lkml.org 
[lkml]   [2019]   [Apr]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 1/3] i3c: fix i2c and i3c scl rate by bus mode
Date
From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Mon, Apr 22, 2019 at 17:07:15

> On Mon, 22 Apr 2019 15:54:33 +0000
> Vitor Soares <Vitor.Soares@synopsys.com> wrote:
>
>
> > > > >
> > > > > > {
> > > > > > i3cbus->mode = mode;
> > > > > >
> > > > > > - if (!i3cbus->scl_rate.i3c)
> > > > > > - i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
> > > > > > -
> > > > > > - if (!i3cbus->scl_rate.i2c) {
> > > > > > - if (i3cbus->mode == I3C_BUS_MODE_MIXED_SLOW)
> > > > > > - i3cbus->scl_rate.i2c = I3C_BUS_I2C_FM_SCL_RATE;
> > > > > > - else
> > > > > > - i3cbus->scl_rate.i2c = I3C_BUS_I2C_FM_PLUS_SCL_RATE;
> > > > > > + switch (i3cbus->mode) {
> > > > > > + case I3C_BUS_MODE_PURE:
> > > > > > + if (!i3cbus->scl_rate.i3c)
> > > > > > + i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
> > > > > > + break;
> > > > > > + case I3C_BUS_MODE_MIXED_FAST:
> > > > > > + if (!i3cbus->scl_rate.i3c)
> > > > > > + i3cbus->scl_rate.i3c = I3C_BUS_TYP_I3C_SCL_RATE;
> > > > > > + if (!i3cbus->scl_rate.i2c)
> > > > > > + i3cbus->scl_rate.i2c = i2c_scl_rate;
> > > > > > + break;
> > > > > > + case I3C_BUS_MODE_MIXED_SLOW:
> > > > > > + if (!i3cbus->scl_rate.i2c)
> > > > > > + i3cbus->scl_rate.i2c = i2c_scl_rate;
> > > > > > + i3cbus->scl_rate.i3c = i3cbus->scl_rate.i2c;
> > > > >
> > > > > Maybe we should do
> > > > >
> > > > > if (!i3cbus->scl_rate.i3c ||
> > > > > i3cbus->scl_rate.i3c > i3cbus->scl_rate.i2c)
> > > > > i3cbus->scl_rate.i3c = i3cbus->scl_rate.i2c;
> > > > >
> > > > > Just in case the I3C rate forced by the user is lower than the max I2C
> > > > > rate.
> > > >
> > > > That was something that I considered but TBH it isn't a real use case.
> > >
> > > Add a WARN_ON() to at least catch such inconsistencies. And maybe we
> > > should add a dev_warn() when the user-defined rates do not match
> > > the mode/LVR constraints. It's easy to do a mistake when writing a dts.
> >
> > I think the WARN_ON() is too evasive on the screen and won't provide the
> > information we want.
> > The dev_warn() should work perfectly here.
> >
> > if (i3cbus->scl_rate.i3c < i3cbus->scl_rate.i2c)
> > dev_warn(&i3cbus->cur_master->dev->dev,
> > "%s: i3c-scl-hz lower then i2c-scl-hz\n", __func__);
>
> Using dev_warn() sounds good, though I don't think you need the
> __func__ here. Also, please print the i2c/i3c rates in the message, and
> align the second line on the open parens.
>
> > if (i3cbus->scl_rate.i2c != I3C_BUS_I2C_FM_SCL_RATE ||
> > i3cbus->scl_rate.i2c != I3C_BUS_I2C_FM_PLUS_SCL_RATE)
> > dev_warn(&i3cbus->cur_master->dev->dev,
> > "%s: i2c-scl-hz not defined according MIPI I3C spec\n",
> > __func__);
>
> Is that really a problem? Having an i2c rate that is less than FM speed
> sounds like a valid case to me.

I'm addressing the spec constrains.

In the practice it can be SM or even HS, it depends on the interface.

>
> >
> > Maybe it make more sense to do this check on of_populate_i3c_bus(), what
> > do you think?
> >
>
> No, we really want to have this check here, because we might support
> other HW description formats at some point (board-files, ACPI, ...).

Yes, you are right. I forgot that point.

\
 
 \ /
  Last update: 2019-04-22 20:02    [W:0.065 / U:0.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site