[U-Boot] [PATCH 3/4] i2c: dm: Record maximum id of devices before probing devices

[Simon Glass]

Hi Michal,

On Thu, 31 Jan 2019 at 04:03, Michal Simek <michal.simek at xilinx.com> wrote:
>
> On 31. 01. 19 11:04, Simon Glass wrote:
> > Hi Michal,
> >
> > On Fri, 18 Jan 2019 at 08:13, Michal Simek <michal.simek at xilinx.com>
wrote:
> >>
> >> There is a need to find out the first free i2c ID which can be used for
> >> i2s buses (including i2c buses connected to i2c mux). Do it early in
> >> init and share this variable with other i2c classes for uniq bus
> >> identification.
> >>
> >> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> >> ---
> >>
> >>  drivers/i2c/i2c-uclass.c | 19 +++++++++++++++++++
> >>  include/i2c.h            |  3 +++
> >>  2 files changed, 22 insertions(+)
> >>
> >> diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
> >> index 975318e5f254..aaece115f02f 100644
> >> --- a/drivers/i2c/i2c-uclass.c
> >> +++ b/drivers/i2c/i2c-uclass.c
> >> @@ -23,6 +23,8 @@ enum {
> >>         PIN_COUNT,
> >>  };
> >>
> >> +int i2c_highest_id = -1;
> >> +
> >>  /* Useful debugging function */
> >>  void i2c_dump_msgs(struct i2c_msg *msg, int nmsgs)
> >>  {
> >> @@ -619,10 +621,27 @@ static int i2c_child_post_bind(struct udevice
*dev)
> >>  #endif
> >>  }
> >>
> >> +int i2c_uclass_init(struct uclass *class)
> >> +{
> >> +#ifdef CONFIG_OF_LIVE
> >> +       int ret;
> >> +
> >> +       ret = of_alias_get_highest_id("i2c");
> >> +       if (ret >= 0)
> >> +               i2c_highest_id = ret;
> >> +#else
> >> +       i2c_highest_id = fdtdec_get_alias_highest_id(gd->fdt_blob,
"i2c");
> >> +#endif
> >
> > This should call dev_read_alias_highest_id() or similar, which does
> > the logic you have here.
>
> not a problem with this.
>
> >
> >> +       debug("%s: i2c highest_id %d\n", __func__, i2c_highest_id);
> >> +
> >> +       return 0;
> >> +}
> >> +
> >>  UCLASS_DRIVER(i2c) = {
> >>         .id             = UCLASS_I2C,
> >>         .name           = "i2c",
> >>         .flags          = DM_UC_FLAG_SEQ_ALIAS,
> >> +       .init           = i2c_uclass_init,
> >>  #if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA)
> >>         .post_bind      = dm_scan_fdt_dev,
> >>  #endif
> >> diff --git a/include/i2c.h b/include/i2c.h
> >> index ccffc1955275..c69e26deaeed 100644
> >> --- a/include/i2c.h
> >> +++ b/include/i2c.h
> >> @@ -16,6 +16,9 @@
> >>  #ifndef _I2C_H_
> >>  #define _I2C_H_
> >>
> >> +/* Stores maximum highest i2c alias number */
> >> +extern int i2c_highest_id;
> >
> > This should be in uclass-private data, not a global.
>
> In this case there are two uclasses. UCLASS_I2C and UCLASS_I2C_MUX which
> has to share the same numbers. I would expect that private data will be
> private just for one not for both.
> Reading

Hmm I hadn't realised that. Perhaps you can wrap it in a function which
looks up the I2C uclass and the private data. We should try to avoid using
BSS so that I2C can be used before relocation, etc.

>
> >
> > But also I feel that the behaviour needs to be consistent for all
> > U-Boot buses, not just I2C. So can we modify the existing core DM code
> > instead? I think a change to uclass_resolve_seq() might be enough.
>
> I need to check calling sequence to see if this is properly timed or not.

OK.

Regards,
Simon