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 45ad9b8..0d1c3ec 100644 (file)
--- a/drivers/i2c/busses/i2c-ismt.c
+++ b/drivers/i2c/busses/i2c-ismt.c
@@ -172,7 +172,7 @@ 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 */
 };
 
 /**
@@ -320,7 +320,7 @@ 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);
@@ -395,11 +395,12 @@ 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);
 
        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));
@@ -448,8 +449,8 @@ 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");
@@ -468,9 +469,9 @@ 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");
@@ -488,9 +489,9 @@ 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:
@@ -501,8 +502,8 @@ 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");
@@ -529,8 +530,8 @@ 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");
@@ -559,18 +560,18 @@ 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;
                }