Hi Stephen,
> -----Original Message-----
> From: Stephen Warren <[email protected]>
> Sent: Tuesday, August 27, 2019 10:55 AM
> To: Tom Rini <[email protected]>
> Cc: [email protected]; [email protected]; Stephen Warren
> <[email protected]>; Vikas MANOCHA <[email protected]>
> Subject: [PATCH] board_f: fix noncached reservation calculation
>
> From: Stephen Warren <[email protected]>
>
> The current code in reserve_noncached() has two issues:
>
> 1) The first update of gd->start_addr_sp always rounds down to a section
> start. However, the equivalent calculation in cache.c:noncached_init()
> always first rounds up to a section start, then subtracts a section size.
> These two calculations differ if the initial value is already rounded to
> section
> alignment.
It shouldn't cause any issue, first one round down to section size. Second
one(cache.c: noncached_init()) rounds up, so needs section size subtraction.
>
> 2) The second update of gd->start_addr_sp subtracts exactly
> CONFIG_SYS_NONCACHED_MEMORY, whereas the equivalent calculation in
> cache.c:noncached_init() rounds the noncached size up to section alignment
> before subtracting it. The two calculations differ if the noncached region
> size
> is not a multiple of the MMU section size.
Never thought CONFIG_SYS_NON_CACACHED_MEMORY could be non-multiple of MMU
section size for basic MMU setup in u-boot. It has granularity of section size.
Is it the case with Jetson TX1 ?
>
> In practice, one/both of those issues causes a practical problem on Jetson
> TX1; U-Boot triggers a synchronous abort during initialization, likely due to
> overlapping use of some memory region.
>
> This change fixes both these issues by duplicating the exact calculations from
> noncached_init() into reserve_noncached().
>
> However, this fix assumes that gd->start_addr_sp on entry to
> reserve_noncached() exactly matches mem_malloc_start on entry to
> noncached_init(). I haven't traced the code to see whether it absolutely
> guarantees this in all (or indeed any!) cases. Consequently, I added some
> comments in the hope that this condition will continue to be true.
It is enforced it in the code, reserve_noncached is called from
reserve_malloc() after malloc area reservation.
>
> Fixes: 5f7adb5b1c02 ("board_f: reserve noncached space below malloc
> area")
> Cc: Vikas Manocha <[email protected]>
> Signed-off-by: Stephen Warren <[email protected]>
> ---
> arch/arm/lib/cache.c | 1 +
> common/board_f.c | 15 ++++++++++++---
> common/board_r.c | 4 ++++
> 3 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c index
> 449544d11cff..463d283cb768 100644
> --- a/arch/arm/lib/cache.c
> +++ b/arch/arm/lib/cache.c
> @@ -77,6 +77,7 @@ void noncached_init(void)
> phys_addr_t start, end;
> size_t size;
>
> + /* If this calculation changes, update board_f.c:reserve_noncached()
> +*/
> end = ALIGN(mem_malloc_start, MMU_SECTION_SIZE) -
> MMU_SECTION_SIZE;
> size = ALIGN(CONFIG_SYS_NONCACHED_MEMORY,
> MMU_SECTION_SIZE);
> start = end - size;
> diff --git a/common/board_f.c b/common/board_f.c index
> 6867abc8e679..591f18f391e2 100644
> --- a/common/board_f.c
> +++ b/common/board_f.c
> @@ -470,9 +470,18 @@ static int reserve_uboot(void) #ifdef
> CONFIG_SYS_NONCACHED_MEMORY static int reserve_noncached(void) {
> - /* round down to SECTION SIZE (typicaly 1MB) limit */
> - gd->start_addr_sp &= ~(MMU_SECTION_SIZE - 1);
> - gd->start_addr_sp -= CONFIG_SYS_NONCACHED_MEMORY;
> + /*
> + * The value of gd->start_addr_sp must match the value of
> malloc_start
> + * calculated in boatrd_f.c:initr_malloc(), which is passed to
> + * board_r.c:mem_malloc_init() and then used by
> + * cache.c:noncached_init()
> + *
> + * These calculations must match the code in
> cache.c:noncached_init()
> + */
> + gd->start_addr_sp = ALIGN(gd->start_addr_sp, MMU_SECTION_SIZE)
> -
> + MMU_SECTION_SIZE;
> + gd->start_addr_sp -= ALIGN(CONFIG_SYS_NONCACHED_MEMORY,
> + MMU_SECTION_SIZE);
> debug("Reserving %dM for noncached_alloc() at: %08lx\n",
> CONFIG_SYS_NONCACHED_MEMORY >> 20, gd->start_addr_sp);
>
> diff --git a/common/board_r.c b/common/board_r.c index
> b7f68bba4a7e..d6fb5047a265 100644
> --- a/common/board_r.c
> +++ b/common/board_r.c
> @@ -247,6 +247,10 @@ static int initr_malloc(void)
> gd->malloc_ptr / 1024);
> #endif
> /* The malloc area is immediately below the monitor copy in DRAM
> */
> + /*
> + * This value MUST match the value of gd->start_addr_sp in
> board_f.c:
> + * reserve_noncached().
> + */
minor cosmetic suggestion:
gd->start_addr_sp is moving pointer, difficult to comprehend sometimes here,
same is true for malloc
area also, how about merging two comments like:
/* The malloc area is immediately below the monitor copy in DRAM
followed by noncached
*/
Cheers,
Vikas
> malloc_start = gd->relocaddr - TOTAL_MALLOC_LEN;
> mem_malloc_init((ulong)map_sysmem(malloc_start,
> TOTAL_MALLOC_LEN),
> TOTAL_MALLOC_LEN);
> --
> 2.22.1
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