Re: [PATCH master 1/3] RISC-V: cpu: request stack memory region

From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Antony Pavlov <antonynpavlov@gmail.com>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH master 1/3] RISC-V: cpu: request stack memory region
Date: Sat, 3 Apr 2021 09:09:15 +0200	[thread overview]
Message-ID: <2cd63d9c-903d-3670-6417-65d1fa324410@pengutronix.de> (raw)
In-Reply-To: <20210402111348.fcc6384084512f23588aad8f@gmail.com>

Hello Antony,

On 02.04.21 10:13, Antony Pavlov wrote:
>> This is strange. Could you print get_runtime_offset() at this location?
>> It should be zero, because relocate_to_current_adr() had previously run,
>> but it seems it's not for you? I don't see how compiler reordering could have
>> occurred given that we don't do LTO and relocate_to_current_adr is thus
>> a compiler barrier.

[ Naïve me thinking there are any guarantees from GCC for self-modifying code ]

> +    empty_slot_init(0, 0xffffffff);

That's tremendously useful. Thanks! I don't quite understand how it works
though. It registers a "fall-back" device for all of the 32-bit address
space?

> There are empty_slot read warnings on master:
> 
>     barebox$ qemu-system-riscv32 -nographic -M erizo -bios ./images/barebox-erizo-generic.img -serial stdio -monitor none -trace file=/dev/null 
>     >get_runtime_offset()=0x00000000
>     empty_slot: read from 0000000000022caf
>     empty_slot: read from 0000000000022cae
>     empty_slot: read from 0000000000022cb0
>     empty_slot: read from 0000000000022cb1
>     riscv-timer riscv-timer: running at 24000000 Hz
>     Switch to console [cs0]
> 
>     barebox 2021.03.0-00134-gc4a1684da9-dirty #1 Fri Apr 2 10:33:45 MSK 2021
> 
>     Board: generic Erizo SoC board
>     riscv-timer riscv-timer: running at 24000000 Hz
>     malloc space: 0x804ffd80 -> 0x805ffd7f (size 1 MiB)
> 
>     Hit any to stop autoboot:    1
>     boot: error 2
>     barebox:/ 
> 
> 
> There is no empty_slot warning with fef19e17f651^ barebox:
> 
>     barebox$ qemu-system-riscv32 -nographic -M erizo -bios ./images/barebox-erizo-generic.img -serial stdio -monitor none -trace file=/dev/null 
>     >RISC-V system with no 'timebase-frequency' in DTS
>     Switch to console [cs0]
> 
>     barebox 2021.03.0-00122-g6107208573 #1 Fri Apr 2 11:09:16 MSK 2021
> 
>     Board: generic Erizo SoC board
>     RISC-V system with no 'timebase-frequency' in DTS
>     malloc space: 0x802ffd80 -> 0x803ffd7f (size 1 MiB)
> 
>     Hit any to stop autoboot:    0
>     boot: error 2
>     barebox:/ 

Thanks. I identified two issues and CC'd you on a patch fixing them.
Breaking erizo has been a blessing to sort out this kind of bugs early :D

Cheers,
Ahmad

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