ARM: shmobile: No R-Car Gen2 CMA reservation when HIGHMEM=n

From: Magnus Damm <[email protected]>

Allow R-Car Gen2 platforms to boot with CMA enabled and HIGHMEM disabled. This patch adds code to check if the R-Car Gen2 specific memory reservation window is included in the kernel memory range or not. When HIGHMEM is disabled the R-Car Gen2 reservation area is outside the kernel memory range and in such case the memory reservation is simply skipped over.

Without this patch the kernel boot hangs when CMA is enabled and HIGHMEM is disabled on the r8a7791 Koelsch hardware platform:

    WARNING: CPU: 1 PID: 1 at mm/cma.c:113 cma_init_reserved_areas+0x88/0x1d4()
    ...
    WARNING: CPU: 1 PID: 1 at mm/cma.c:121 cma_init_reserved_areas+0xf8/0x1d4()
    ...
    Unable to handle kernel NULL pointer dereference at virtual address 00000160
    pgd = c0003000
    [00000160] *pgd€000040004003, *pmd000000
    Internal error: Oops: 206 [#1] SMP ARM
    Modules linked in:
    CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W
3.19.0-rc4-koelsch-01450-g7f9b6075ce12c3ea-dirty #735
    Hardware name: Generic R8A7791 (Flattened Device Tree)
    task: edc553c0 ti: edc56000 task.ti: edc56000
    PC is at set_pfnblock_flags_mask+0x54/0xa0
    LR is at 0x440

In the current shmobile_defconfig HIGHMEM is enabled while CMA is disabled, so to trigger this the kernel configuration for both CMA and HIGHMEM needs to be adjusted.

Signed-off-by Magnus Damm <[email protected]>

Tested-by Geert Uytterhoeven <[email protected]>

---

Changes since V1:
- Included error log and Tested-by from Geert - thanks!

Written on top of renesas-devel-20150114v2-v3.19-rc4

 arch/arm/mach-shmobile/setup-rcar-gen2.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

arch/arm/mach-shmobile/setup-rcar-gen2.c +2 -1

@@ -21,6 +21,7 @@
 #include <linux/dma-contiguous.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/memblock.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <asm/mach/arch.h>

@@ -197,7 +198,7 @@ void __init rcar_gen2_reserve(void)
 
 	of_scan_flat_dt(rcar_gen2_scan_mem, &mrc);
 #ifdef CONFIG_DMA_CMA
-	if (mrc.size)
+	if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
 		dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
 					    &rcar_gen2_dma_contiguous, true);
 #endif