board_f: fix noncached reservation calculation

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.

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.

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.

Fixes: 5f7adb5b1c02 ("board_f: reserve noncached space below malloc area")
Cc: Vikas Manocha <vikas.manocha@st.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c
index 449544d..463d283 100644 (file)
--- 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 6867abc..591f18f 100644 (file)
--- 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 b7f68bb..d6fb504 100644 (file)
--- 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().
+        */
        malloc_start = gd->relocaddr - TOTAL_MALLOC_LEN;
        mem_malloc_init((ulong)map_sysmem(malloc_start, TOTAL_MALLOC_LEN),
                        TOTAL_MALLOC_LEN);