950-0634-dma-contiguous-CMA-give-precedence-to-cmdline.patch

From cf40e83d2b6fb6857b13df4c8d69cc4c45395ea2 Mon Sep 17 00:00:00 2001
From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Date: Fri, 10 Jan 2020 18:19:33 +0100
Subject: [PATCH] dma-contiguous: CMA: give precedence to cmdline

commit 8c8c5a4994a306c217fd061cbfc5903399fd4c1c upstream.

Although the device tree might contain a reserved-memory DT node
dedicated as the default CMA pool, users might want to change CMA's
parameters using the kernel command line for debugging purposes and
whatnot. Honor this by bypassing the reserved memory CMA setup, which
will ultimately end up freeing the memblock and allow the command line
CMA configuration routine to run.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Phil Elwell <phil@raspberrypi.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/dma/contiguous.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -301,9 +301,16 @@ static int __init rmem_cma_setup(struct
 	phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
 	phys_addr_t mask = align - 1;
 	unsigned long node = rmem->fdt_node;
+	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
 	struct cma *cma;
 	int err;
 
+	if (size_cmdline != -1 && default_cma) {
+		pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n",
+			rmem->name);
+		return -EBUSY;
+	}
+
 	if (!of_get_flat_dt_prop(node, "reusable", NULL) ||
 	    of_get_flat_dt_prop(node, "no-map", NULL))
 		return -EINVAL;
@@ -321,7 +328,7 @@ static int __init rmem_cma_setup(struct
 	/* Architecture specific contiguous memory fixup. */
 	dma_contiguous_early_fixup(rmem->base, rmem->size);
 
-	if (of_get_flat_dt_prop(node, "linux,cma-default", NULL))
+	if (default_cma)
 		dma_contiguous_set_default(cma);
 
 	rmem->ops = &rmem_cma_ops;