On Tue, Feb 25, 2025 at 05:28:48PM +0800, Stanley Chu wrote:
> On Tue, Feb 25, 2025 at 12:32 AM Frank Li <Frank.li@xxxxxxx> wrote:
> >
> > 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
>
> Ideally, prefilling before the processDAA command is better. However,
> it requires an additional check to write the dyn_addr at the right time
> because the driver needs to write the processDAA command twice for one
> assignment
>
> Prefilling here is safe and efficient because the FIFO starts filling
> within a few hundred nanoseconds on the npcm845, which is significantly
> faster compared to the 64 SCL clock cycles.
Okay, please this to comments.
>
>
> >
> > > /*
> > > * 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
>
> The entire transaction can consist of multiple read and write
> transfers. In the case
> of S+7E/W+Sr+dyn_addr/W+data+P, If the data is prefilled before Sr, it
> will be emitted
I think S+7E/W should be xfer[0]
Sr+dyn_addr/W + data + P should be xfer[1]
this function only handle one xfer each call. xfer[0]'s size is 0, no
pre fill data.
Only have prefill data at xfer[1].
> immediately and become part of the previous transfer.
>
> It is not a problem to fill FIFO here, the reason is the same as above.
> I will also modify the code as below to make it efficient and keep
> svc_i3c_master_write unchanged.
no issue to modify svc_i3c_master_write(). I consider prefill data before
actually.
This hardware is not prefect. Although it aleady in spin lock, it may run
some secuity firmware in secuity domain. There are 100us timeout. If a
hypervisor manage firmware interrupt transfer, one timeout may happen.
If prefill data before send address, it was safe at least for lenght less
than FIFO case.
Frank
>
> if (svc_has_quirk(master, SVC_I3C_QUIRK_FIFO_EMPTY) &&
> !rnw && xfer_len) {
> u32 len = min_t(u32, xfer_len, SVC_I3C_FIFO_SIZE);
>
> while (len--) {
> if (xfer_len == 1)
> writel(out[0], master->regs +
> SVC_I3C_MWDATABE);
> else
> writel(out[0], master->regs +
> SVC_I3C_MWDATAB);
> xfer_len--;
> out++;
> }
> }
>
>
> >
> > > 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
> > >
>
> --
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