Re: [RFC PATCH 08/17] sunxi: introduce NCAT2 generation model

Andre Przywara
2023-05-17T08:56:57Z

On Wed, 17 May 2023 01:43:12 +0100
Andre Przywara <andre.przywara@arm.com> wrote:

+Maksim, as he was interested in the U-Boot series as well and had some
plans for SPI-NOR booting, IIUC.

Cheers,
Andre

> On Tue, 16 May 2023 17:53:38 -0600
> Sam Edwards <cfsworks@gmail.com> wrote:
>
> Hi Sam,
>
> > On 5/16/23 15:08, Andre Przywara wrote:
> > > This whole memory map is somewhat of a legacy. Apart from a few
> > > addresses for the SPL needs we shouldn't have those defines at all.
> > > Some symbols are needed because there are other macros using them,
> > > although these then are eventually unused.
> > > I have some patches to remove most of the symbols, and patch 14/17
> > > demonstrates some idea how to pin this down to what's really needed.
> > >
> > > For this particular case: this was copied from the H6 memory map, some
> > > addresses are just plain wrong for the D1 family. I will try to remove
> > > them as much as possible, leaving only the ones needed in.
> >
> > I see - the only "tangible" concern I had was the access to
> > prcm->res_cal_ctrl done in
> > arch/arm/mach-sunxi/clock_sun50i_h6.c:clock_init_safe
> >
> > This doesn't appear to upset the silicon but also doesn't seem necessary
> > either -- and with how tight of a memory footprint SPL has to fit into,
>
> What's the particular concern here? Compared to the A64 we are pretty
> cool: it's Thumb2 code and we are at around 27KB, at least with my
> toolchain. And I haven't tried, but I am pretty sure the BROM
> loads more than 32K, as it does on the H6 and H616 already. The U-Boot
> build system and the code already supports this - we rely on this for
> the H616 - so we can lift the limit anytime, if really needed.
>
> > I wanted to check whether this was just something undocumented or dead
> > code that needed to be removed. It sounds like it's mostly the latter.
>
> I haven't checked if the vendor boot0 does this. I am pretty sure there
> is a PRCM block, it's just regularly not mentioned in the manuals.
>
> > > So where did you see problems? If you would (wrongly) reference
> > > PortL somewhere in SPL GPIO code, it would use a wrong pointer, but at
> > > least the code would still compile fine, wouldn't it?
> >
> > The specific patch I had to apply (to arch/arm/mach-sunxi/board.c) was:
> > /* Update PIO power bias configuration by copy hardware
> > detected value */
> > val = readl(SUNXI_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_VAL);
> > writel(val, SUNXI_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_SEL);
> > - val = readl(SUNXI_R_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_VAL);
> > - writel(val, SUNXI_R_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_SEL);
> > + if (SUNXI_R_PIO_BASE) {
> > + val = readl(SUNXI_R_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_VAL);
> > + writel(val, SUNXI_R_PIO_BASE + SUN50I_H6_GPIO_POW_MOD_SEL);
> > + }
>
> Ah, I see, I indeed missed that. We seem to define all symbols anyway,
> so we can even lose the #ifdef and use proper if's here.
> Will incorporate that in the next drop.
>
> > With SUNXI_R_PIO_BASE being 0, this was actually attempting to write to
> > BROM. This might also be something that doesn't really upset the
> > silicon, though: my debug environment is a concolic emulator I quickly
> > hacked up to trace MMIO accesses, and it flagged the write to BROM as an
> > error. It was easier to patch the SPL than to have the emulator ignore
> > the error (and verify that the T113 was cool with it).
>
> Ah yeah, the Allwinner interconnect is pretty relaxed about those
> things: accesses to addresses with no device behind them are usually
> ignored (RAZ/WI), where other platform might throw an external abort.
> Writes to ROM areas are ignored as well.
>
> > Since this kind of extraneous/erroneous init code tends to remain
> > undetected when the symbols they need are dummied-out like this, I
> > figured I'd give a nudge in the direction of instead *removing* the
> > symbols where appropriate and fixing whatever breaks -- especially since
> > we really need to be thrifty about SPL size. But that might also be
> > something that happens in a later cleanup pass when the patchset is
> > being prepared for upstream inclusion. :)
> >
> > > P.S. Could you try the github post? Then compiled and booted fine for
> > > me, and includes the DRAM code as well now:
> > > https://github.com/apritzel/u-boot/commits/t113s-mq-r-WIP
> >
> > Ooh, more up-to-date code, thanks for the link! I'll switch to using
> > this instead going forward. My pulls from that branch might be
> > relatively infrequent
>
> Don't worry, I won't push to this anymore.
>
> > since I'm also working on some patches for better
> > Clang compatibility concurrent with the efforts here. Is this email
> > thread a good venue for feedback against that branch or would you prefer
> > that I use GitHub issues instead?
>
> Please use this thread here, if you find something still wrong in the
> branch. I just pushed it to github since someone asked for a fixed
> and complete version, and I didn't have time to prepare a proper post
> again.
>
> I will hopefully post a proper version for upstreaming in the next days.
>
>
> > Warm regards,
> > Sam
> >
> > P.S. My target is the BMC on the Turing Pi 2 board.
>
> Ah, interesting, didn't know that this is now a BMC - for a
> SoC from Allwinner's arch nemesis Rockchip ;-)
>
> > They have the same
> > SoC and (apparently) UART console configuration, but the differences end
> > there: in particular, my target supports boot from either/both
> > microSD+SPI-NAND. I might have to start pushing for room for SPI drivers
> > in the SPL soon. :)
>
> We already have SPI(-NOR) booting support, check
> arch/arm/mach-sunxi/spl_spi_sunxi.c. This code is very small, and just
> needs to be updated to cover the D1/T113 SPI controller, which is
> slightly different. See
> https://lore.kernel.org/linux-arm-kernel/20230507150345.1971083-1-bigunclemax@gmail.com/
> for the Linux SPI bits.
> Regarding SPI-*NAND*: there is
> https://patchwork.ozlabs.org/user/todo/uboot/?series=322733
> which is supposed to allow loading U-Boot proper from SPI-NAND. I
> haven't tested it yet, and wasn't overly happy with the refactoring, but
> would appreciate any kind of review or test.
>
> Cheers,
> Andre