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

[Ard Biesheuvel]

On 17 October 2017 at 21:56, Roy Franz <rfranz@xxxxxxxxxx> 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@xxxxxxxxxx>

Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

> ---
> 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);
> --
> 2.11.0
>
>
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