Blackfin: support smaller uncached DMA chunks for memory constrained systems

When working with 8 meg systems, forcing a 1 meg DMA chunk heavily cuts
into the available resources.  So support smaller chunks to better cover
needs for these systems.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

3 files changed, 25 insertions, 7 deletions

diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index d703247caf20..8141b1e82927 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -896,6 +896,12 @@ config DMA_UNCACHED_2M
         bool "Enable 2M DMA region"
 config DMA_UNCACHED_1M
         bool "Enable 1M DMA region"
+config DMA_UNCACHED_512K
+        bool "Enable 512K DMA region"
+config DMA_UNCACHED_256K
+        bool "Enable 256K DMA region"
+config DMA_UNCACHED_128K
+        bool "Enable 128K DMA region"
 config DMA_UNCACHED_NONE
         bool "Disable DMA region"
 endchoice
diff --git a/arch/blackfin/include/asm/bfin-global.h b/arch/blackfin/include/asm/bfin-global.h
index 741c02112c06..e6485c305ea6 100644
--- a/arch/blackfin/include/asm/bfin-global.h
+++ b/arch/blackfin/include/asm/bfin-global.h
@@ -20,6 +20,12 @@
 # define DMA_UNCACHED_REGION (2 * 1024 * 1024)
 #elif defined(CONFIG_DMA_UNCACHED_1M)
 # define DMA_UNCACHED_REGION (1024 * 1024)
+#elif defined(CONFIG_DMA_UNCACHED_512K)
+# define DMA_UNCACHED_REGION (512 * 1024)
+#elif defined(CONFIG_DMA_UNCACHED_256K)
+# define DMA_UNCACHED_REGION (256 * 1024)
+#elif defined(CONFIG_DMA_UNCACHED_128K)
+# define DMA_UNCACHED_REGION (128 * 1024)
 #else
 # define DMA_UNCACHED_REGION (0)
 #endif
diff --git a/arch/blackfin/kernel/cplb-nompu/cplbinit.c b/arch/blackfin/kernel/cplb-nompu/cplbinit.c
index fd9a2f31e686..c9b0a4d53dc1 100644
--- a/arch/blackfin/kernel/cplb-nompu/cplbinit.c
+++ b/arch/blackfin/kernel/cplb-nompu/cplbinit.c
@@ -89,15 +89,25 @@ void __init generate_cplb_tables_cpu(unsigned int cpu)
 
 void __init generate_cplb_tables_all(void)
 {
+        unsigned long uncached_end;
         int i_d, i_i;
 
         i_d = 0;
         /* Normal RAM, including MTD FS.  */
 #ifdef CONFIG_MTD_UCLINUX
-        dcplb_bounds[i_d].eaddr = memory_mtd_start + mtd_size;
+        uncached_end = memory_mtd_start + mtd_size;
 #else
-        dcplb_bounds[i_d].eaddr = memory_end;
+        uncached_end = memory_end;
 #endif
+        /*
+         * if DMA uncached is less than 1MB, mark the 1MB chunk as uncached
+         * so that we don't have to use 4kB pages and cause CPLB thrashing
+         */
+        if ((DMA_UNCACHED_REGION >= 1 * 1024 * 1024) || !DMA_UNCACHED_REGION ||
+            ((_ramend - uncached_end) >= 1 * 1024 * 1024))
+                dcplb_bounds[i_d].eaddr = uncached_end;
+        else
+                dcplb_bounds[i_d].eaddr = uncached_end & ~(1 * 1024 * 1024);
         dcplb_bounds[i_d++].data = SDRAM_DGENERIC;
         /* DMA uncached region.  */
         if (DMA_UNCACHED_REGION) {
@@ -135,11 +145,7 @@ void __init generate_cplb_tables_all(void)
 
         i_i = 0;
         /* Normal RAM, including MTD FS.  */
-#ifdef CONFIG_MTD_UCLINUX
-        icplb_bounds[i_i].eaddr = memory_mtd_start + mtd_size;
-#else
-        icplb_bounds[i_i].eaddr = memory_end;
-#endif
+        icplb_bounds[i_i].eaddr = uncached_end;
         icplb_bounds[i_i++].data = SDRAM_IGENERIC;
         /* DMA uncached region.  */
         if (DMA_UNCACHED_REGION) {