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

Miquel Raynal
2023-11-14T08:20:08Z

Hi Joshua,

joshua.yeong@starfivetech.com wrote on Tue, 14 Nov 2023 11:34:30 +0800:

> Some I3C hardware will report error when incorrect length is received from

an

> device. GETMXDS CCC are availble in 2 formats; without turnaround time (format

available :

> 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

So in case?

> failure, try sending GETMXDS CCC format 1 instead.

in a

>
> 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) {
> + /*
^
Wrong alignment of the starts below
v
> + * Retry when the device does not support max read turnaround
> + * while expecting shorter length from this CCC command

period?

> + */
> + dest->payload.len -= 3;
> + ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
> + if (ret)
> + goto out;
> + }

I believe this is a per-device configuration and we should save this in
order to only fail once, no?

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

Thanks,
Miquèl