Commit 5cd5f0bb authored by Radu Rendec's avatar Radu Rendec Committed by Wolfram Sang
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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: default avatarRadu Rendec <radu.rendec@gmail.com>
Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 38a99bd7

drivers/i2c/busses/i2c-ismt.c

+19 −18
Original line number Diff line number Diff line
@@ -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;

		}

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