On Jun 2, 2019, at 9:22 PM, Rick Chen rickchen36@gmail.com wrote:
Hi Troy
From: Troy Benjegerdes [mailto:troy.benjegerdes@sifive.com] Sent: Saturday, June 01, 2019 12:24 AM To: Auer, Lukas Cc: Rick Jian-Zhi Chen(陳建志); bmeng.cn@gmail.com; palmer@sifive.com Subject: Re: Hart lottery and CONFIG_XIP
On May 31, 2019, at 9:13 AM, Auer, Lukas lukas.auer@aisec.fraunhofer.de
wrote:
Hi Troy,
On Fri, 2019-05-31 at 08:18 -0500, Troy Benjegerdes wrote:
Wouldn't the following line in head.S fail when running from flash (although maybe not in a way that prevents booting)
/* save the boot hart id to global_data */ SREG tp, GD_BOOT_HART(gp)Shouldn’t this be protected by CONFIG_XIP?
The boot hart ID is stored in global data, which is allocated from the stack (in board_init_f_alloc_reserve() ). It is therefore writable and won't cause any issues when running from flash.
Sorry about the confusion, I was reading it wrong earlier.
I’m hoping to have a couple of patches ready later today to change the CONFIG_XIP patch to ‘CONFIG_HART_LOTTERY’ since it is also useful to remove the potential indeterminism of which hart wins the lottery when doing board bringup and debugging.
I am OK with that. Actually my preliminary patch about [PATCH 0/4] AE350 support SMP boot from flash did as your wish.
You can refer it : [PATCH 1/4] riscv: hart_lottery and available harts feature can be seletable https://www.mail-archive.com/u-boot@lists.denx.de/msg323419.html
Rick
To follow up on https://www.mail-archive.com/u-boot@lists.denx.de/msg323526.html
It is confusing and misleading to mix CONFIG_XIP and CONFIG_HART_LOTTERY.
From an system testing and validation point of view, I would find it much better (especially at very early boot stages, where U-boot might be the first non-ROM code running) to have a deterministic process to determine what core runs U-boot. This necessarily seems as it will require a CONFIG_BOOT_HART option, as we are not in a position to parse a device tree in head.S