linux-kernel - Re: [PATCH RESEND v2 3/4] i3c: master: svc: Fix npcm845 FIFO empty issue

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Message-ID: <Z7dstL6FBYh3/cz7@lizhi-Precision-Tower-5810>
Date: Thu, 20 Feb 2025 12:56:04 -0500
From: Frank Li <Frank.li@....com>
To: Stanley Chu <stanley.chuys@...il.com>
Cc: miquel.raynal@...tlin.com, alexandre.belloni@...tlin.com,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, tomer.maimon@...oton.com,
	kwliu@...oton.com, yschu@...oton.com
Subject: Re: [PATCH RESEND v2 3/4] i3c: master: svc: Fix npcm845 FIFO empty
 issue

On Thu, Feb 20, 2025 at 02:11:06PM +0800, Stanley Chu wrote:
> From: Stanley Chu <yschu@...oton.com>
>
> I3C HW stalls the write transfer if the transmit FIFO becomes empty,
> when new data is written to FIFO, I3C HW resumes the transfer but the
> first transmitted data bit may have the wrong value.
> Fill the FIFO in advance to prevent FIFO from becoming empty.
>
> Signed-off-by: Stanley Chu <yschu@...oton.com>
> ---

You missed do_daa part.

>  drivers/i3c/master/svc-i3c-master.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index c58440061d5a..2140da3f5187 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -1196,8 +1196,8 @@ static int svc_i3c_master_read(struct svc_i3c_master *master,
>  	return offset;
>  }
>
> -static int svc_i3c_master_write(struct svc_i3c_master *master,
> -				const u8 *out, unsigned int len)
> +static int svc_i3c_master_write(struct svc_i3c_master *master, const u8 *out,
> +				unsigned int len, bool last)
>  {
>  	int offset = 0, ret;
>  	u32 mdctrl;
> @@ -1214,7 +1214,7 @@ static int svc_i3c_master_write(struct svc_i3c_master *master,
>  		 * The last byte to be sent over the bus must either have the
>  		 * "end" bit set or be written in MWDATABE.
>  		 */
> -		if (likely(offset < (len - 1)))
> +		if (likely(offset < (len - 1)) || !last)
>  			writel(out[offset++], master->regs + SVC_I3C_MWDATAB);
>  		else
>  			writel(out[offset++], master->regs + SVC_I3C_MWDATABE);
> @@ -1245,6 +1245,19 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
>  		       SVC_I3C_MCTRL_RDTERM(*actual_len),
>  		       master->regs + SVC_I3C_MCTRL);
>
> +		if ((master->quirks & SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len) {
> +			unsigned int len = xfer_len;

len = max_t(u32, xfer_len, SVC_I3C_FIFO_SIZE);

> +
> +			if (xfer_len > SVC_I3C_FIFO_SIZE)
> +				len = SVC_I3C_FIFO_SIZE;
> +			ret = svc_i3c_master_write(master, out, len,
> +						   xfer_len <= SVC_I3C_FIFO_SIZE);
> +			if (ret < 0)
> +				goto emit_stop;
> +			xfer_len -= len;
> +			out += len;
> +		}
> +
>  		ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
>  				 SVC_I3C_MSTATUS_MCTRLDONE(reg), 0, 1000);
>  		if (ret)
> @@ -1306,7 +1319,7 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
>  	if (rnw)
>  		ret = svc_i3c_master_read(master, in, xfer_len);
>  	else
> -		ret = svc_i3c_master_write(master, out, xfer_len);
> +		ret = svc_i3c_master_write(master, out, xfer_len, true);
>  	if (ret < 0)
>  		goto emit_stop;
>
> @@ -1333,6 +1346,7 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
>  emit_stop:
>  	svc_i3c_master_emit_stop(master);
>  	svc_i3c_master_clear_merrwarn(master);
> +	svc_i3c_master_flush_fifo(master);
>
>  	return ret;
>  }
> --
> 2.34.1
>