[PATCH v2 2/2] ARM: mmu_32: fix setting up zero page when it is in SDRAM

[Sascha Hauer <s.hauer@pengutronix.de>]

We used to skip setting the zero page to faulting when SDRAM starts
at 0x0. As bootm code now explicitly sets the zero page accessible
before copying ATAGs there this should no longer be necessary, so
unconditionally set the zero page to faulting during MMU startup.
This also moves the zero page setup after the point the SDRAM has
been mapped cachable, because otherwise the zero page setup would
be overwritten.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/cpu/mmu_32.c | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/arch/arm/cpu/mmu_32.c b/arch/arm/cpu/mmu_32.c
index c4e5a3bb0a..fdbc0293a3 100644
--- a/arch/arm/cpu/mmu_32.c
+++ b/arch/arm/cpu/mmu_32.c
@@ -459,23 +459,6 @@ static int set_vector_table(unsigned long adr)
 	return -EINVAL;
 }
 
-static void create_zero_page(void)
-{
-	struct resource *zero_sdram;
-
-	zero_sdram = request_sdram_region("zero page", 0x0, PAGE_SIZE);
-	if (zero_sdram) {
-		/*
-		 * Here we would need to set the second level page table
-		 * entry to faulting. This is not yet implemented.
-		 */
-		pr_debug("zero page is in SDRAM area, currently not supported\n");
-	} else {
-		zero_page_faulting();
-		pr_debug("Created zero page\n");
-	}
-}
-
 /*
  * Map vectors and zero page
  */
@@ -487,7 +470,6 @@ static void vectors_init(void)
 	 */
 	if (!set_vector_table((unsigned long)__exceptions_start)) {
 		arm_fixup_vectors();
-		create_zero_page();
 		return;
 	}
 
@@ -495,7 +477,6 @@ static void vectors_init(void)
 	 * Next try high vectors at 0xffff0000.
 	 */
 	if (!set_vector_table(ARM_HIGH_VECTORS)) {
-		create_zero_page();
 		create_vector_table(ARM_HIGH_VECTORS);
 		return;
 	}
@@ -552,6 +533,13 @@ void __mmu_init(bool mmu_on)
 
 		remap_range((void *)pos, bank->start + bank->size - pos, MAP_CACHED);
 	}
+
+	/*
+	 * In case the zero page is in SDRAM request it to prevent others
+	 * from using it
+	 */
+	request_sdram_region("zero page", 0x0, PAGE_SIZE);
+	zero_page_faulting();
 }
 
 /*
-- 
2.39.2