[U-Boot] [PATCH] arm: socfpga: make debug uart work on socfpga_gen5

[Marek Vasut]

On 1/8/19 7:41 AM, Simon Goldschmidt wrote:
> On Mon, Jan 7, 2019 at 11:58 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 1/7/19 10:01 PM, Simon Goldschmidt wrote:
>>> Am 07.01.2019 um 21:47 schrieb Marek Vasut:
>>>> On 1/7/19 9:33 PM, Simon Goldschmidt wrote:
>>>>> Am 07.01.2019 um 21:25 schrieb Marek Vasut:
>>>>>> On 1/7/19 9:24 PM, Simon Goldschmidt wrote:
>>>>>>> Am 07.01.2019 um 21:19 schrieb Marek Vasut:
>>>>>>>> On 1/7/19 8:36 PM, Simon Goldschmidt wrote:
>>>>>>>>> When debug UART is enabled on socfpga_gen5, the debug uart driver
>>>>>>>>> hangs
>>>>>>>>> in an endless loop because 'socfpga_bridges_reset' calls printf
>>>>>>>>> before
>>>>>>>>> the debug UART is initialized.
>>>>>>>>>
>>>>>>>>> After the generic fix for this in the UART driver did not work
>>>>>>>>> due to
>>>>>>>>> portability issues, let's just drop this printf statement when
>>>>>>>>> called
>>>>>>>>> from SPL with debug UART enabled.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
>>>>>>>>
>>>>>>>> Can we have an un-portable fix which at least works on SoCFPGA ? :)
>>>>>>>
>>>>>>> This one worked on socfpga but broke rockchip:
>>>>>>>
>>>>>>> https://patchwork.ozlabs.org/patch/992553/
>>>>>>>
>>>>>>> However, the message below wasn't shown either with that patch
>>>>>>> applied.
>>>>>>> The code just runs too early to enable the UART.
>>>>>>>
>>>>>>> Do you want to keep the message (although I failed to see in which
>>>>>>> situation it can be printed) or do you just dislike the #ifdef thing?
>>>>>>
>>>>>> I'd like to keep the error message if possible. Is it possible ?
>>>>>
>>>>> I have *never* seen this message yet. I have failed to produce a
>>>>> situation where it is shown.
>>>>
>>>> I believe that.
>>>>
>>>>> This function ('socfpga_bridges_reset') is called 5 times throughout the
>>>>> code, but only *one* single time with 'reset=0' as argument (only with
>>>>> 0, the code in question is executed). And this is in SPL before
>>>>> initializing the console and even before the debug UART can be
>>>>> initialized.
>>>>>
>>>>> As I could see, the printf *is* executed on every boot (I saw the code
>>>>> hanging when enabling debug UART). However, when not booting from FPGA,
>>>>> it is just normal that the FPGA is not ready when running SPL. Why do
>>>>> you want an error message here anyway?
>>>>
>>>> I was under the impression this is an error message, but it might not be
>>>> so ? Maybe the wording is incorrect ?
>>>
>>> Now that I re-read it, "aborting" is incorrect, yes.
>>>
>>> So how should we proceed? This is an error message that can never be
>>> shown (like the code is now) but breaks debug UART.
>>>
>>> I'd say we can drop it altogether. It might only be interesint if (in
>>> the future) that code would get called from somewhere else (i.e. later,
>>> after console initialization).
>>>
>>> Re-reading spl_gen5.c, there are some 'debug' calls before the debug
>>> uart is initialized which probably would need to be removed as well, but
>>> that's a different story...
>>
>> How come those don't hang the system then ?
> 
> I just haven't enabled debug output in spl_gen5.c, yet. I guess they would hang
> the system when enabling them.
> 
> While it would be easy to remove these debug statements, to be future-proof
> it would of course make sense to make the debug UART robust against this.
> 
> But given the problems with Rockchip ns16550, we would need a dedicated
> debug UART for socfpga to solve this. And that would probably mean code
> duplication.

What is the problem with Rockchip ? I don't want various SoCs blocking
others.

-- 
Best regards,
Marek Vasut