Fwd: Cache mappings and invalidate

[Joakim Tjernlund]

Hi all

Finally I got to enable burst read from flash, but my tests shows no performance gain.

There is no difference when I mont my JFFS2 FS or
if I do 'cp /dev/mtdblock4 /dev/null' or  'cp /dev/mtd4 /dev/null'. Even
if I remove the dma_cache_inv() call there is no performance gain.

It is almost like burst reads are disabled, but if I mess with the burst HW init sequence, 
I get a lot of errors, so I take it that burst reads are enabled.

I have a custom MPC860 board(4k icache, 4k dcache) running at 80 MHz
(bus is 40 Mhz),  128 MB Ram.

 Any Ideas? 

       Jocke

On Tuesday 13 November 2001 16:53, Joakim Tjernlund wrote:
> Hi again
>
> I did some changes since the first attempt  didn't work very well. I
> removed the changes in cfi_cmdset_0001.c and changed the copy_from()
> function to:
>
> void lumentis_copy_from(struct map_info *map, void *to, unsigned long from,
> ssize_t len) {
> #ifdef  USE_DCACHE
>        dma_cache_inv(map->map_priv_2 + from, len);
>        memcpy_fromio(to, (void *)(map->map_priv_2 + from), len);
> #else
>         memcpy_fromio(to, (void *)(map->map_priv_1 + from), len);
> #endif
> }
>
> This seems to work(no CRC errors so far) and has no visible impact on
> performance. When I get around to enable burst reads form my flash I hope
> to see a performance gain.
>
> Anybody care to comment on my experiment so far?
>
>           Jocke
>
> ----------  Forwarded Message  ----------
> Subject: Cache mappings and invalidate
> Date: Mon, 12 Nov 2001 14:14:14 +0200
> From: Joakim Tjernlund <Joakim.Tjernlund at lumentis.se>
> To: linux-mtd at lists.infradead.org
>
>
> Hi all
>
> I am trying to make copy_from use cahced memory by assignig
> map_priv_2 = (unsigned long)__ioremap(flash_addr, flash_size, 0);
> and then change copy_from routine to:
> +#ifndef NO_CACHE
> +       memcpy_fromio(to, (void *)(map->map_priv_2 + from), len);
> +#else
>         memcpy_fromio(to, (void *)(map->map_priv_1 + from), len);
> +#endif
>
> There are no cache invalidations in my map file, instead I have
> added invalidate_dcache_range() calls to
>  drivers/mtd/chips/cfi_cmdset_0001.c(see below) in do_write_oneword(),
>  do_write_buffer() and do_erase_oneblock(). Note that this is just a quick
>  hack to try out my theory. Does this look sane or should I use another
>  invalidate_dcache_range() and/or place the invalidate calls somewhere
> else?
>
> I am not using burst reads yet, that will come later once i have gotten the
>  cached mapping to work.
>
>        Joakim
>
>
>
> --- drivers/mtd/chips/cfi_cmdset_0001.c 2001/10/25 12:11:10     1.3
> +++ drivers/mtd/chips/cfi_cmdset_0001.c 2001/11/12 12:02:33
> @@ -502,6 +502,10 @@
>         cfi_udelay(chip->word_write_time);
>         spin_lock_bh(chip->mutex);
>
> +#ifndef NO_CACHE
> +       invalidate_dcache_range(map->map_priv_2 + adr, map->map_priv_2 +
> adr + 4); /* on a 32 bit bus */ +#endif
> +
>         timeo = jiffies + (HZ/2);
>         z = 0;
>         for (;;) {
> @@ -691,7 +695,7 @@
>         wbufsize = CFIDEV_INTERLEAVE << cfi->cfiq->MaxBufWriteSize;
>         adr += chip->start;
>         cmd_adr = adr & ~(wbufsize-1);
> -
> +
>         /* Let's determine this according to the interleave only once */
>         status_OK = CMD(0x80);
>
> @@ -790,6 +794,10 @@
>         cfi_udelay(chip->buffer_write_time);
>         spin_lock_bh(chip->mutex);
>
> +#ifndef NO_CACHE
> +       invalidate_dcache_range(map->map_priv_2 + adr, map->map_priv_2 +
> adr + len); +#endif
> +
>         timeo = jiffies + (HZ/2);
>         z = 0;
>         for (;;) {
> @@ -994,6 +1002,10 @@
>         spin_unlock_bh(chip->mutex);
>         schedule_timeout(HZ);
>         spin_lock_bh(chip->mutex);
> +
> +#ifndef NO_CACHE
> +       invalidate_dcache_range(map->map_priv_2 + adr, map->map_priv_2 +
> adr + 0x40000); /* 0x40000 is my erase size */
> +#endif
>
>         /* FIXME. Use a timer to check this, and return immediately. */
>         /* Once the state machine's known to be working I'll do that */
>
> -------------------------------------------------------