linux-kernel - RE: [PATCH 2/3] i3c: add mixed limited bus mode

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Date:   Tue, 16 Apr 2019 14:27:10 +0000
From:   Vitor Soares <vitor.soares@...opsys.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>,
        Vitor Soares <vitor.soares@...opsys.com>
CC:     "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
        "joao.pinto@...opsys.com" <joao.pinto@...opsys.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/3] i3c: add mixed limited bus mode

Hi Boris,

From: Boris Brezillon <boris.brezillon@...labora.com>
Date: Tue, Apr 16, 2019 at 07:00:49

> Hi Vitor,
> 
> On Mon, 15 Apr 2019 20:46:42 +0200
> Vitor Soares <vitor.soares@...opsys.com> wrote:
> 
> > The i3c bus spec define a bus configuration where the i2c devices
> 
> 		   ^defines			    I2C devices...
> 
> > doesn't have the 50ns filter yet they allow the SDR max speed.
> 
>   ^don't	^ a 50ns filter but support SCL running at SDR max
> rate (12MHz).
> 
> > 
> > This patch introduce the limited bus mode so the users can use
> 
> 	     ^introduces		    ^ so that users
> 
> > a higher speed on presence of i2c devices index 1.
> 
> 		 ^in
> 
> > 
> > Signed-off-by: Vitor Soares <vitor.soares@...opsys.com>
> > Cc: Boris Brezillon <bbrezillon@...nel.org>
> > Cc: <linux-kernel@...r.kernel.org>
> > ---
> >  drivers/i3c/master.c       | 5 +++++
> >  include/linux/i3c/master.h | 5 +++++
> >  2 files changed, 10 insertions(+)
> > 
> > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > index 1c4a86a..46d3774 100644
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -463,6 +463,7 @@ static int i3c_bus_init(struct i3c_bus *i3cbus)
> >  static const char * const i3c_bus_mode_strings[] = {
> >  	[I3C_BUS_MODE_PURE] = "pure",
> >  	[I3C_BUS_MODE_MIXED_FAST] = "mixed-fast",
> > +	[I3C_BUS_MODE_MIXED_LIMITED] = "mixed-limited",
> >  	[I3C_BUS_MODE_MIXED_SLOW] = "mixed-slow",
> >  };
> >  
> > @@ -575,6 +576,7 @@ int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode,
> >  			i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
> >  		break;
> >  	case I3C_BUS_MODE_MIXED_FAST:
> > +	case I3C_BUS_MODE_MIXED_LIMITED:
> >  		if (!i3cbus->scl_rate.i3c)
> >  			i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
> >  		if (!i3cbus->scl_rate.i2c)
> > @@ -2481,6 +2483,9 @@ int i3c_master_register(struct i3c_master_controller *master,
> >  				mode = I3C_BUS_MODE_MIXED_FAST;
> >  			break;
> >  		case I3C_LVR_I2C_INDEX(1):
> > +			if (mode < I3C_BUS_MODE_MIXED_LIMITED)
> > +				mode = I3C_BUS_MODE_MIXED_LIMITED;
> > +			break;
> >  		case I3C_LVR_I2C_INDEX(2):
> >  			if (mode < I3C_BUS_MODE_MIXED_SLOW)
> >  				mode = I3C_BUS_MODE_MIXED_SLOW;
> > diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> > index 44fb3cf..740235e 100644
> > --- a/include/linux/i3c/master.h
> > +++ b/include/linux/i3c/master.h
> > @@ -250,12 +250,17 @@ struct i3c_device {
> >   *			     the bus. The only impact in this mode is that the
> >   *			     high SCL pulse has to stay below 50ns to trick I2C
> >   *			     devices when transmitting I3C frames
> > + * @I3C_BUS_MODE_MIXED_LIMITED: I2C devices without 50ns spike filter are
> > + *				present on the bus. However they allows
> > + *				compliance up to the maximum SDR SCL clock
> > + *				frequency.
> 
> 						    However they support
> 				SCL clock running at maximum SDR rate
> 				(12.5MHz).
> 
> >   * @I3C_BUS_MODE_MIXED_SLOW: I2C devices without 50ns spike filter are present
> >   *			     on the bus
> >   */
> >  enum i3c_bus_mode {
> >  	I3C_BUS_MODE_PURE,
> >  	I3C_BUS_MODE_MIXED_FAST,
> > +	I3C_BUS_MODE_MIXED_LIMITED,
> >  	I3C_BUS_MODE_MIXED_SLOW,
> >  };
> >  
> 
> The code itself looks good.
> 
> Thanks,
> 
> Boris

Thanks for your feedback I will address the fixes next version.


Best regards,
Vitor Soares