Re: 5.2-rc1 boot on Unleashed

From: Troy Benjegerdes <troy.benjegerdes@sifive.com>
To: Anup Patel <anup@brainfault.org>
Cc: "Palmer Dabbelt" <palmer@sifive.com>,
	"Björn Töpel" <bjorn.topel@gmail.com>,
	"Anup Patel" <anup.patel@wdc.com>,
	"Atish Patra" <atish.patra@wdc.com>,
	"Lukas Auer" <lukas.auer@aisec.fraunhofer.de>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"Bin Meng" <bmeng.cn@gmail.com>
Subject: Re: 5.2-rc1 boot on Unleashed
Date: Sat, 25 May 2019 09:16:26 -0500	[thread overview]
Message-ID: <4572851B-EF46-45A1-A806-663894673EF9@sifive.com> (raw)
In-Reply-To: <CAAhSdy0R6UgxhgrU9NZegmoigjqZmx6RwoGngPdmzrzaUUxpTA@mail.gmail.com>

> On May 25, 2019, at 3:06 AM, Anup Patel <anup@brainfault.org> wrote:
> 
> Hi Troy,
> 
> On Thu, May 23, 2019 at 3:45 AM Troy Benjegerdes
> <troy.benjegerdes@sifive.com> wrote:
>> 
>> 
>>> On May 22, 2019, at 3:43 PM, Paul Walmsley <paul.walmsley@sifive.com> wrote:
>>> 
>>> + Anup, Troy
>>> 
>>> On Wed, 22 May 2019, Atish Patra wrote:
>>> 
>>>> On 5/22/19 9:42 AM, Paul Walmsley wrote:
>>>>> Am checking on this now and hope to have some conclusion on it this week.
>>>> 
>>>> Thanks. Any chance you can take a look at the U-Boot clock driver to patch it
>>>> as per the DT changes ?
>>> 
>>> I probably won't have the chance to get to it for a while.  Looks like
>>> Anup was the one who posted the clock driver to U-Boot - can he take a
>>> look at it?
>>> 
>>> We've also asked Troy to look at upstream U-boot related issues, but
>>> I'm unsure when patches will start flowing upstream.
>>> 
>>> 
>>> - Paul
>> 
>> Once I figure out why I’m getting TX timeouts on the macb driver and have something working I can start upstreaming the u-boot patches.
>> 
>> For now, the work-in-progress is at https://github.com/sifive/u-boot/tree/sandbox
> 
> Based on your commits in above GitRepo, it seems you are trying entire
> U-Boot in M-mode.
> 
> Current boot-flow of S-mode U-Boot is:
> ZSBL (M-mode) -> FSBL (M-mode) -> OpenSBI/BBL (M-mode) -> U-Boot (S-mode)
> 
> The U-Boot SPL can perfectly replace SiFive FSBL to have following
> boot-flow:
> ZSBL (M-mode) -> U-Boot SPL (M-mode) -> OpenSBI/BBL (M-mode) -> U-Boot (S-mode)
> 
> Can you explain advantages of using full U-Boot M-mode to replace
> FSBL as compared to U-Boot SPL M-mode replacing FSBL ?
> 
> Regards,
> Anup

The current flow in Freedom-u-sdk (with https://github.com/sifive/HiFive_U-Boot) is this:
ZSBL (M-mode) -> U-Boot (M-mode) -> BBL -> Linux kernel

The major driver for full U-Boot M-mode is automated regression testing and being able
to load the SBI interface (BBL or OpenSBI) and linux kernel via TFTP.

I do agree U-Boot SPL is a very good idea, I have been working on replicating the
functionality of the old HiFive U-boot first and then once that works I think it will be a
lot easier to work out the SPL option.

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