[PATCH v2] i3c: mipi-i3c-hci: fix IBI payload length calculation for final status

[Billy Tsai]

In DMA mode, the IBI status descriptor encodes the payload using
CHUNKS (number of chunks) and DATA_LENGTH (valid bytes in the last
chunk). All preceding chunks are implicitly full-sized.

The current code accumulates full chunk sizes for non-final status
descriptors, but for the final status descriptor it only adds
DATA_LENGTH. This ignores the contribution of the preceding full
chunks described by the same final status entry.

As a result, the computed IBI payload length is truncated whenever
the final status spans multiple chunks. For example, with a chunk
size of 4 bytes, CHUNKS=2 and DATA_LENGTH=1 should result in a total
payload size of 5 bytes, but the current code reports only 1 byte.

Fix the calculation by adding the size of (CHUNKS - 1) full chunks
plus DATA_LENGTH for the last chunk.

Fixes: 9ad9a52cce28 ("i3c/master: introduce the mipi-i3c-hci driver")
Signed-off-by: Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
---
Changes in v2:
- EDITME: describe what is new in this series revision.
- EDITME: use bulletpoints and terse descriptions.
- Link to v1: https://lore.kernel.org/r/20260331-i3c-hci-dma-v1-1-e5cd295c44ff@xxxxxxxxxxxxxx
---
Changes in v2:
- Fix IBI processing logic to properly handle IBIs without data payload.
- Link to v1: https://lore.kernel.org/r/20260331-i3c-hci-dma-v1-1-e5cd295c44ff@xxxxxxxxxxxxxx
---
 drivers/i3c/master/mipi-i3c-hci/dma.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
index b903a2da1fd1..c7272155c486 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dma.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
@@ -721,7 +721,10 @@ static void hci_dma_process_ibi(struct i3c_hci *hci, struct hci_rh_data *rh)
 		if (!(ibi_status & IBI_LAST_STATUS)) {
 			ibi_size += chunks * rh->ibi_chunk_sz;
 		} else {
-			ibi_size += FIELD_GET(IBI_DATA_LENGTH, ibi_status);
+			if (chunks) {
+				ibi_size += (chunks - 1) * rh->ibi_chunk_sz;
+				ibi_size += FIELD_GET(IBI_DATA_LENGTH, ibi_status);
+			}
 			last_ptr = ptr;
 			break;
 		}

---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260331-i3c-hci-dma-3aae908b4e8e

Best regards,
-- 
Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>