Re: [PATCH v1] i3c: master: svc: Fix npcm845 FIFO_EMPTY quirk

[Frank Li]

On Fri, Jul 25, 2025 at 03:03:10PM +0800, Stanley Chu wrote:
> From: Stanley Chu <yschu@xxxxxxxxxxx>
>
> Prefilling in private write transfers is only necessary when the FIFO
> is empty. Otherwise, if the transfer is NACKed due to IBIWON and retries
> continue, data may be prefilled again but could be lost because the FIFO
> is not empty.

why "maybe prefilled", please use certain words.

>
> Fixes: 4008a74e0f9b ("i3c: master: svc: Fix npcm845 FIFO empty issue")
> Signed-off-by: Stanley Chu <yschu@xxxxxxxxxxx>
> ---
>  drivers/i3c/master/svc-i3c-master.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 7e1a7cb94b43..34b6e125b18a 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -104,6 +104,7 @@
>  #define   SVC_I3C_MDATACTRL_TXTRIG_FIFO_NOT_FULL GENMASK(5, 4)
>  #define   SVC_I3C_MDATACTRL_RXTRIG_FIFO_NOT_EMPTY 0
>  #define   SVC_I3C_MDATACTRL_RXCOUNT(x) FIELD_GET(GENMASK(28, 24), (x))
> +#define   SVC_I3C_MDATACTRL_TXCOUNT(x) FIELD_GET(GENMASK(20, 16), (x))
>  #define   SVC_I3C_MDATACTRL_TXFULL BIT(30)
>  #define   SVC_I3C_MDATACTRL_RXEMPTY BIT(31)
>
> @@ -280,6 +281,13 @@ static inline bool is_events_enabled(struct svc_i3c_master *master, u32 mask)
>  	return !!(master->enabled_events & mask);
>  }
>
> +static inline bool svc_i3c_master_tx_empty(struct svc_i3c_master *master)
> +{
> +	u32 reg = readl(master->regs + SVC_I3C_MDATACTRL);
> +
> +	return (SVC_I3C_MDATACTRL_TXCOUNT(reg) == 0);
> +}
> +
>  static bool svc_i3c_master_error(struct svc_i3c_master *master)
>  {
>  	u32 mstatus, merrwarn;
> @@ -1303,7 +1311,8 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
>  		 * The only way to work around this hardware issue is to let the
>  		 * FIFO start filling as soon as possible after EmitStartAddr.
>  		 */
> -		if (svc_has_quirk(master, SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len) {
> +		if (svc_has_quirk(master, SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len &&
> +		    svc_i3c_master_tx_empty(master)) {
>  			u32 end = xfer_len > SVC_I3C_FIFO_SIZE ? 0 : SVC_I3C_MWDATAB_END;
>  			u32 len = min_t(u32, xfer_len, SVC_I3C_FIFO_SIZE);

if prefill to FIFO SIZE each time, such as

replace SVC_I3C_FIFO_SIZE with

SVC_I3C_FIFO_SIZE - SVC_I3C_MDATACTRL_TXCOUNT(readl(master->regs + SVC_I3C_MDATACTRL)).

Frank
>
> --
> 2.34.1
>