[PATCH v2 2/4] i3c: mipi-i3c-hci: Use core helpers for DMA mapping and bounce buffering

[Jarkko Nikula <jarkko.nikula@linux.intel.com>]

So far only I3C private and I2C transfers have required a bounce buffer
for DMA transfers when buffer is not DMA'able.

It was observed that when the device DMA is IOMMU mapped and the receive
length is not a multiple of DWORDs (32-bit), the last DWORD is padded
with stale data from the RX FIFO, corrupting 1-3 bytes beyond the
expected data.

A similar issue, though less severe, occurs when an I3C target returns
less data than requested. In this case, the padding does not exceed the
requested number of bytes, assuming the device DMA is not IOMMU mapped.

Therefore, all I3C private transfer, CCC command payload and I2C
transfer receive buffers must be properly sized for the DMA being IOMMU
mapped. Even if those buffers are already DMA safe, their size may not
be DWORD aligned.

To prepare for the device DMA being IOMMU mapped and to address the
above issue, use helpers from I3C core for DMA mapping and bounce
buffering for all DMA transfers.

For now, require bounce buffer only when the buffer is in the
vmalloc() area to avoid unnecessary copying with CCC commands and
DMA-safe I2C transfers.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
 drivers/i3c/master/mipi-i3c-hci/core.c | 34 --------------------------
 drivers/i3c/master/mipi-i3c-hci/dma.c  | 32 +++++++++---------------
 drivers/i3c/master/mipi-i3c-hci/hci.h  |  3 +--
 3 files changed, 13 insertions(+), 56 deletions(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
index 60f1175f1f37..b2977b6ac9f7 100644
--- a/drivers/i3c/master/mipi-i3c-hci/core.c
+++ b/drivers/i3c/master/mipi-i3c-hci/core.c
@@ -272,34 +272,6 @@ static int i3c_hci_daa(struct i3c_master_controller *m)
 	return hci->cmd->perform_daa(hci);
 }
 
-static int i3c_hci_alloc_safe_xfer_buf(struct i3c_hci *hci,
-				       struct hci_xfer *xfer)
-{
-	if (hci->io != &mipi_i3c_hci_dma ||
-	    xfer->data == NULL || !is_vmalloc_addr(xfer->data))
-		return 0;
-
-	if (xfer->rnw)
-		xfer->bounce_buf = kzalloc(xfer->data_len, GFP_KERNEL);
-	else
-		xfer->bounce_buf = kmemdup(xfer->data,
-					   xfer->data_len, GFP_KERNEL);
-
-	return xfer->bounce_buf == NULL ? -ENOMEM : 0;
-}
-
-static void i3c_hci_free_safe_xfer_buf(struct i3c_hci *hci,
-				       struct hci_xfer *xfer)
-{
-	if (hci->io != &mipi_i3c_hci_dma || xfer->bounce_buf == NULL)
-		return;
-
-	if (xfer->rnw)
-		memcpy(xfer->data, xfer->bounce_buf, xfer->data_len);
-
-	kfree(xfer->bounce_buf);
-}
-
 static int i3c_hci_priv_xfers(struct i3c_dev_desc *dev,
 			      struct i3c_priv_xfer *i3c_xfers,
 			      int nxfers)
@@ -333,9 +305,6 @@ static int i3c_hci_priv_xfers(struct i3c_dev_desc *dev,
 		}
 		hci->cmd->prep_i3c_xfer(hci, dev, &xfer[i]);
 		xfer[i].cmd_desc[0] |= CMD_0_ROC;
-		ret = i3c_hci_alloc_safe_xfer_buf(hci, &xfer[i]);
-		if (ret)
-			goto out;
 	}
 	last = i - 1;
 	xfer[last].cmd_desc[0] |= CMD_0_TOC;
@@ -359,9 +328,6 @@ static int i3c_hci_priv_xfers(struct i3c_dev_desc *dev,
 	}
 
 out:
-	for (i = 0; i < nxfers; i++)
-		i3c_hci_free_safe_xfer_buf(hci, &xfer[i]);
-
 	hci_free_xfer(xfer, nxfers);
 	return ret;
 }
diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
index 491dfe70b660..295671daae09 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dma.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
@@ -342,16 +342,11 @@ static int hci_dma_init(struct i3c_hci *hci)
 static void hci_dma_unmap_xfer(struct i3c_hci *hci,
 			       struct hci_xfer *xfer_list, unsigned int n)
 {
-	struct hci_xfer *xfer;
 	unsigned int i;
 
 	for (i = 0; i < n; i++) {
-		xfer = xfer_list + i;
-		if (!xfer->data)
-			continue;
-		dma_unmap_single(&hci->master.dev,
-				 xfer->data_dma, xfer->data_len,
-				 xfer->rnw ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
+		struct hci_xfer *xfer = xfer_list + i;
+		struct i3c_dma *dma_xfer __free(i3c_master_dma_unmap_single) = xfer->dma;
 	}
 }
 
@@ -362,7 +357,6 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
 	struct hci_rh_data *rh;
 	unsigned int i, ring, enqueue_ptr;
 	u32 op1_val, op2_val;
-	void *buf;
 
 	/* For now we only use ring 0 */
 	ring = 0;
@@ -373,6 +367,8 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
 	for (i = 0; i < n; i++) {
 		struct hci_xfer *xfer = xfer_list + i;
 		u32 *ring_data = rh->xfer + rh->xfer_struct_sz * enqueue_ptr;
+		enum dma_data_direction dir = xfer->rnw ? DMA_FROM_DEVICE :
+							  DMA_TO_DEVICE;
 
 		/* store cmd descriptor */
 		*ring_data++ = xfer->cmd_desc[0];
@@ -391,21 +387,17 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
 
 		/* 2nd and 3rd words of Data Buffer Descriptor Structure */
 		if (xfer->data) {
-			buf = xfer->bounce_buf ? xfer->bounce_buf : xfer->data;
-			xfer->data_dma =
-				dma_map_single(&hci->master.dev,
-					       buf,
-					       xfer->data_len,
-					       xfer->rnw ?
-						  DMA_FROM_DEVICE :
-						  DMA_TO_DEVICE);
-			if (dma_mapping_error(&hci->master.dev,
-					      xfer->data_dma)) {
+			xfer->dma = i3c_master_dma_map_single(&hci->master.dev,
+							      xfer->data,
+							      xfer->data_len,
+							      false,
+							      dir);
+			if (!xfer->dma) {
 				hci_dma_unmap_xfer(hci, xfer_list, i);
 				return -ENOMEM;
 			}
-			*ring_data++ = lower_32_bits(xfer->data_dma);
-			*ring_data++ = upper_32_bits(xfer->data_dma);
+			*ring_data++ = lower_32_bits(xfer->dma->addr);
+			*ring_data++ = upper_32_bits(xfer->dma->addr);
 		} else {
 			*ring_data++ = 0;
 			*ring_data++ = 0;
diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
index 69ea1d10414b..33bc4906df1f 100644
--- a/drivers/i3c/master/mipi-i3c-hci/hci.h
+++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
@@ -94,8 +94,7 @@ struct hci_xfer {
 		};
 		struct {
 			/* DMA specific */
-			dma_addr_t data_dma;
-			void *bounce_buf;
+			struct i3c_dma *dma;
 			int ring_number;
 			int ring_entry;
 		};
-- 
2.47.2


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