[PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711

[Nicolas Saenz Julienne]

arm64 wants to be able to set ZONE_DMA's size depending on the specific
platform its being run on. Ideally this could be achieved in a smart way
by parsing all dma-ranges and calculating the smaller DMA constraint in
the system. Easier said than done. We compromised on a simpler solution
as the only platform interested in using this is the Raspberry Pi 4.

So update zone_dma_bits if the machine's compatible string matches
Raspberry Pi 4's, otherwise let arm64's mm code deal with it.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
 drivers/of/fdt.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 4602e467ca8b..cd0d115ef329 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -25,6 +25,7 @@
 #include <linux/serial_core.h>
 #include <linux/sysfs.h>
 #include <linux/random.h>
+#include <linux/dma-direct.h>	/* for zone_dma_bits */
 
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>
@@ -1198,6 +1199,14 @@ void __init early_init_dt_scan_nodes(void)
 	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
 }
 
+void __init early_init_dt_update_zone_dma_bits(void)
+{
+	unsigned long dt_root = of_get_flat_dt_root();
+
+	if (of_flat_dt_is_compatible(dt_root, "brcm,bcm2711"))
+		zone_dma_bits = 30;
+}
+
 bool __init early_init_dt_scan(void *params)
 {
 	bool status;
@@ -1207,6 +1216,7 @@ bool __init early_init_dt_scan(void *params)
 		return false;
 
 	early_init_dt_scan_nodes();
+	early_init_dt_update_zone_dma_bits();
 	return true;
 }
 
-- 
2.28.0