linux-kernel - [PATCH v2 02/15] dmaengine: bcm2835: Add support for per-channel flags

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Date: Wed, 13 Mar 2024 15:08:27 +0100
From: Andrea della Porta <andrea.porta@...e.com>
To: Vinod Koul <vkoul@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Saenz Julienne <nsaenz@...nel.org>,
	dmaengine@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	dave.stevenson@...pberrypi.com
Cc: Phil Elwell <phil@...pberrypi.org>,
	Maxime Ripard <maxime@...no.tech>,
	Stefan Wahren <stefan.wahren@...e.com>,
	Dom Cobley <popcornmix@...il.com>,
	Andrea della Porta <andrea.porta@...e.com>
Subject: [PATCH v2 02/15] dmaengine: bcm2835: Add support for per-channel flags

From: Phil Elwell <phil@...pberrypi.org>

Add the ability to interpret the high bits of the dreq specifier as
flags to be included in the DMA_CS register. The motivation for this
change is the ability to set the DISDEBUG flag for SD card transfers
to avoid corruption when using the VPU debugger.

Signed-off-by: Phil Elwell <phil@...pberrypi.org>
Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
---
 drivers/dma/bcm2835-dma.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 428253b468ac..3d9973dd041d 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -137,6 +137,10 @@ struct bcm2835_desc {
 #define BCM2835_DMA_S_DREQ	BIT(10) /* enable SREQ for source */
 #define BCM2835_DMA_S_IGNORE	BIT(11) /* ignore source reads - read 0 */
 #define BCM2835_DMA_BURST_LENGTH(x) (((x) & 15) << 12)
+#define BCM2835_DMA_CS_FLAGS(x) ((x) & (BCM2835_DMA_PRIORITY(15) | \
+				      BCM2835_DMA_PANIC_PRIORITY(15) | \
+				      BCM2835_DMA_WAIT_FOR_WRITES | \
+				      BCM2835_DMA_DIS_DEBUG))
 #define BCM2835_DMA_PER_MAP(x)	(((x) & 31) << 16) /* REQ source */
 #define BCM2835_DMA_WAIT(x)	(((x) & 31) << 21) /* add DMA-wait cycles */
 #define BCM2835_DMA_NO_WIDE_BURSTS BIT(26) /* no 2 beat write bursts */
@@ -449,7 +453,8 @@ static void bcm2835_dma_start_desc(struct bcm2835_chan *c)
 	c->desc = to_bcm2835_dma_desc(&vd->tx);
 
 	writel(c->desc->cb_list[0].paddr, c->chan_base + BCM2835_DMA_ADDR);
-	writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
+	writel(BCM2835_DMA_ACTIVE | BCM2835_DMA_CS_FLAGS(c->dreq),
+	       c->chan_base + BCM2835_DMA_CS);
 }
 
 static irqreturn_t bcm2835_dma_callback(int irq, void *data)
@@ -476,7 +481,8 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
 	 * if this IRQ handler is threaded.) If the channel is finished, it
 	 * will remain idle despite the ACTIVE flag being set.
 	 */
-	writel(BCM2835_DMA_INT | BCM2835_DMA_ACTIVE,
+	writel(BCM2835_DMA_INT | BCM2835_DMA_ACTIVE |
+	       BCM2835_DMA_CS_FLAGS(c->dreq),
 	       c->chan_base + BCM2835_DMA_CS);
 
 	d = c->desc;
-- 
2.35.3