linux-kernel - [PATCH] dmaengine: sprd: Fix the link-list pointer register configuration issue

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Message-Id: <eadfe9295499efa003e1c344e67e2890f9d1d780.1568267061.git.baolin.wang@linaro.org>
Date:   Thu, 12 Sep 2019 13:47:18 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     vkoul@...nel.org
Cc:     orsonzhai@...il.com, zhang.lyra@...il.com,
        dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
        dmaengine@...r.kernel.org, eric.long@...soc.com,
        zhenfang.wang@...soc.com, baolin.wang@...aro.org
Subject: [PATCH] dmaengine: sprd: Fix the link-list pointer register configuration issue

From: Zhenfang Wang <zhenfang.wang@...soc.com>

We will set the link-list pointer register point to next link-list
configuration's physical address, which can load DMA configuration
from the link-list node automatically.

But the link-list node's physical address can be larger than 32bits,
and now Spreadtrum DMA driver only supports 32bits physical address,
which may cause loading a incorrect DMA configuration when starting
the link-list transfer mode. According to the DMA datasheet, we can
use SRC_BLK_STEP register (bit28 - bit31) to save the high bits of the
link-list node's physical address to fix this issue.

Fixes: 4ac695464763 ("dmaengine: sprd: Support DMA link-list mode")
Signed-off-by: Zhenfang Wang <zhenfang.wang@...soc.com>
Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
 drivers/dma/sprd-dma.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
index 525dc73..a4a91f2 100644
--- a/drivers/dma/sprd-dma.c
+++ b/drivers/dma/sprd-dma.c
@@ -134,6 +134,10 @@
 #define SPRD_DMA_SRC_TRSF_STEP_OFFSET	0
 #define SPRD_DMA_TRSF_STEP_MASK		GENMASK(15, 0)
 
+/* SPRD DMA_SRC_BLK_STEP register definition */
+#define SPRD_DMA_LLIST_HIGH_MASK	GENMASK(31, 28)
+#define SPRD_DMA_LLIST_HIGH_SHIFT	28
+
 /* define DMA channel mode & trigger mode mask */
 #define SPRD_DMA_CHN_MODE_MASK		GENMASK(7, 0)
 #define SPRD_DMA_TRG_MODE_MASK		GENMASK(7, 0)
@@ -717,6 +721,7 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
 	u32 int_mode = flags & SPRD_DMA_INT_MASK;
 	int src_datawidth, dst_datawidth, src_step, dst_step;
 	u32 temp, fix_mode = 0, fix_en = 0;
+	phys_addr_t llist_ptr;
 
 	if (dir == DMA_MEM_TO_DEV) {
 		src_step = sprd_dma_get_step(slave_cfg->src_addr_width);
@@ -814,13 +819,16 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
 		 * Set the link-list pointer point to next link-list
 		 * configuration's physical address.
 		 */
-		hw->llist_ptr = schan->linklist.phy_addr + temp;
+		llist_ptr = schan->linklist.phy_addr + temp;
+		hw->llist_ptr = lower_32_bits(llist_ptr);
+		hw->src_blk_step = (upper_32_bits(llist_ptr) << SPRD_DMA_LLIST_HIGH_SHIFT) &
+			SPRD_DMA_LLIST_HIGH_MASK;
 	} else {
 		hw->llist_ptr = 0;
+		hw->src_blk_step = 0;
 	}
 
 	hw->frg_step = 0;
-	hw->src_blk_step = 0;
 	hw->des_blk_step = 0;
 	return 0;
 }
-- 
1.7.9.5