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

On Thu, Oct 01, 2020 at 06:15:01PM +0100, Catalin Marinas wrote:

Hi Nicolas,

Thanks for putting this together.

On Thu, Oct 01, 2020 at 06:17:37PM +0200, Nicolas Saenz Julienne wrote:

quoted

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;
+}

I think we could keep this entirely in the arm64 setup_machine_fdt() and
not pollute the core code with RPi4-specific code.

Actually, even better, could we not move the check to
arm64_memblock_init() when we initialise zone_dma_bits?

-- 
Catalin