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

Nicolas Saenz Julienne
2020-10-01T16:18:01Z

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@suse.de>
---
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