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

Florian Fainelli
2024-05-03T18:56:48Z

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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

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