On Mon, Feb 24, 2025 at 04:39:06PM +0800, Stanley Chu wrote:
> From: Stanley Chu <yschu@xxxxxxxxxxx>
>
> 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@xxxxxxxxxxx>
> ---
> drivers/i3c/master/svc-i3c-master.c | 44 ++++++++++++++++++++---------
> 1 file changed, 31 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 8834f87a4767..07506ae0f914 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -942,7 +942,7 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
> u8 *addrs, unsigned int *count)
> {
> u64 prov_id[SVC_I3C_MAX_DEVS] = {}, nacking_prov_id = 0;
> - unsigned int dev_nb = 0, last_addr = 0;
> + unsigned int dev_nb = 0, last_addr = 0, dyn_addr;
> u32 reg;
> int ret, i;
>
> @@ -985,6 +985,17 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
> if (SVC_I3C_MSTATUS_RXPEND(reg)) {
> u8 data[6];
>
> + /*
> + * One slave sends its ID to request for address assignment,
> + * pre-filling the dynamic address can reduce SCL clock stalls
> + * and also fix the SVC_I3C_QUIRK_FIFO_EMPTY quirk.
> + */
> + dyn_addr = i3c_master_get_free_addr(&master->base, last_addr + 1);
> + if (dyn_addr < 0)
> + return -ENOSPC;
> +
> + writel(dyn_addr, master->regs + SVC_I3C_MWDATAB);
> +
Although there is 64 clock time after issue do_daa, it is still better if
prefill dyn_addr before sent do daa command?
If add a debug message before i3c_master_get_free_addr(), does it trigger
hardware issue?
Frank
> /*
> * We only care about the 48-bit provisioned ID yet to
> * be sure a device does not nack an address twice.
> @@ -1063,21 +1074,16 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
> if (ret)
> break;
>
> - /* Give the slave device a suitable dynamic address */
> - ret = i3c_master_get_free_addr(&master->base, last_addr + 1);
> - if (ret < 0)
> - break;
> -
> - addrs[dev_nb] = ret;
> + addrs[dev_nb] = dyn_addr;
> dev_dbg(master->dev, "DAA: device %d assigned to 0x%02x\n",
> dev_nb, addrs[dev_nb]);
> -
> - writel(addrs[dev_nb], master->regs + SVC_I3C_MWDATAB);
> last_addr = addrs[dev_nb++];
> }
>
> /* Need manual issue STOP except for Complete condition */
> svc_i3c_master_emit_stop(master);
> + svc_i3c_master_flush_fifo(master);
> +
> return ret;
> }
>
> @@ -1225,8 +1231,8 @@ 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;
> @@ -1243,7 +1249,7 @@ 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);
> @@ -1274,6 +1280,17 @@ static int svc_i3c_master_xfer(struct svc_i3c_master *master,
> SVC_I3C_MCTRL_RDTERM(*actual_len),
> master->regs + SVC_I3C_MCTRL);
>
> + if (svc_has_quirk(master, SVC_I3C_QUIRK_FIFO_EMPTY) && !rnw && xfer_len) {
> + u32 len = min_t(u32, xfer_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;
> + }
> +
The same here, you prefill data after issue sent out address, timing still
tight, only 9 SCL clock time. should it prefill before issue address?
Frank
> ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
> SVC_I3C_MSTATUS_MCTRLDONE(reg), 0, 1000);
> if (ret)
> @@ -1335,7 +1352,7 @@ 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;
>
> @@ -1362,6 +1379,7 @@ 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
>
