linux-kernel - [PATCH RFC 3/5] ARM: let machines select dma-direct over arch's DMA implementation

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Message-Id: <20191014183108.24804-4-nsaenzjulienne@suse.de>
Date:   Mon, 14 Oct 2019 20:31:05 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Robin Murphy <robin.murphy@....com>,
        linux-arm-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Cc:     hch@...radead.org, mbrugger@...e.com, f.fainelli@...il.com,
        wahrenst@....net, Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Russell King <linux@...linux.org.uk>
Subject: [PATCH RFC 3/5] ARM: let machines select dma-direct over arch's DMA implementation

A bounce buffering feature is already available in ARM, dmabounce.c, yet
it doesn't support high memory which some devices need. Instead of
fixing it, provide a means for devices to enable dma-direct, which is the
preferred way of doing DMA now days.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
---
 arch/arm/include/asm/mach/arch.h | 1 +
 arch/arm/mm/init.c               | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
index e7df5a822cab..3542bf502573 100644
--- a/arch/arm/include/asm/mach/arch.h
+++ b/arch/arm/include/asm/mach/arch.h
@@ -33,6 +33,7 @@ struct machine_desc {
 #ifdef CONFIG_ZONE_DMA
 	phys_addr_t		dma_zone_size;	/* size of DMA-able area */
 #endif
+	bool			dma_direct;
 
 	unsigned int		video_start;	/* start of video RAM	*/
 	unsigned int		video_end;	/* end of video RAM	*/
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 0a63379a4d1a..556f70665353 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -19,6 +19,7 @@
 #include <linux/gfp.h>
 #include <linux/memblock.h>
 #include <linux/dma-contiguous.h>
+#include <linux/dma-direct.h>
 #include <linux/sizes.h>
 #include <linux/stop_machine.h>
 #include <linux/swiotlb.h>
@@ -119,6 +120,8 @@ void __init setup_dma_zone(const struct machine_desc *mdesc)
 	 */
 	if (IS_ENABLED(CONFIG_ARM_LPAE))
 		arm_dma_direct = true;
+	else
+		arm_dma_direct = mdesc->dma_direct;
 
 #ifdef CONFIG_ZONE_DMA
 	if (mdesc->dma_zone_size) {
@@ -126,7 +129,10 @@ void __init setup_dma_zone(const struct machine_desc *mdesc)
 		arm_dma_limit = PHYS_OFFSET + arm_dma_zone_size - 1;
 	} else
 		arm_dma_limit = 0xffffffff;
+
 	arm_dma_pfn_limit = arm_dma_limit >> PAGE_SHIFT;
+
+	zone_dma_bits = ilog2(arm_dma_limit) + 1;
 #endif
 }
 
@@ -482,7 +488,7 @@ static void __init free_highpages(void)
  */
 void __init mem_init(void)
 {
-#ifdef CONFIG_ARM_LPAE
+#ifdef CONFIG_SWIOTLB
 	swiotlb_init(1);
 #endif
 
-- 
2.23.0