lkml.org 
[lkml]   [2019]   [Apr]   [16]   [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
Hi Boris,

From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Tue, Apr 16, 2019 at 06:50:41

> On Mon, 15 Apr 2019 20:46:41 +0200
> Vitor Soares <vitor.soares@synopsys.com> wrote:
>
> > Currently in case of mixed slow bus topologie and all i2c devices
> > support FM+ speed, the i3c subsystem limite the SCL to FM speed.
>

I will it replace with your message below.

> "
> Currently the I3C framework limits SCL frequency to FM speed when
> dealing with a mixed slow bus, even if all I2C devices are FM+ capable.
> "
>
> > Also in case on mixed slow bus mode the max speed for both
> > i2c or i3c transfers is FM or FM+.
>
> Looks like you're basically repeating what you said above.

What I meant was that I3C framework isn't limiting the I3C speed in case
of mixed slow bus.

>
> >
> > This patch fix the definition of i2c and i3c scl rate based on bus
>
> ^fixes on the bus
>
> > topologie and LVR[4] if no user input.
>
> ^topology ^if the rate is not already specified by the user.
>
> > In case of mixed slow mode the i3c scl rate is overridden.
>
> ^ with the max
> I2C rate.
>
> >
> > Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure")
> > Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
> > Cc: Boris Brezillon <bbrezillon@kernel.org>
> > Cc: <stable@vger.kernel.org>
> > Cc: <linux-kernel@vger.kernel.org>
> > ---
> > drivers/i3c/master.c | 39 +++++++++++++++++++++++++--------------
> > 1 file changed, 25 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > index 909c2ad..1c4a86a 100644
> > --- a/drivers/i3c/master.c
> > +++ b/drivers/i3c/master.c
> > @@ -564,20 +564,30 @@ static const struct device_type i3c_masterdev_type = {
> > .groups = i3c_masterdev_groups,
> > };
> >
> > -int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode)
> > +int i3c_bus_set_mode(struct i3c_bus *i3cbus, enum i3c_bus_mode mode,
> > + unsigned long i2c_scl_rate)
>
>
> Can we rename the last arg into max_i2c_scl_rate?

The i2c_scl_rate is base on LVR[4] bit and the user can set a higher scl
rate, this is reason I didn't named it to max_i2c_scl_rate.
But if you think that make more sense I'm ok with that.

>
> > {
> > 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.

>
> The patch looks good otherwise.

Thanks.

>
> > + break;
> > + default:
> > + return -EINVAL;
> > }
> > -
> > /*
> > * I3C/I2C frequency may have been overridden, check that user-provided
> > * values are not exceeding max possible frequency.
> > @@ -1980,9 +1990,6 @@ of_i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
> > /* LVR is encoded in reg[2]. */
> > boardinfo->lvr = reg[2];
> >
> > - if (boardinfo->lvr & I3C_LVR_I2C_FM_MODE)
> > - master->bus.scl_rate.i2c = I3C_BUS_I2C_FM_SCL_RATE;
> > -
> > list_add_tail(&boardinfo->node, &master->boardinfo.i2c);
> > of_node_get(node);
> >
> > @@ -2432,6 +2439,7 @@ int i3c_master_register(struct i3c_master_controller *master,
> > const struct i3c_master_controller_ops *ops,
> > bool secondary)
> > {
> > + unsigned long i2c_scl_rate = I3C_BUS_I2C_FM_PLUS_SCL_RATE;
> > struct i3c_bus *i3cbus = i3c_master_get_bus(master);
> > enum i3c_bus_mode mode = I3C_BUS_MODE_PURE;
> > struct i2c_dev_boardinfo *i2cbi;
> > @@ -2481,9 +2489,12 @@ int i3c_master_register(struct i3c_master_controller *master,
> > ret = -EINVAL;
> > goto err_put_dev;
> > }
> > +
> > + if (i2cbi->lvr & I3C_LVR_I2C_FM_MODE)
> > + i2c_scl_rate = I3C_BUS_I2C_FM_SCL_RATE;
> > }
> >
> > - ret = i3c_bus_set_mode(i3cbus, mode);
> > + ret = i3c_bus_set_mode(i3cbus, mode, i2c_scl_rate);
> > if (ret)
> > goto err_put_dev;
> >

Best regards,
Vitor Soares

\
 
 \ /
  Last update: 2019-04-16 16:26    [W:0.140 / U:2.612 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site