[PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype

[Magnus Damm <magnus.damm@gmail.com>]

From: Magnus Damm <damm+renesas@opensource.se>

This prototype patch extends the kernel to also reserve CMA memory
in the top memory bank on R-Car Gen2 boards and ties this larger
CMA area to the DU device for testing purpose.

This top portion of the memory requires 40-bits addressing support
in bus master devices including LPAE for the ARM CPU cores.

The patch assigns a 512 MiB CMA area to the DU device that may be
used with the IPMMU hardware to perform 40-bit bus master access.
Without IPMMU the DU hardware only supports 32-bit addresses.

Tested on r8a7791 Koelsch HDMI output using the modetest utility:
# modetest -M rcar-du -s 33:1024x768@AR24

Not for upstream merge.

Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
---

 arch/arm/mach-shmobile/setup-rcar-gen2.c |   33 ++++++++-
 drivers/staging/board/Makefile           |    1 
 drivers/staging/board/rcar-gen2.c        |  104 ++++++++++++++++++++++++++++++
 3 files changed, 134 insertions(+), 4 deletions(-)

--- 0001/arch/arm/mach-shmobile/setup-rcar-gen2.c
+++ work/arch/arm/mach-shmobile/setup-rcar-gen2.c	2015-12-19 09:38:09.750513000 +0900
@@ -136,14 +136,14 @@ struct memory_reserve_config {
 	u64 base, size;
 };
 
-static int __init rcar_gen2_scan_mem(unsigned long node, const char *uname,
-				     int depth, void *data)
+static int __init __rcar_gen2_scan_mem(unsigned long node, const char *uname,
+				     int depth, void *data,
+				     u64 lpae_start)
 {
 	const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
 	const __be32 *reg, *endp;
 	int l;
 	struct memory_reserve_config *mrc = data;
-	u64 lpae_start = 1ULL << 32;
 
 	/* We are scanning "memory" nodes only */
 	if (type = NULL || strcmp(type, "memory"))
@@ -182,6 +182,20 @@ static int __init rcar_gen2_scan_mem(uns
 	return 0;
 }
 
+static int __init rcar_gen2_scan_mem_legacy(unsigned long node,
+					    const char *uname,
+					    int depth, void *data)
+{
+	return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 32);
+}
+
+static int __init rcar_gen2_scan_mem_lpae(unsigned long node,
+					  const char *uname,
+					  int depth, void *data)
+{
+	return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 40);
+}
+
 struct cma *rcar_gen2_dma_contiguous;
 
 void __init rcar_gen2_reserve(void)
@@ -192,7 +206,18 @@ void __init rcar_gen2_reserve(void)
 	memset(&mrc, 0, sizeof(mrc));
 	mrc.reserved = SZ_256M;
 
-	of_scan_flat_dt(rcar_gen2_scan_mem, &mrc);
+	of_scan_flat_dt(rcar_gen2_scan_mem_legacy, &mrc);
+#ifdef CONFIG_DMA_CMA
+	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
+
+	/* reserve 512 MiB at the top of the 40-bit memory space */
+	memset(&mrc, 0, sizeof(mrc));
+	mrc.reserved = SZ_512M;
+
+	of_scan_flat_dt(rcar_gen2_scan_mem_lpae, &mrc);
 #ifdef CONFIG_DMA_CMA
 	if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
 		dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
--- 0001/drivers/staging/board/Makefile
+++ work/drivers/staging/board/Makefile	2015-12-18 17:46:31.030513000 +0900
@@ -1,3 +1,4 @@
 obj-y	:= board.o
 obj-$(CONFIG_ARCH_EMEV2)	+= kzm9d.o
 obj-$(CONFIG_ARCH_R8A7740)	+= armadillo800eva.o
+obj-$(CONFIG_ARCH_RCAR_GEN2)	+= rcar-gen2.o
--- /dev/null
+++ work/drivers/staging/board/rcar-gen2.c	2015-12-19 10:07:35.820513000 +0900
@@ -0,0 +1,104 @@
+/* Staging board support for R-Car Gen2. Enable not-yet-DT-capable bits here. */
+
+#include <linux/kernel.h>
+#include <linux/cma.h>
+#include <linux/dma-contiguous.h>
+#include <linux/errno.h>
+#include <linux/notifier.h>
+#include <linux/platform_device.h>
+#include "board.h"
+#include "../../../mm/cma.h"
+
+#if defined(CONFIG_CMA) && defined(CONFIG_DMA_CMA)
+
+static struct cma *largest_cma_area;
+
+static int cma_assign_bus_notifier(struct notifier_block *nb,
+			      unsigned long action, void *data)
+{
+	struct device *dev = data;
+	const struct device_node *node = dev->of_node;
+
+	if (action = BUS_NOTIFY_BIND_DRIVER) {
+		if (of_device_is_compatible(node, "renesas,du-r8a7790") ||
+		    of_device_is_compatible(node, "renesas,du-r8a7791") ||
+		    of_device_is_compatible(node, "renesas,du-r8a7793") ||
+		    of_device_is_compatible(node, "renesas,du-r8a7794")) {
+
+			pr_info("Board Staging: Assigning CMA to %s\n",
+				of_node_full_name(node));
+			dev_set_cma_area(dev, largest_cma_area);
+		}
+  	}
+
+	return 0;
+}
+
+static struct notifier_block cma_assign_nb = {
+	.notifier_call = cma_assign_bus_notifier,
+};
+
+struct cma *find_largest_nondefault_cma(void)
+{
+	unsigned long largest_size;
+	int k, largest_idx;
+
+	largest_size = 0;
+	largest_idx = -ENOENT;
+
+	for (k = 0; k < cma_area_count; k++) {
+		if (&cma_areas[k] = dma_contiguous_default_area)
+			continue;
+
+		if (cma_get_size(&cma_areas[k]) > largest_size) {
+			largest_size = cma_get_size(&cma_areas[k]);
+			largest_idx = k;
+		}
+	}
+
+	if (largest_idx != -ENOENT)
+		return &cma_areas[largest_idx];
+
+	return NULL;
+}
+
+static void __init board_staging_init(void)
+{
+	struct cma *target;
+	phys_addr_t cma_base;
+
+	target = find_largest_nondefault_cma();
+
+	if (target) {
+		cma_base = cma_get_base(target);
+
+		pr_info("Board Staging: Located CMA at "
+			"%pa, size %ld MiB\n", &cma_base,
+			(unsigned long)cma_get_size(target) / SZ_1M);
+
+		largest_cma_area = target;
+		bus_register_notifier(&platform_bus_type, &cma_assign_nb);
+	}
+}
+#else
+static inline void __init board_staging_init(void) {}
+#endif
+
+static int __init runtime_board_check(void)
+{
+	if (of_machine_is_compatible("renesas,r8a7790"))
+	       board_staging_init();
+
+	if (of_machine_is_compatible("renesas,r8a7791"))
+	       board_staging_init();
+
+	if (of_machine_is_compatible("renesas,r8a7793"))
+	       board_staging_init();
+
+	if (of_machine_is_compatible("renesas,r8a7794"))
+	       board_staging_init();
+
+	return 0;
+}
+
+arch_initcall(runtime_board_check)