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From:   Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To:     robh+dt@kernel.org, catalin.marinas@arm.com, hch@lst.de,
        robin.murphy@arm.com, devicetree@vger.kernel.org,
        iommu@lists.linux-foundation.org, linux-mm@kvack.org,
        Frank Rowand <frowand.list@gmail.com>
Cc:     will@kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-rpi-kernel@lists.infradead.org,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711
Date:   Thu,  1 Oct 2020 18:17:37 +0200
Message-Id: <20201001161740.29064-2-nsaenzjulienne@suse.de>
In-Reply-To: <20201001161740.29064-1-nsaenzjulienne@suse.de>
References: <20201001161740.29064-1-nsaenzjulienne@suse.de>
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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