linux-kernel - [PATCH v3 2/4] Revert "dmaengine: imx-sdma: alloclate bd memory from dma pool"

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Date:   Tue, 6 Nov 2018 03:40:28 +0000
From:   Robin Gong <yibin.gong@....com>
To:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
CC:     "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: [PATCH v3 2/4] Revert "dmaengine: imx-sdma: alloclate bd memory from
 dma pool"

From: Lucas Stach <l.stach@...gutronix.de>

This reverts commit fe5b85c656bc. The SDMA engine needs the descriptors to
be contiguous in memory. As the dma pool API is only able to provide a
single descriptor per alloc invocation there is no guarantee that multiple
descriptors satisfy this requirement. Also the code in question is broken
as it only allocates memory for a single descriptor, without looking at the
number of descriptors required for the transfer, leading to out-of-bounds
accesses when the descriptors are written.

Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
Signed-off-by: Robin Gong <yibin.gong@....com>
---
 drivers/dma/imx-sdma.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index 3bca5e0..8d2fec8 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -24,7 +24,6 @@
 #include <linux/spinlock.h>
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
-#include <linux/dmapool.h>
 #include <linux/firmware.h>
 #include <linux/slab.h>
 #include <linux/platform_device.h>
@@ -376,7 +375,6 @@ struct sdma_channel {
 	u32				shp_addr, per_addr;
 	enum dma_status			status;
 	struct imx_dma_data		data;
-	struct dma_pool			*bd_pool;
 };
 
 #define IMX_DMA_SG_LOOP		BIT(0)
@@ -1192,10 +1190,11 @@ static int sdma_request_channel0(struct sdma_engine *sdma)
 
 static int sdma_alloc_bd(struct sdma_desc *desc)
 {
+	u32 bd_size = desc->num_bd * sizeof(struct sdma_buffer_descriptor);
 	int ret = 0;
 
-	desc->bd = dma_pool_alloc(desc->sdmac->bd_pool, GFP_ATOMIC,
-					&desc->bd_phys);
+	desc->bd = dma_zalloc_coherent(NULL, bd_size, &desc->bd_phys,
+					GFP_ATOMIC);
 	if (!desc->bd) {
 		ret = -ENOMEM;
 		goto out;
@@ -1206,7 +1205,9 @@ static int sdma_alloc_bd(struct sdma_desc *desc)
 
 static void sdma_free_bd(struct sdma_desc *desc)
 {
-	dma_pool_free(desc->sdmac->bd_pool, desc->bd, desc->bd_phys);
+	u32 bd_size = desc->num_bd * sizeof(struct sdma_buffer_descriptor);
+
+	dma_free_coherent(NULL, bd_size, desc->bd, desc->bd_phys);
 }
 
 static void sdma_desc_free(struct virt_dma_desc *vd)
@@ -1272,10 +1273,6 @@ static int sdma_alloc_chan_resources(struct dma_chan *chan)
 	if (ret)
 		goto disable_clk_ahb;
 
-	sdmac->bd_pool = dma_pool_create("bd_pool", chan->device->dev,
-				sizeof(struct sdma_buffer_descriptor),
-				32, 0);
-
 	return 0;
 
 disable_clk_ahb:
@@ -1304,9 +1301,6 @@ static void sdma_free_chan_resources(struct dma_chan *chan)
 
 	clk_disable(sdma->clk_ipg);
 	clk_disable(sdma->clk_ahb);
-
-	dma_pool_destroy(sdmac->bd_pool);
-	sdmac->bd_pool = NULL;
 }
 
 static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac,
-- 
2.7.4