[U-Boot] SoCFPGA PL330 DMA driver and ECC scrubbing

[Jason Rush <jarush@gmail.com>]

On 7/3/2018 9:08 AM, Marek Vasut wrote:
> On 07/03/2018 03:58 PM, Jason Rush wrote:
>> On 6/29/2018 10:17 AM, Marek Vasut wrote:
>>> On 06/29/2018 05:06 PM, Jason Rush wrote:
>>>> On 6/29/2018 9:52 AM, Marek Vasut wrote:
>>>>> On 06/29/2018 04:44 PM, Jason Rush wrote:
>>>>>> On 6/29/2018 9:34 AM, Marek Vasut wrote:
>>>>>>> On 06/29/2018 04:31 PM, Jason Rush wrote:
>>>>>>>> Dinh,
>>>>>>> Hi,
>>>>>>>
>>>>>>>> A while ago, you posted the following patchset for SoCFPGA to add the PL330
>>>>>>>> DMA driver, and updated the SoCFPGA SDRAM init to write zeros to SDRAM to
>>>>>>>> initialize the ECC bits if ECC was enabled:
>>>>>>>>
>>>>>>>> https://lists.denx.de/pipermail/u-boot/2016-October/269643.html
>>>>>>>>
>>>>>>>> I know it's been a long time, so I'll summarize some of the conversation...
>>>>>>>>
>>>>>>>> At the time, you had a problem with the patchset causing the SPL to fail to
>>>>>>>> find the MMC.  You had tracked it down to an issue with the following commit
>>>>>>>> "a78cd8613204 ARM: Rework and correct barrier definitions".  You and Marek
>>>>>>>> discussed it a bit, but I don't think there was a real conclusion.  You
>>>>>>>> submitted a second version of the patchset asking for advice on debugging
>>>>>>>> the issue:
>>>>>>>>
>>>>>>>> https://lists.denx.de/pipermail/u-boot/2016-December/275822.html
>>>>>>>>
>>>>>>>> No real conversation came from the second patchset, and that was the end of
>>>>>>>> the patch.
>>>>>>>>
>>>>>>>> I was hoping we could revisit adding your patchset again. I am working on a
>>>>>>>> custom SoCFPGA board with a Cyclone V and ECC SDRAM. I rebased your patchset
>>>>>>>> against v2018.05 and it is working on my custom board (although I don't have
>>>>>>>> an MMC). I also tested it on a SoCKit booting from an MMC (I forced it to
>>>>>>>> scrub the SDRAM on the SoCKit, because it doesn't have ECC RAM), and the
>>>>>>>> SoCKit finds the MMC and boots.
>>>>>>>>
>>>>>>>> I don't have any suggestions on why it is working now on my board and not
>>>>>>>> back when you first submitted the patchset.  Maybe something else was fixed
>>>>>>>> in the MMC? I was hoping you and Marek could test this patch again on some
>>>>>>>> different SoCFPGA boards to see if you get the same results.
>>>>>>> Look at this patch
>>>>>>> http://git.denx.de/?p=u-boot/u-boot-socfpga.git;a=commit;h=9bb8a249b292d26f152c20e3641600b3d7b3924b
>>>>>>>
>>>>>>> You likely want similar approach, it's faster then the DMA and much simpler.
>>>>>>>
>>>>>> Thanks Marek.  I'll give it a try.  Would you be interested in a similar patch for the Gen 5?
>>>>> I don't have any Gen5 board which uses ECC, do you ?
>>>>> If so, yes, prepare a patch, it should be very similar.
>>>>>
>>>>> Make sure to measure how long it takes to scrub the memory and how much
>>>>> memory you have, I'd be interested in the numbers.
>>>>>
>>>> Looking at the master branch, it doesn't look like that code is ever being called?
>>>> The sdram_init_ecc_bits() function is called from the ddr_calibration_sequence function(),
>>>> but I can't find where ddr_calibration_sequence is called().
>>> git grep for it, it's called from somewhere in the arch/arm/mach-socfpga/
>>>
>>>> Either way, I can test it. I have a custom Cyclone V board with ECC, and the Intel Arria V SoC
>>>> Dev Kit I can test it on too which I think has ECC.
>>> Please do.
>>>
>> I implemented a similar memset approach for the gen 5 socfpga.  It's basically the same
>> code as in that patch; however, when I performed a single memset the processor would
>> reset for some reason.  I changed it to loop over calling memset with a size of 32MB over
>> the entire address the address, and that worked as opposed to doing a single memset on
>> the RAM.
> Can you do grep MEMSET .config in your U-Boot build dir ? The arch
> memset is implemented in assembler and doesn't trigger WDT , so if it
> takes too long, it could be that the WDT resets the platform.

