Re: [PATCH 5/6] mips: bmips: enable RAC on BMIPS4350

Daniel González Cabanelas
2024-05-03T21:11:24Z

Hi Florian.
Bits 0 and 1 are already enabled by the bootloader, so no need to
write 0xF. I checked it on some devices with BCM6328, 6358, 6368 SoCs.

Example, without the patch, reading the RAC Configuration Register 0 and 1:

- BCM6368 booting from TP0:
root@OpenWrt:/# devmem 0xff400000
0x02A07015
root@OpenWrt:/# devmem 0xff400008
0x0000000F

- BCM6368 booting from TP1:
root@OpenWrt:/# devmem 0xff400000
0x02A0701F
root@OpenWrt:/# devmem 0xff400008
0x00000005
root@OpenWrt:/#

Regards.
Daniel

El vie, 3 may 2024 a las 20:56, Florian Fainelli
(<florian.fainelli@broadcom.com>) escribió:
>
> On 5/3/24 06:54, Christian Marangi wrote:
> > From: Daniel González Cabanelas <dgcbueu@gmail.com>
> >
> > The data RAC is left disabled by the bootloader in some SoCs, at least in
> > the core it boots from.
> > Enabling this feature increases the performance up to +30% depending on the
> > task.
> >
> > Signed-off-by: Daniel González Cabanelas <dgcbueu@gmail.com>
> > Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
> > [ rework code and reduce code duplication ]
> > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> > ---
> > arch/mips/kernel/smp-bmips.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
> > index 6048c471b5ee..7bde6bbaa41f 100644
> > --- a/arch/mips/kernel/smp-bmips.c
> > +++ b/arch/mips/kernel/smp-bmips.c
> > @@ -617,6 +617,18 @@ void bmips_cpu_setup(void)
> > __raw_readl(bmips_cbr_addr + BMIPS_RAC_ADDRESS_RANGE);
> > break;
> >
> > + case CPU_BMIPS4350:
> > + u32 rac_addr = BMIPS_RAC_CONFIG_1;
> > +
> > + if (!(read_c0_brcm_cmt_local() & (1 << 31)))
> > + rac_addr = BMIPS_RAC_CONFIG;
> > +
> > + /* Enable data RAC */
> > + cfg = __raw_readl(bmips_cbr_addr + rac_addr);
> > + __raw_writel(cfg | 0xa, bmips_cbr_addr + rac_addr);
>
> This enables data pre-fetching (bit 3) and data-caching (bit 1), have
> you tried with 0xF to see if this provides any additional speed-up?
>
> Looks correct to me otherwise, I wonder if a flush would be in order
> right after enabling, though I did not see any specific instructions
> towards that part in the programming notes.
>
> > + __raw_readl(bmips_cbr_addr + rac_addr);
> > + break;
> > +
> > case CPU_BMIPS4380:
> > /* CBG workaround for early BMIPS4380 CPUs */
> > switch (read_c0_prid()) {
>
> --
> Florian
>