[RFC PATCH 1/1] arm: mach-k3: Enable icache on am625 to boot faster

[Francesco Dolcini]

On Thu, Nov 09, 2023 at 01:51:19PM -0500, Tom Rini wrote:
> On Thu, Nov 09, 2023 at 12:44:56PM -0600, Andrew Davis wrote:
> > On 11/9/23 11:37 AM, Nishanth Menon wrote:
> > > On 11:09-20231109, Joao Paulo Goncalves wrote:
> > > > Enable the am625 instruction cache on SPL and U-boot earlier for the A53
> > > > to execute code a bit faster. For normal boot flow, it was possible to
> > > > gain about 2 seconds on boot time.
> > > > 
> > > > Signed-off-by: Joao Paulo Goncalves <joao.goncalves at toradex.com>
> > > > ---
> > > > Hello all,
> > > > 
> > > > We are trying to optimize boot time on our AM62 devices and on TI community
> > > > forum [1] someone advised to enable ICACHE for am625. We enabled it, tested and got
> > > > around 2 seconds faster boot on storage media and about 5 seconds with DFU
> > > > for downloading images from A53 SPL. However, we don't know if this is the correct
> > > > solution and want more comments on this or why the ICACHE was not enabled by TI in
> > > > the first place.
> > > > 
> > > > [1] https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1217839/am625-boot-time-between-a53-spl-and-a53-u-boot
> > > > 
> > > > Regards,
> > > > Joao Paulo Goncalves
> > > > 
> > > >   arch/arm/mach-k3/am625_init.c | 3 +++
> > > >   1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/arch/arm/mach-k3/am625_init.c b/arch/arm/mach-k3/am625_init.c
> > > > index 8fa36f7b91..d665d07b0b 100644
> > > > --- a/arch/arm/mach-k3/am625_init.c
> > > > +++ b/arch/arm/mach-k3/am625_init.c
> > > > @@ -210,6 +210,9 @@ void board_init_f(ulong dummy)
> > > >   			panic("DRAM init failed: %d\n", ret);
> > > >   	}
> > > >   	spl_enable_dcache();
> > > > +
> > > > +	if (!IS_ENABLED(CONFIG_CPU_V7R) && !IS_ENABLED(CONFIG_SYS_ICACHE_OFF))
> > > > +		icache_enable();
> > > >   }
> > > >   u32 spl_mmc_boot_mode(struct mmc *mmc, const u32 boot_device)
> > > > -- 
> > > > 2.34.1
> > > 
> > > Just noticed that icache_enable was missed for all of k3 as well - I
> > > suspect this is a miss rather than anything consciously done. btw
...
> > We enable Icache in SPL for our CPU_V7R case inside setup_mpu_regions()(??)
> > We also enable Dcache in spl_enable_dcache(), maybe this should be
> > renamed spl_enable_cache() and it call enable_caches() which enables
> > both. Just be careful to invalidate the icache when enabling after
> > relocation.
> > 
> > This would be temporary, better solution would be to add it to the
> > SPL common board_init_r() to match the U-Boot one, that way all these
> > platforms wouldn't need to do it in their current inconsistent ways.
> 
> I will say that part of the reason we don't have a more high-level
> "enable all the caches in SPL on ARMv7" is that I never could figure out
> why on earth it locked up my am335x GP EVM, I believe. So yes, I'd be
> quite happy to see the mach-k3 case cleaned up and made generic to
> enable (and then disable/flush/enable in full). But we can't easily make
> it higher-level than that.

So the plan would be to enable the cache for SPL in mach-k3 and not just
for AM625, correct?

Andrew: is this something you could do or should we send a patch
ourselves? We can test only TI AM62.

Francesco