RE: [PATCH 3/4] i3c: master: svc: add support for slave to stop returning data

[Clark Wang <xiaoning.wang@nxp.com>]

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Hi Miquel,

Thanks for your review!

> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@bootlin.com>
> Sent: Friday, July 16, 2021 6:56
> To: Clark Wang <xiaoning.wang@nxp.com>
> Cc: conor.culhane@silvaco.com; alexandre.belloni@bootlin.com;
> vitor.soares@synopsys.com; boris.brezillon@bootlin.com; linux-
> i3c@lists.infradead.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 3/4] i3c: master: svc: add support for slave to stop
> returning data
> 
> Hi Clark,
> 
> Clark Wang <xiaoning.wang@nxp.com> wrote on Thu, 15 Jul 2021 16:24:12
> +0800:
> 
> > When i3c controller reads data from slave device, slave device can
> > stop returning data with an ACK after any byte.
> > Add this support for svc i3c controller. Otherwise, it will go TIMEOUT
> > error path when the slave device ends the read operation early.
> 
> Is this part of the I3C specification? I am not aware about it.

Yes. I think the spec mentions about this. You can check section "5.1.2.3 I3C SDR Data Words" of <mipi_i3c_basic_specification>.
[3. Ninth Bit of SDR Slave Returned (Read) Data as End-of-Data: In I2C, the ninth Data bit from
Slave to Master is an ACK by the Master. By contrast, in I3C this bit allows the Slave to end a
Read, and allows the Master to Abort a Read. In SDR terms, the ninth bit of Read data is referred
to as the T-Bit (for ‘Transition’) (see Section 5.1.2.3.4).]

Best Regards,
Clark Wang

> 
> > Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
> > ---
> >  drivers/i3c/master/svc-i3c-master.c | 28 ++++++++++++++++++++--------
> >  1 file changed, 20 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/i3c/master/svc-i3c-master.c
> > b/drivers/i3c/master/svc-i3c-master.c
> > index 9d80435638ea..892e57fec4b0 100644
> > --- a/drivers/i3c/master/svc-i3c-master.c
> > +++ b/drivers/i3c/master/svc-i3c-master.c
> > @@ -865,7 +865,7 @@ static int svc_i3c_master_read(struct
> svc_i3c_master *master,
> >  			       u8 *in, unsigned int len)
> >  {
> >  	int offset = 0, i, ret;
> > -	u32 mdctrl;
> > +	u32 mdctrl, mstatus;
> >
> >  	while (offset < len) {
> >  		unsigned int count;
> > @@ -874,8 +874,15 @@ static int svc_i3c_master_read(struct
> svc_i3c_master *master,
> >  					 mdctrl,
> >  					 !(mdctrl &
> SVC_I3C_MDATACTRL_RXEMPTY),
> >  					 0, 1000);
> > -		if (ret)
> > -			return ret;
> > +		if (ret) {
> > +			ret = readl_poll_timeout(master->regs +
> SVC_I3C_MSTATUS,
> > +				 mstatus,
> SVC_I3C_MSTATUS_COMPLETE(mstatus),
> > +				 0, 1000);
> > +			if (ret)
> > +				return ret;
> > +			else
> > +				return offset;
> > +		}
> >
> >  		count = SVC_I3C_MDATACTRL_RXCOUNT(mdctrl);
> >  		for (i = 0; i < count; i++)
> > @@ -884,7 +891,7 @@ static int svc_i3c_master_read(struct
> svc_i3c_master *master,
> >  		offset += count;
> >  	}
> >
> > -	return 0;
> > +	return offset;
> >  }
> >
> >  static int svc_i3c_master_write(struct svc_i3c_master *master, @@
> > -917,7 +924,7 @@ static int svc_i3c_master_write(struct svc_i3c_master
> > *master,  static int svc_i3c_master_xfer(struct svc_i3c_master *master,
> >  			       bool rnw, unsigned int xfer_type, u8 addr,
> >  			       u8 *in, const u8 *out, unsigned int xfer_len,
> > -			       unsigned int read_len, bool continued)
> > +			       unsigned int *read_len, bool continued)
> >  {
> >  	u32 reg;
> >  	int ret;
> > @@ -927,7 +934,7 @@ static int svc_i3c_master_xfer(struct svc_i3c_master
> *master,
> >  	       SVC_I3C_MCTRL_IBIRESP_NACK |
> >  	       SVC_I3C_MCTRL_DIR(rnw) |
> >  	       SVC_I3C_MCTRL_ADDR(addr) |
> > -	       SVC_I3C_MCTRL_RDTERM(read_len),
> > +	       SVC_I3C_MCTRL_RDTERM(*read_len),
> >  	       master->regs + SVC_I3C_MCTRL);
> >
> >  	ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
> @@
> > -939,8 +946,10 @@ static int svc_i3c_master_xfer(struct svc_i3c_master
> *master,
> >  		ret = svc_i3c_master_read(master, in, xfer_len);
> >  	else
> >  		ret = svc_i3c_master_write(master, out, xfer_len);
> > -	if (ret)
> > +	if (ret < 0)
> >  		goto emit_stop;
> > +	if (rnw)
> > +		*read_len = ret;
> >
> >  	ret = readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
> >  				 SVC_I3C_MSTATUS_COMPLETE(reg), 0,
> 1000); @@ -1012,7 +1021,7 @@
> > static void svc_i3c_master_start_xfer_locked(struct svc_i3c_master
> > *master)
> >
> >  		ret = svc_i3c_master_xfer(master, cmd->rnw, xfer->type,
> >  					  cmd->addr, cmd->in, cmd->out,
> > -					  cmd->len, cmd->read_len,
> > +					  cmd->len, &cmd->read_len,
> >  					  cmd->continued);
> >  		if (ret)
> >  			break;
> > @@ -1141,6 +1150,9 @@ static int
> svc_i3c_master_send_direct_ccc_cmd(struct svc_i3c_master *master,
> >  	if (!wait_for_completion_timeout(&xfer->comp,
> msecs_to_jiffies(1000)))
> >  		svc_i3c_master_dequeue_xfer(master, xfer);
> >
> > +	if (cmd->read_len != xfer_len)
> > +		ccc->dests[0].payload.len = cmd->read_len;
> > +
> >  	ret = xfer->ret;
> >  	svc_i3c_master_free_xfer(xfer);
> >
> 
> Thanks,
> Miquèl

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