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@aspeedtech.com>
---
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@aspeedtech.com
---
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@aspeedtech.com
---
 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@aspeedtech.com>

On Tue, 07 Apr 2026 16:53:23 +0800, Billy Tsai wrote:
> 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.
> 
> [...]

Applied, thanks!

[1/1] i3c: mipi-i3c-hci: fix IBI payload length calculation for final status
      https://git.kernel.org/i3c/c/d35a6db887ee

Best regards,

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

On Tue, Apr 07, 2026 at 04:53:23PM +0800, Billy Tsai wrote:
> 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@aspeedtech.com>
> ---
> 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@aspeedtech.com
> ---
> 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@aspeedtech.com
> ---
>  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);

this should be added to ibi_size reguardless chucks.

if (chunks)
	ibi_size += (chunks - 1) * rh->ibi_chunk_sz;

ibi_size += FIELD_GET(IBI_DATA_LENGTH, ibi_status);


Frank
> +			}
>  			last_ptr = ptr;
>  			break;
>  		}
>
> ---
> base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
> change-id: 20260331-i3c-hci-dma-3aae908b4e8e
>
> Best regards,
> --
> Billy Tsai <billy_tsai@aspeedtech.com>
>