Fix i2c ISMT DMA buffer alignment issue (sonic-net#123)

Add linux patch to fix i2c ISMT 16-byte alignment issue of the DMA buffer address.

Co-authored-by: lguohan <lguohan@gmail.com>

patch/fix_ismt_alignment_issue.patch

@@ -0,0 +1,141 @@
+From Commit ID: 5cd5f0bb0d9c32876b3d86b70fb45da10d028be7
+Subject: I2C ISMT  16-byte align the DMA buffer address
+
+Use only a portion of the data buffer for DMA transfers, which is always
+16-byte aligned. This makes the DMA buffer address 16-byte aligned and
+compensates for spurious hardware parity errors that may appear when the
+DMA buffer address is not 16-byte aligned.
+
+The data buffer is enlarged in order to accommodate any possible 16-byte
+alignment offset and changes the DMA code to only use a portion of the
+data buffer, which is 16-byte aligned.
+
+The symptom of the hardware issue is the same as the one addressed in
+v3.12-rc2-5-gbf41691 and manifests by transfers failing with EIO, with
+bit 9 being set in the ERRSTS register.
+
+Signed-off-by: Radu Rendec <radu.rendec@gmail.com>
+Acked-by: Neil Horman <nhorman@tuxdriver.com>
+Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
+---
+
+diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
+index c97b48c..91c6524 100644
+--- a/drivers/i2c/busses/i2c-ismt.c
++++ b/drivers/i2c/busses/i2c-ismt.c
+@@ -173,7 +173,7 @@ struct ismt_priv {
+ 	dma_addr_t io_rng_dma;			/* descriptor HW base addr */
+ 	u8 head;				/* ring buffer head pointer */
+ 	struct completion cmp;			/* interrupt completion */
+-	u8 dma_buffer[I2C_SMBUS_BLOCK_MAX + 1];	/* temp R/W data buffer */
++	u8 buffer[I2C_SMBUS_BLOCK_MAX + 16];	/* temp R/W data buffer */
+ };
+
+ /**
+@@ -324,7 +324,7 @@ static int ismt_process_desc(const struct ismt_desc *desc,
+ 			     struct ismt_priv *priv, int size,
+ 			     char read_write)
+ {
+-	u8 *dma_buffer = priv->dma_buffer;
++	u8 *dma_buffer = PTR_ALIGN(&priv->buffer[0], 16);
+
+ 	dev_dbg(&priv->pci_dev->dev, "Processing completed descriptor\n");
+ 	__ismt_desc_dump(&priv->pci_dev->dev, desc);
+@@ -397,6 +397,7 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 	struct ismt_desc *desc;
+ 	struct ismt_priv *priv = i2c_get_adapdata(adap);
+ 	struct device *dev = &priv->pci_dev->dev;
++	u8 *dma_buffer =  PTR_ALIGN(&priv->buffer[0], 16);
+
+ 	if (delay > 0)
+ 		udelay(delay);
+@@ -404,7 +405,7 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 	desc = &priv->hw[priv->head];
+
+ 	/* Initialize the DMA buffer */
+-	memset(priv->dma_buffer, 0, sizeof(priv->dma_buffer));
++	memset(priv->buffer, 0, sizeof(priv->buffer));
+
+ 	/* Initialize the descriptor */
+ 	memset(desc, 0, sizeof(struct ismt_desc));
+@@ -453,8 +454,8 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 			desc->wr_len_cmd = 2;
+ 			dma_size = 2;
+ 			dma_direction = DMA_TO_DEVICE;
+-			priv->dma_buffer[0] = command;
+-			priv->dma_buffer[1] = data->byte;
++			dma_buffer[0] = command;
++			dma_buffer[1] = data->byte;
