RE: [PATCH v2] i3c: master: svc: adjust the first broadcast speed

[Carlos Song]

> -----Original Message-----
> From: Frank Li <frank.li@xxxxxxx>
> Sent: Saturday, July 20, 2024 2:26 AM
> To: Carlos Song <carlos.song@xxxxxxx>
> Cc: miquel.raynal@xxxxxxxxxxx; conor.culhane@xxxxxxxxxxx;
> alexandre.belloni@xxxxxxxxxxx; linux-i3c@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx; dl-linux-imx
> <linux-imx@xxxxxxx>
> Subject: Re: [PATCH v2] i3c: master: svc: adjust the first broadcast speed
> 
> On Fri, Jul 19, 2024 at 04:37:01PM +0000, Carlos Song wrote:
> >
> >
> > > -----Original Message-----
> > > From: Frank Li <frank.li@xxxxxxx>
> > > Sent: Friday, July 19, 2024 11:01 PM
> > > To: Carlos Song <carlos.song@xxxxxxx>
> > > Cc: miquel.raynal@xxxxxxxxxxx; conor.culhane@xxxxxxxxxxx;
> > > alexandre.belloni@xxxxxxxxxxx; linux-i3c@xxxxxxxxxxxxxxxxxxx;
> > > linux-kernel@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx; dl-linux-imx
> > > <linux-imx@xxxxxxx>
> > > Subject: Re: [PATCH v2] i3c: master: svc: adjust the first broadcast
> > > speed
> > >
> > > On Fri, Jul 19, 2024 at 04:03:51PM +0800, carlos.song@xxxxxxx wrote:
> > > > From: Carlos Song <carlos.song@xxxxxxx>
> > > >
> > > > According to the i3c spec 6.2 Timing Specification, the first
> > > > broadcast open drain timing should be adjust to High Period of SCL
> > > > Clock is 200ns at least. I3C device working as a i2c device will
> > > > see the broadcast to close its Spike Filter to change to i3c mode.
> > > > After that I3C open drain SCL high level should be adjust to 32ns~45ns.
> > > >
> > > > Signed-off-by: Carlos Song <carlos.song@xxxxxxx>
> > > > ---
> > > > Change for V2:
> > > > - use slow_speed instead of first_broadcast
> > > > - add default_speed variable in svc_i3c_xfer to avoid set default
> > > >   speed every time
> > > > - change start_xfer if else for easy understand
> > > > ---
> > > >  drivers/i3c/master/svc-i3c-master.c | 55
> > > > +++++++++++++++++++++++++++++
> > > >  1 file changed, 55 insertions(+)
> > > >
> > > > diff --git a/drivers/i3c/master/svc-i3c-master.c
> > > > b/drivers/i3c/master/svc-i3c-master.c
> > > > index 78116530f431..7cd3a9a4d7dd 100644
> > > > --- a/drivers/i3c/master/svc-i3c-master.c
> > > > +++ b/drivers/i3c/master/svc-i3c-master.c
> > > > @@ -142,6 +142,7 @@ struct svc_i3c_cmd {
> > > >  	unsigned int actual_len;
> > > >  	struct i3c_priv_xfer *xfer;
> > > >  	bool continued;
> > > > +	bool slow_address;
> > > >  };
> > > >
> > > >  struct svc_i3c_xfer {
> > > > @@ -214,6 +215,11 @@ struct svc_i3c_master {
> > > >  	} ibi;
> > > >  	struct mutex lock;
> > > >  	int enabled_events;
> > > > +
> > > > +	unsigned long fclk_rate;
> > > > +	u32 mctrl_config;
> > > > +	bool slow_speed;
> > > > +	bool default_speed;
> > >
> > > I think you needn't two varible 'slow_speed' and 'default_speed'.
> > > 	default_speed should always !slow_speed
> > >
> > > Frank
> > >
> >
> > Hi, Frank
> >
> > In fact, I am struggling for using just one variable: slow speed. Adding a
> variable "default_speed "was also a have-to move.
> >
> > If I use "if else" in xfer for easy understand, it means I only can change the
> MCTRL register value one time in every xfer. So in the first xfer, I must change
> slow_speed to false, then next xfer cmd->slow_address will be false. So in next
> xfer, I can set initial configuration back to the controller.
> > But the question is I have to set it every time, so I add the extra variable to
> avoid writel in every xfer.
> > It looks bad... Sorry for my poor coding.
> >
> > If only one variable " slow_speed " is used , I think "if else" and "writel one
> time", only one can be used. Maybe there is a better code method but I don't
> get it?
> 
> If I understand correct.
> 
> svc_i3c_master_set_slow_address_speed()
> {
> 	...
> 	master->slow_speed = true;
> }
> 
> svc_i3c_master_set_default_speed()
> {
> 	if (master->slow_speed) {
> 		writel();
> 		master->slow_speed false;
> 	}
> }
> 
>   if (cmd->slow_address)
> 	svc_i3c_master_set_slow_address_speed(master);
>   else
> 	svc_i3c_master_set_default_speed(master);
> 

Above logic will never enter the svc_i3c_master_set_default_speed(master);
Because this :
svc_i3c_master_send_bdcast_ccc_cmd(){
   if (master->slow_speed)
		cmd->slow_address = true;
   else
		cmd->slow_address = false;
}

Then svc_i3c_master_start_xfer_locked(){
	if (cmd->slow_address)
 		svc_i3c_master_set_slow_address_speed(master);
	else
 		svc_i3c_master_set_default_speed(master);
}

In svc_i3c_master_send_bdcast_ccc_cmd, we always need slow_speed to dicide cmd->slow_address is true or false. Then in svc_i3c_master_start_xfer_locked,
We use cmd->slow_address to chose set slow_speed or default speed.
when use "if else", it means we put slow_speed true->false into next xfer.

