linux-kernel - Re: [PATCH] staging: tidspbridge

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Date:	Wed, 5 Jan 2011 12:46:05 -0600
From:	"Ramirez Luna, Omar" <omar.ramirez@...com>
To:	Fernando Guzman Lugo <fernando.lugo@...com>
Cc:	gregkh@...e.de, rene.sapiens@...com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	Felipe Contreras <felipe.contreras@...ia.com>
Subject: Re: [PATCH] staging: tidspbridge - configure full L1 MMU range

Hi,

On Wed, Jan 5, 2011 at 12:20 AM, Fernando Guzman Lugo
<fernando.lugo@...com> wrote:
> Otherwise a virtual address beyond of the L1 size is used,
> the MMU hardware will look into a memory that does not belong to
> L1 translation tables. IOW; the MMU would allow to access any
> memory, configured or not.
>

How about:

IVA MMU can manage up to 4GB of address space through its page tables,
given that it's L1 is divided into 1MB sections it requires at least
16KB for its table which represents 4096 entries of 32 bits each.

Previously, only 1GB was being handled by setting the page table size
to 4KB, any virtual address beyond of the L1 size used, would fall
into memory that does not belong to L1 translation tables, leading to
unpredictable results.

So, set the L1 table size to cover the entire MMU range (4GB) whether
is meant to be used or not.

> Reported-by: Felipe Contreras <felipe.contreras@...ia.com>
> Signed-off-by: Fernando Guzman Lugo <fernando.lugo@...com>
> Signed-off-by: Felipe Contreras <felipe.contreras@...ia.com>
> ---
>  drivers/staging/tidspbridge/core/tiomap3430.c |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/tidspbridge/core/tiomap3430.c b/drivers/staging/tidspbridge/core/tiomap3430.c
> index 1be081f..ec96d1e 100644
> --- a/drivers/staging/tidspbridge/core/tiomap3430.c
> +++ b/drivers/staging/tidspbridge/core/tiomap3430.c
> @@ -70,6 +70,7 @@
>  #define MMU_LARGE_PAGE_MASK      0xFFFF0000
>  #define MMU_SMALL_PAGE_MASK      0xFFFFF000
>  #define OMAP3_IVA2_BOOTADDR_MASK 0xFFFFFC00
> +#define MMU_L1_SIZE              0x4000
>  #define PAGES_II_LVL_TABLE   512
>  #define PHYS_TO_PAGE(phys)      pfn_to_page((phys) >> PAGE_SHIFT)
>
> @@ -786,10 +787,7 @@ static int bridge_dev_create(struct bridge_dev_context
>
>        pt_attrs = kzalloc(sizeof(struct pg_table_attrs), GFP_KERNEL);
>        if (pt_attrs != NULL) {
> -               /* Assuming that we use only DSP's memory map
> -                * until 0x4000:0000 , we would need only 1024
> -                * L1 enties i.e L1 size = 4K */
> -               pt_attrs->l1_size = 0x1000;
> +               pt_attrs->l1_size = MMU_L1_SIZE;

How about using SZ_16K instead, struct member name already specifies
it is L1 size, is the new define needed?

Regards,

Omar
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