+ 		} else {
+ 			/* Read Byte */
+ 			dev_dbg(dev, "I2C_SMBUS_BYTE_DATA:  READ\n");
+@@ -473,9 +474,9 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 			desc->wr_len_cmd = 3;
+ 			dma_size = 3;
+ 			dma_direction = DMA_TO_DEVICE;
+-			priv->dma_buffer[0] = command;
+-			priv->dma_buffer[1] = data->word & 0xff;
+-			priv->dma_buffer[2] = data->word >> 8;
++			dma_buffer[0] = command;
++			dma_buffer[1] = data->word & 0xff;
++			dma_buffer[2] = data->word >> 8;
+ 		} else {
+ 			/* Read Word */
+ 			dev_dbg(dev, "I2C_SMBUS_WORD_DATA:  READ\n");
+@@ -493,9 +494,9 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 		desc->rd_len = 2;
+ 		dma_size = 3;
+ 		dma_direction = DMA_BIDIRECTIONAL;
+-		priv->dma_buffer[0] = command;
+-		priv->dma_buffer[1] = data->word & 0xff;
+-		priv->dma_buffer[2] = data->word >> 8;
++		dma_buffer[0] = command;
++		dma_buffer[1] = data->word & 0xff;
++		dma_buffer[2] = data->word >> 8;
+ 		break;
+
+ 	case I2C_SMBUS_BLOCK_DATA:
+@@ -506,8 +507,8 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 			dma_direction = DMA_TO_DEVICE;
+ 			desc->wr_len_cmd = dma_size;
+ 			desc->control |= ISMT_DESC_BLK;
+-			priv->dma_buffer[0] = command;
+-			memcpy(&priv->dma_buffer[1], &data->block[1], dma_size - 1);
++			dma_buffer[0] = command;
++			memcpy(&dma_buffer[1], &data->block[1], dma_size - 1);
+ 		} else {
+ 			/* Block Read */
+ 			dev_dbg(dev, "I2C_SMBUS_BLOCK_DATA:  READ\n");
+@@ -534,8 +535,8 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 			dma_direction = DMA_TO_DEVICE;
+ 			desc->wr_len_cmd = dma_size;
+ 			desc->control |= ISMT_DESC_I2C;
+-			priv->dma_buffer[0] = command;
+-			memcpy(&priv->dma_buffer[1], &data->block[1], dma_size - 1);
++			dma_buffer[0] = command;
++			memcpy(&dma_buffer[1], &data->block[1], dma_size - 1);
+ 		} else {
+ 			/* i2c Block Read */
+ 			dev_dbg(dev, "I2C_SMBUS_I2C_BLOCK_DATA:  READ\n");
+@@ -564,18 +565,18 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
+ 	if (dma_size != 0) {
+ 		dev_dbg(dev, " dev=%p\n", dev);
+ 		dev_dbg(dev, " data=%p\n", data);
+-		dev_dbg(dev, " dma_buffer=%p\n", priv->dma_buffer);
++		dev_dbg(dev, " dma_buffer=%p\n", dma_buffer);
+ 		dev_dbg(dev, " dma_size=%d\n", dma_size);
+ 		dev_dbg(dev, " dma_direction=%d\n", dma_direction);
+
+ 		dma_addr = dma_map_single(dev,
+-				      priv->dma_buffer,
++				      dma_buffer,
+ 				      dma_size,
+ 				      dma_direction);
+
+ 		if (dma_mapping_error(dev, dma_addr)) {
+ 			dev_err(dev, "Error in mapping dma buffer %p\n",
+-				priv->dma_buffer);
++				dma_buffer);
+ 			return -EIO;
+ 		}
+

patch/series

@@ -104,6 +104,7 @@ net-psample-fix-skb-over-panic.patch
 net-backport-ipv6-missing-route.patch
 Support-for-fullcone-nat.patch
 driver-ixgbe-external-phy.patch
+fix_ismt_alignment_issue.patch
 #
 # This series applies on GIT commit 1451b36b2b0d62178e42f648d8a18131af18f7d8
 # Tkernel-sched-core-fix-cgroup-fork-race.patch