linux-kernel - Re: [PATCH] mdt: slram: use memremap() instead of ioremap()

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Message-ID: <befe7e20-da85-1ea5-d3ad-4698af0b7d05@caviumnetworks.com>
Date:   Tue, 17 Oct 2017 15:02:18 -0700
From:   David Daney <ddaney@...iumnetworks.com>
To:     Roy Franz <rfranz@...ium.com>, dwmw2@...radead.org,
        computersforpeace@...il.com, boris.brezillon@...e-electrons.com,
        marek.vasut@...il.com, richard@....at, cyrille.pitchen@...ev4u.fr
Cc:     roy.franz@...ium.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        ddaney@...ium.com
Subject: Re: [PATCH] mdt: slram: use memremap() instead of ioremap()

On 10/17/2017 01:56 PM, Roy Franz wrote:
> Convert slram to use memremap() to map the memory it uses to back an MTD
> device, as this is the proper interface for mapping memory. This change
> enables normal memory to be used to back an MTD device on arm64, as arm64
> prevents ioremap() being used on normal memory.
> 
> Signed-off-by: Roy Franz <roy.franz@...ium.com>

Thanks Roy.  I just tested on MIPS64 with no regressions, so:

Tested-by: David Daney <david.daney@...ium.com>


> ---
> Tested on arm64 simulation, using simulator to preload filesystem image into RAM,
> and also tested on x86_64 using video card memory.  This is useful for speeding
> up booting on (very slow) emulation environments by avoiding any processing of
> an initramfs.
> 
>   drivers/mtd/devices/slram.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/devices/slram.c b/drivers/mtd/devices/slram.c
> index 8087c36dc693..0ec85f316d24 100644
> --- a/drivers/mtd/devices/slram.c
> +++ b/drivers/mtd/devices/slram.c
> @@ -163,8 +163,9 @@ static int register_device(char *name, unsigned long start, unsigned long length
>   	}
>   
>   	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
> -				ioremap(start, length))) {
> -		E("slram: ioremap failed\n");
> +		memremap(start, length,
> +			 MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC))) {
> +		E("slram: memremap failed\n");
>   		return -EIO;
>   	}
>   	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
> @@ -186,7 +187,7 @@ static int register_device(char *name, unsigned long start, unsigned long length
>   
>   	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
>   		E("slram: Failed to register new device\n");
> -		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
> +		memunmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
>   		kfree((*curmtd)->mtdinfo->priv);
>   		kfree((*curmtd)->mtdinfo);
>   		return(-EAGAIN);
> @@ -206,7 +207,7 @@ static void unregister_devices(void)
>   	while (slram_mtdlist) {
>   		nextitem = slram_mtdlist->next;
>   		mtd_device_unregister(slram_mtdlist->mtdinfo);
> -		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
> +		memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
>   		kfree(slram_mtdlist->mtdinfo->priv);
>   		kfree(slram_mtdlist->mtdinfo);
>   		kfree(slram_mtdlist);
>