linux-kernel - Re: [PATCH] MIPS: c-r4k: Invalidate BMIPS5000 ZSCM prefetch lines

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Date:   Thu, 6 Feb 2020 19:55:39 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Kamal Dasu <kdasu.kdev@...il.com>, linux-kernel@...r.kernel.org
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        James Hogan <jhogan@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com, linux-mips@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH] MIPS: c-r4k: Invalidate BMIPS5000 ZSCM prefetch lines



On 2/6/2020 11:30 AM, Kamal Dasu wrote:
> Zephyr secondary cache is 256KB, 128B lines. 32B sectors. A secondary cache
> line can contain two instruction cache lines (64B), or four data cache
> lines (32B). Hardware prefetch Cache detects stream access, and prefetches
> ahead of processor access. Add support to inavalidate BMIPS5000 cpu zephyr

s/inavalidate/invalidate/

> secondary cache module (ZSCM) on DMA from device so that data returned is
> coherent during DMA read operations.

Just a few nits, see below, with those addressed:

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>

> 
> Signed-off-by: Kamal Dasu <kdasu.kdev@...il.com>
> ---
>  arch/mips/mm/c-r4k.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
> index 5f3d0103b95d..2d8892ba68ab 100644
> --- a/arch/mips/mm/c-r4k.c
> +++ b/arch/mips/mm/c-r4k.c
> @@ -901,6 +901,35 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size)
>  	__sync();
>  }
>  
> +static void prefetch_cache_inv(unsigned long addr, unsigned long size)
> +{
> +	unsigned int linesz = cpu_scache_line_size();
> +	unsigned long addr0 = addr, addr1;
> +	int cpu_type = current_cpu_type();
> +
> +	if (cpu_type == CPU_BMIPS5000) {

I would re-organize this and move this out of the prefetch_cache_inv()
such that platforms which do not require that operation can have it
optimized out, see below:

> +		/* invalidate zephyr secondary cache module prefetch lines */
> +		addr0 &= ~(linesz - 1);
> +		addr1 = (addr0 + size - 1) & ~(linesz - 1);
> +
> +		protected_writeback_scache_line(addr0);
> +		if (likely(addr1 != addr0))
> +			protected_writeback_scache_line(addr1);
> +		else
> +			return;
> +
> +		addr0 += linesz;
> +		if (likely(addr1 != addr0))
> +			protected_writeback_scache_line(addr0);
> +		else
> +			return;
> +
> +		addr1 -= linesz;
> +		if (likely(addr1 > addr0))
> +			protected_writeback_scache_line(addr0);
> +	}
> +}
> +
>  static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
>  {
>  	/* Catch bad driver code */
> @@ -908,6 +937,7 @@ static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
>  		return;
>  
>  	preempt_disable();

	if (current_cpu_type() == CPU_BMIPS5000)
		prefetch_cache_inv(addr, size);

> +	prefetch_cache_inv(addr, size);
>  	if (cpu_has_inclusive_pcaches) {
>  		if (size >= scache_size) {
>  			if (current_cpu_type() != CPU_LOONGSON64)
> 

-- 
Florian