[PATCH v3 0/1] Fallback mechanism for GETMXDS CCC

[PATCH v3 0/1] Fallback mechanism for GETMXDS CCC

[Joshua Yeong]

Some I3C hardware does not support turnaround time in GETMXDS. Cadence IPs will
perform validation against length of CCC returned. Similar hardware error were
not seen in other IPs DW/SVC.

Joshua Yeong (1):
  i3c: Add fallback method for GETMXDS CCC

 drivers/i3c/master.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--
2.25.1


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[PATCH v3 1/1] i3c: Add fallback method for GETMXDS CCC

[Joshua Yeong]

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>
---
 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 95caa162706f..718b643cb54d 100644
--- 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;
-- 
2.25.1


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Re: [PATCH v3 1/1] i3c: Add fallback method for GETMXDS CCC

[Miquel Raynal]

Hi Joshua,

joshua.yeong@starfivetech.com wrote on Tue, 14 Nov 2023 16:55:25 +0800:

> 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.
> 

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>

> Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
> ---

Thanks,
Miquèl

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Re: [PATCH v3 0/1] Fallback mechanism for GETMXDS CCC

[Alexandre Belloni]

On Tue, 14 Nov 2023 16:55:24 +0800, Joshua Yeong wrote:
> Some I3C hardware does not support turnaround time in GETMXDS. Cadence IPs will
> perform validation against length of CCC returned. Similar hardware error were
> not seen in other IPs DW/SVC.
> 
> Joshua Yeong (1):
>   i3c: Add fallback method for GETMXDS CCC
> 
> [...]

Applied, thanks!

[1/1] i3c: Add fallback method for GETMXDS CCC
      commit: 2aac0bf4ebc8e09941bb2a40c0ce725437d9a82c

Best regards,

-- 
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Embedded Linux and Kernel engineering
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