
Gururaja

[U-Boot] PrimeCell Peripherals

[Roman Mashak]

Hello,

2008/9/24 Gururaja Hebbar K R <gururajakr@sanyo.co.in>:

[skip]
> So both are mutual exclusive and finally only one will be compiled.

Exactly! Really I didn't spot that subtle difference -- #ifdef, #ifndef.
Thanks for pointing out.

-- 
Roman Mashak