[EXT] Re: [PATCH v2 1/2] i3c: master: support to adjust first broadcast address speed

[Carlos Song]

> -----Original Message-----
> From: Miquel Raynal <miquel.raynal at bootlin.com>
> Sent: Thursday, August 22, 2024 12:07 AM
> To: Carlos Song <carlos.song at nxp.com>
> Cc: alexandre.belloni at bootlin.com; Frank Li <frank.li at nxp.com>;
> conor.culhane at silvaco.com; linux-i3c at lists.infradead.org;
> linux-kernel at vger.kernel.org; imx at lists.linux.dev; dl-linux-imx
> <linux-imx at nxp.com>
> Subject: [EXT] Re: [PATCH v2 1/2] i3c: master: support to adjust first broadcast
> address speed
> 
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> 
> Hi carlos.song at nxp.com,
> 
> carlos.song at nxp.com wrote on Wed,  7 Aug 2024 14:13:05 +0800:
> 
> > From: Carlos Song <carlos.song at nxp.com>
> >
> > According to I3C spec 6.2 Timing Specification, the Open Drain High
> > Period of SCL Clock timing for first broadcast address should be
> > adjusted to 200ns at least. I3C device working as i2c device will see
> > the broadcast to close its Spike Filter then change to work at I3C
> > mode. After that I3C open drain SCL high level should be adjusted back.
> >
> > Signed-off-by: Carlos Song <carlos.song at nxp.com>
> > Reviewed-by: Frank Li <Frank.Li at nxp.com>
> > ---
> > - Fix set_speed description from Frank's comment
> > ---
> >  drivers/i3c/master.c       | 12 ++++++++++++
> >  include/linux/i3c/master.h | 18 ++++++++++++++++++
> >  2 files changed, 30 insertions(+)
> >
> > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c index
> > 7028f03c2c42..6f3eb710a75d 100644
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -1868,6 +1868,12 @@ static int i3c_master_bus_init(struct
> i3c_master_controller *master)
> >               goto err_bus_cleanup;
> >       }
> >
> > +     if (master->ops->set_speed) {
> > +             ret = master->ops->set_speed(master,
> I3C_OPEN_DRAIN_SLOW_SPEED);
> > +             if (ret)
> > +                     goto err_bus_cleanup;
> > +     }
> > +
> >       /*
> >        * Reset all dynamic address that may have been assigned before
> >        * (assigned by the bootloader for example).
> > @@ -1876,6 +1882,12 @@ static int i3c_master_bus_init(struct
> i3c_master_controller *master)
> >       if (ret && ret != I3C_ERROR_M2)
> >               goto err_bus_cleanup;
> >
> > +     if (master->ops->set_speed) {
> > +             master->ops->set_speed(master,
> I3C_OPEN_DRAIN_NORMAL_SPEED);
> > +             if (ret)
> > +                     goto err_bus_cleanup;
> > +     }
> > +
> >       /* Disable all slave events before starting DAA. */
> >       ret = i3c_master_disec_locked(master, I3C_BROADCAST_ADDR,
> >                                     I3C_CCC_EVENT_SIR |
> > I3C_CCC_EVENT_MR | diff --git a/include/linux/i3c/master.h
> > b/include/linux/i3c/master.h index 074f632868d9..b8daf09a9a4a 100644
> > --- a/include/linux/i3c/master.h
> > +++ b/include/linux/i3c/master.h
> > @@ -277,6 +277,20 @@ enum i3c_bus_mode {
> >       I3C_BUS_MODE_MIXED_SLOW,
> >  };
> >
> > +/**
> > + * enum i3c_open_drain_speed - I3C open drain speed
> > + * @I3C_OPEN_DRAIN_SLOW_SPEED: Slow open drain speed for First
> Broadcast Address.
> 
> A few minor style comments:
> 
> open-drain
> 
> ...for sending the first broadcast address.
> 
> > + *                           First Broadcast Address in this speed is
> visible to all I2C/I3C
> 
> The first broadcast address at this speed will be visible to all
> 
> > + *                           devices on the I3C bus. I3C device working
> as a I2C device will
> 
> ... I3C devices working in I2C mode will
> 
> > + *                           turn off its 50ns Spike Filter to change to
> work in I3C mode.
> 
>                                         their     spike filter when
>                                         switching into I3C mode.
> 
> > + * @I3C_OPEN_DRAIN_NORMAL_SPEED: Normal open drain speed
> configured
> > + according to
> 
> open-drain
> 
> > + *                           I3C bus mode.
> 
> I'm sorry, can you rephrase "configured according to I3C bus mode" ?
> 

Hi! Thank you for your ack! I will change above to:

/**
 * enum i3c_open_drain_speed - I3C open-drain speed
 * @I3C_OPEN_DRAIN_SLOW_SPEED: Slow open-drain speed for sending the first
 *				broadcast address. The first broadcast address at this speed
 *				will be visible to all devices on the I3C bus. I3C devices
 *				working in I2C mode will turn off their spike filter when		  
 *				switching into I3C mode.
 * @I3C_OPEN_DRAIN_NORMAL_SPEED: Normal open-drain speed in I3C bus mode.
 */

Is this acceptable?

> > + */
> > +enum i3c_open_drain_speed {
> > +     I3C_OPEN_DRAIN_SLOW_SPEED,
> > +     I3C_OPEN_DRAIN_NORMAL_SPEED,
> > +};
> > +
> >  /**
> >   * enum i3c_addr_slot_status - I3C address slot status
> >   * @I3C_ADDR_SLOT_FREE: address is free @@ -436,6 +450,9 @@ struct
> > i3c_bus {
> >   *                 NULL.
> >   * @enable_hotjoin: enable hot join event detect.
> >   * @disable_hotjoin: disable hot join event detect.
> > + * @set_speed: adjust I3C bus speed, which is generally used for reducing
> the speed
> > + *           for first broardcast address.
> > + *
> >   */
> >  struct i3c_master_controller_ops {
> >       int (*bus_init)(struct i3c_master_controller *master); @@ -464,6
> > +481,7 @@ struct i3c_master_controller_ops {
> >                                struct i3c_ibi_slot *slot);
> >       int (*enable_hotjoin)(struct i3c_master_controller *master);
> >       int (*disable_hotjoin)(struct i3c_master_controller *master);
> > +     int (*set_speed)(struct i3c_master_controller *master, enum
> > + i3c_open_drain_speed speed);
> >  };
> >
> >  /**
> 
> Otherwise lgtm.
> 
> Thanks,
> Miquèl