linux-kernel - Re: [PATCH 3/3] bus: fsl-mc: dpio: change CENA regs to be cacheable

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Date:   Fri, 21 Apr 2017 10:27:06 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Haiying Wang <Haiying.Wang@....com>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        linux-arm-kernel@...ts.infradead.org, roy.pledge@....com,
        stuyoder@...il.com
Subject: Re: [PATCH 3/3] bus: fsl-mc: dpio: change CENA regs to be cacheable

On Thu, Apr 20, 2017 at 03:34:18PM -0400, Haiying Wang wrote:
> plus non-shareable to meet the performance requirement.
> QMan's CENA region contains registers and structures that
> are 64byte in size and are inteneded to be accessed using a
> single 64 byte bus transaction, therefore this portal
> memory should be configured as cache-enabled. Also because
> the write allocate stash transcations of QBMan should be
> issued as cachable and non-coherent(non-sharable), we
> need to configure this region to be non-shareable.
> 
> Signed-off-by: Haiying Wang <Haiying.Wang@....com>
> ---
>  drivers/staging/fsl-mc/bus/dpio/dpio-driver.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/fsl-mc/bus/dpio/dpio-driver.c b/drivers/staging/fsl-mc/bus/dpio/dpio-driver.c
> index e36da20..97f909c 100644
> --- a/drivers/staging/fsl-mc/bus/dpio/dpio-driver.c
> +++ b/drivers/staging/fsl-mc/bus/dpio/dpio-driver.c
> @@ -168,10 +168,10 @@ static int dpaa2_dpio_probe(struct fsl_mc_device *dpio_dev)
>  	desc.cpu = next_cpu;
>  
>  	/*
> -	 * Set the CENA regs to be the cache inhibited area of the portal to
> -	 * avoid coherency issues if a user migrates to another core.
> +	 * Set the CENA regs to be the cache enalbed area of the portal to
> +	 * archieve the best performance.

Is migrating to another core no longer a concern?

As with my prior comments regarding the Non-Shareable mapping, I do not
thing this makes sense.

Thanks,
Mark.

>  	 */
> -	desc.regs_cena = ioremap_wc(dpio_dev->regions[1].start,
> +	desc.regs_cena = ioremap_cache_ns(dpio_dev->regions[1].start,
>  		resource_size(&dpio_dev->regions[1]));
>  	desc.regs_cinh = ioremap(dpio_dev->regions[1].start,
>  		resource_size(&dpio_dev->regions[1]));
> -- 
> 2.7.4
> 
> 
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> linux-arm-kernel@...ts.infradead.org
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