[PATCH v2 1/1] i3c: Add fallback method for GETMXDS CCC

Joshua Yeong
2023-11-14T03:35:37Z

Some I3C hardware will report error when incorrect length is received from
device. GETMXDS CCC are availble in 2 formats; without turnaround time (format
1) and with turnaround time (format 2). There is no mechanics to determine which
format is supported by device. In case sending GETMXDS CCC format 2 resulted
failure, try sending GETMXDS CCC format 1 instead.

Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
---
drivers/i3c/master.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 0cdc94e4cb77..2fc04d97f07e 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -1099,8 +1099,16 @@ static int i3c_master_getmxds_locked(struct i3c_master_controller *master,

i3c_ccc_cmd_init(&cmd, true, I3C_CCC_GETMXDS, &dest, 1);
ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
- if (ret)
- goto out;
+ if (ret) {
+ /*
+ * Retry when the device does not support max read turnaround
+ * while expecting shorter length from this CCC command
+ */
+ dest->payload.len -= 3;
+ ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
+ if (ret)
+ goto out;
+ }

if (dest.payload.len != 2 && dest.payload.len != 5) {
ret = -EIO;
--
2.25.1