When first xfer finish, slow_speed is still true. So in next svc_i3c_master_send_bdcast_ccc_cmd:
then cmd->slow_address=ture, so in next xfer it will continue enter the "if" branch not the "else" branch:

if (cmd->slow_address)
 	svc_i3c_master_set_slow_address_speed(master);
else
 	svc_i3c_master_set_default_speed(master);

so whatever we need change master->slow_speed = false in the first xfer, don't put it into next xfer.
This is the reason I always do taht in my V1 V2 patch.

Carlos

> When slow_address is ture, always set slow_speed = ture when slow_address is
> false, call to set_sefault_speed, if previous
> 	slow_speed is true, then change to default speed, slow_speed will be false.
> 	when next time call to set_default_speed() do nothing.
> 
> Frank
> >
> > Carlos
> > > >  };
> > > >
> > > >  /**
> > > > @@ -531,6 +537,43 @@ static irqreturn_t
> > > > svc_i3c_master_irq_handler(int
> > > irq, void *dev_id)
> > > >  	return IRQ_HANDLED;
> > > >  }
> > > >
> > > > +static void svc_i3c_master_set_slow_address_speed(struct
> > > > +svc_i3c_master *master) {
> > > > +	struct i3c_bus *bus = i3c_master_get_bus(&master->base);
> > > > +	u32 ppbaud, odbaud, odhpp, mconfig;
> > > > +
> > > > +	master->mctrl_config = readl(master->regs + SVC_I3C_MCONFIG);
> > > > +	mconfig = master->mctrl_config;
> > > > +
> > > > +	/*
> > > > +	 * Set the I3C OPEN-DRAIN mode to the FM speed of 50%
> > > duty-cycle(400K/2500ns),
> > > > +	 * so that the first broadcast is visible to all devices on the i3c bus.
> > > > +	 * I3C device with 50ns filter will turn off the filter.
> > > > +	 */
> > > > +
> > > > +	ppbaud = FIELD_GET(GENMASK(11, 8), mconfig);
> > > > +	odhpp = 0;
> > > > +	odbaud = DIV_ROUND_UP(master->fclk_rate, bus->scl_rate.i2c * (2
> > > > ++ 2 *
> > > ppbaud)) - 1;
> > > > +	mconfig &= ~GENMASK(24, 16);
> > > > +	mconfig |= SVC_I3C_MCONFIG_ODBAUD(odbaud) |
> > > > +SVC_I3C_MCONFIG_ODHPP(odhpp);
> > > > +
> > > > +	writel(mconfig, master->regs + SVC_I3C_MCONFIG);
> > > > +	master->slow_speed = false;
> > > > +}
> > > > +
> > > > +static void svc_i3c_master_set_default_speed(struct
> > > > +svc_i3c_master
> > > > +*master) {
> > > > +	/*
> > > > +	 * The bus mode is already determined when the bus is
> > > > +initialized, so
> > > setting initial
> > > > +	 * configuration back to the controller. No need to set it in
> > > > +every transfer,
> > > just
> > > > +	 * restore it once time.
> > > > +	 */
> > > > +	if (!master->default_speed) {
> > > > +		writel(master->mctrl_config, master->regs +
> SVC_I3C_MCONFIG);
> > > > +		master->default_speed = true;
> > > > +	}
> > > > +}
> > > > +
> > > >  static int svc_i3c_master_bus_init(struct i3c_master_controller
> > > > *m) {
> > > >  	struct svc_i3c_master *master = to_svc_i3c_master(m); @@ -624,6
> > > > +667,8 @@ static int svc_i3c_master_bus_init(struct
> > > > +i3c_master_controller
> > > *m)
> > > >  	      SVC_I3C_MCONFIG_I2CBAUD(i2cbaud);
> > > >  	writel(reg, master->regs + SVC_I3C_MCONFIG);
> > > >
> > > > +	master->slow_speed = true;
> > > > +	master->fclk_rate = fclk_rate;
> > > >  	/* Master core's registration */
> > > >  	ret = i3c_master_get_free_addr(m, 0);
> > > >  	if (ret < 0)
> > > > @@ -1251,6 +1296,11 @@ static void
> > > svc_i3c_master_start_xfer_locked(struct svc_i3c_master *master)
> > > >  	for (i = 0; i < xfer->ncmds; i++) {
> > > >  		struct svc_i3c_cmd *cmd = &xfer->cmds[i];
> > > >
> > > > +		if (cmd->slow_address)
> > > > +			svc_i3c_master_set_slow_address_speed(master);
> > > > +		else
> > > > +			svc_i3c_master_set_default_speed(master);
> > > > +
> > > >  		ret = svc_i3c_master_xfer(master, cmd->rnw, xfer->type,
> > > >  					  cmd->addr, cmd->in, cmd->out,
> > > >  					  cmd->len, &cmd->actual_len, @@ -1346,6
> +1396,11 @@ static
> > > > int
> > > svc_i3c_master_send_bdcast_ccc_cmd(struct svc_i3c_master *master,
> > > >  	cmd->actual_len = 0;
> > > >  	cmd->continued = false;
> > > >
> > > > +	if (master->slow_speed)
> > > > +		cmd->slow_address = true;
> > > > +	else
> > > > +		cmd->slow_address = false;
> > > > +
> > > >  	mutex_lock(&master->lock);
> > > >  	svc_i3c_master_enqueue_xfer(master, xfer);
> > > >  	if (!wait_for_completion_timeout(&xfer->comp,
> > > > msecs_to_jiffies(1000)))
> > > > --
> > > > 2.34.1
> > > >