i3c: Add fallback method for GETMXDS CCC

Some I3C hardware will report error when an incorrect length is received from
device. GETMXDS CCC are available 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. So in case sending GETMXDS CCC format 2 resulted
in a failure, try sending GETMXDS CCC format 1 instead.

Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20231114085525.6271-2-joshua.yeong@starfivetech.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 95caa162706f5543a91fb40cffaa2927b25b64c7..718b643cb54ddeaa37d029968cf0e13a044cac50 100644 (file)
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -1130,8 +1130,16 @@ 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;