Re: [PATCH] Add new command fs2bridge for socfpga

[Mabcded Babcde <thepusherpushes@gmail.com>]

2017-08-01 11:13 GMT+02:00 Steffen Trumtrar <s.trumtrar@pengutronix.de>:
>
> Hi!
>
> Andrey Smirnov <andrew.smirnov@gmail.com> writes:
>
>> On Sun, Jul 30, 2017 at 2:17 PM, Mabcded Babcde
>> <thepusherpushes@gmail.com> wrote:
>>> 2017-07-28 15:42 GMT+02:00 Andrey Smirnov <andrew.smirnov@gmail.com>:
>>>> On Fri, Jul 28, 2017 at 6:24 AM, Mabcded Babcde
>>>> <thepusherpushes@gmail.com> wrote:
>>>>> 2017-07-27 20:49 GMT+02:00 Andrey Smirnov <andrew.smirnov@gmail.com>:
>>>>>> On Thu, Jul 27, 2017 at 9:20 AM, Mabcded Babcde
>>>>>> <thepusherpushes@gmail.com> wrote:
>>>>>>> Hi,
>>>>>>> this patch adds a new command to barebox. It is used to enable or
>>>>>>> disable the fpga-to-sdram bridges on socfpgas. The patch is based on a
>>>>>>> manual from altera
>>>>>>> (https://www.altera.com/support/support-resources/knowledge-base/embedded/2016/how-and-when-can-i-enable-the-fpga2sdram-bridge-on-cyclone-v-soc.html)
>>>>>>> and a implementation for u-boot
>>>>>>> (https://github.com/rogerq/u-boot/blob/master/arch/arm/mach-socfpga/misc.c).
>>>>>>> The fpga2sdram fpga configuration can only be set when the SDRAM
>>>>>>> interface is idle. So it is necessary to use the on-chip ram.
>>>>>>
>>>>>> And by "on-chip ram" you mean i-cache and not SRAM block used by first
>>>>>> stage bootloader, correct? I am just a bit confused by the wording.
>>>>>>
>>>>>
>>>>> Sorry, my fault. I meant i-cache.
>>>>>
>>>>>>> To bring all fpga2sdram bridges out of reset it is necessary to write 0x3FFF to
>>>>>>> the register. Only the fpga2sdram bridges are enabled or disabled but
>>>>>>> no other bridges like the axi bridges.
>>>>>>
>>>>>> Linux kernel already has:
>>>>>>
>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/fpga/altera-fpga2sdram-bridge.txt?h=v4.13-rc2
>>>>>>
>>>>>> so, IMHO, it would be better to implement  a compatible driver and, if
>>>>>> ability to change the value at run-time is needed, add "enable"
>>>>>> property to it rather than introducing a separate command.
>>>>>>
>>>>>
>>>>> But how can I ensure that the SDRAM is idle? I quote Altera:
>>>>> "First time enabling of the FPGA2SDRAM bridge within Linux is not
>>>>> supported as the SDRAM subsystem cannot be easily put into a
>>>>> guaranteed idle state."
>>>>>
>>>>
>>>> I feel like we are talking about different things. What I am trying to
>>>> say that instead of adding this functionality to Barebox as a
>>>> standalone command, it would be better to add it _to Barebox_ as a
>>>> driver that claims compatibility with "altr,socfpga-fpga2sdram-bridge"
>>>> and implements all of the necessary logic there. It would be the same
>>>> code running in the boot-loader but triggered to executed via
>>>> different means, so it should literally be the same in terms of SDRAM
>>>> access quiescence. A somewhat relative example of that approach would
>>>> be "drivers/firmware/socfpga.c".
>>>
>>> Ok, I hardcoded my code from the command to drivers/firmware/socfpga.c
>>> for testing purposes. That didn't seem to work.
>>
>> I'd double check that CONFIG_FIRMWARE and
>> CONFIG_FIRMWARE_ALTERA_SOCFPGA are set to "y".
>>
>>> However how would I
>>> enable or disable the bridge? With a parameter? Where can I add it and
>>> change it?
>>>
>>>>
>>
>> The driver in firmware/socfpga.c should create a "fpga0" device, after
>> which, you cat set that device's variables/attributes by simply doing:
>>
>> fpga0.variable_name = value
>>
>> and get them via
>>
>> echo ${fpga0.variable_name}
>>
>
> The right approach should be adding a proper bridge driver like in the
> kernel. Then in the fpgamgr_program_finish enable all registered
> bridges. And set the APPFLYCFG bit in the bridge driver.
> Or do I miss something?
>
> The cacheline magic seems rather fragile and therefore just running a
> function (with almost the same assembler code) from OCRAM seems to be the
> more robust option.
>
> As a matter of fact, I already have the bridge drivers ported to
> barebox. I can post the series as an RFC as I haven't tested it since I
> rebased it to v2017.07.0.

I built Barebox successfully with your drivers, but the fpga-bridge
wasn't enabled. And where is the OCRAM part in your driver?

>
>
> Regards,
> Steffen
>
> --
> Pengutronix e.K.                           | Steffen Trumtrar            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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