Both CONFIG_USE_ARCH_MEMSET and CONFIG_SPL_USE_ARCH_MEMSET
are set in my .config, so it must be the WDT triggering as you suspect.

>> I started on a SoCKit because it was handy, I know it doesn't have ECC
> It doesn't by default.
>
>> , but I forced it to
>> initialize the RAM as a quick test.  It seems much slower than the DMA approach.  It
>> should be noted, I didn't implement any code to time the scrubbing, but rather just
>> roughly monitored the time to get a rough idea of how long it took.
>>
>> On the SoCKit, which has 1GB of RAM, the memset takes around 8 seconds to complete,
>> and the DMA takes under 2 seconds.
> Did you enable i/d cache in the SPL ? It's mandatory, otherwise it's
> slow.

I have calls to icache_enable() and dcache_enable() just as you do in
the Arria 10 sdram_init_ecc_bits() function.

I did double check that both these enable functions call the versions
of the functions in the ./arch/arm/lib/cache-cp15.c file that are
implemented in the SPL.  So I believe that both icache and dcache is
enabled.

I probably should have added a print of icache_status() and
dcache_status() to verify the caches are enabled.  I'll add that
tomorrow.

> Just be careful about the MMU tables placement, they are big and
> if you place them in RAM, make sure you don't overwrite them with the
> memset. The trick might be to memset the first 1 MiB of RAM, then put
> MMU tables at some offset therein (since 0x0 can be used for ARM
> vectors) and then turn on i/d cache and memset the rest.

That is essentially what I am doing I believe, with the exception that I
am only clearing the first 32KiB before initializing the MMU table (which
is what you did in the Arria 10 version).

I modeled my code almost identically to yours with the exception that
I loop over the memset calls 32MiB at a time. Here's the order of
operations I perform:

1. icache_enable()
2. memset the first 0x8000 bytes to zero
3. setup gd->arch.tlb_arch and gd->arch.tlb_size
4. dcache_enable()
5. loop over remaining memory, memsetting 32MiB at a time to zero
6. flush_dcache_all()
7. dcache_disable()

It looks like the call to dcache_enable is what sets up the MMU tables.
I suspect that's why you did a memset of the first 32KiB before enabling
the dcache on the Arria 10.  I think the MMU is initialized okay since the
SPL keeps executing, u-boot loads, and Linux boots after running the
above (maybe that's not a fair assumption).

>> Maybe I ported something wrong?  I used very similar code as the sdram_init_ecc_bits()
>> function, with the exception I looped over the second memset with a size of 32MB.  I
>> wasn't sure why the TLB address/size was being initialized, or if the values used on the
>> Arria 10 are even correct for the Cyclone 5,
> Because I needed to place MMU tables somewhere. The memory layout on
> CV/A10 are the same, RAM starts at 0, except the vectors can also be
> placed at 0, so the MMU tables should be at some offset.
>
>> but I used that part of the code as is from
>> the Arria 10 patch as well as enabling the icache and dcache just like the Arria 10 code.
>>
>> Any suggestions on what to look at?
>>
>> Jason
>>

Thank you for your help.

Regards,
Jason