Calling i2c set speed twice for i2c_mux_bus

[Michal Simek]

On 07. 05. 20 12:02, Heiko Schocher wrote:
> Hello Michal,
> 
> Am 07.05.2020 um 10:18 schrieb Michal Simek:
>> On 06. 05. 20 16:47, Simon Glass wrote:
>>> Hi Michal,
>>>
>>> On Tue, 5 May 2020 at 21:43, Simon Glass <sjg at chromium.org> wrote:
>>>>
>>>> Hi Michal,
>>>>
>>>> On Tue, 5 May 2020 at 02:26, Michal Simek <michal.simek at xilinx.com>
>>>> wrote:
>>>>>
>>>>> On 15. 04. 20 8:40, Michal Simek wrote:
>>>>>> On 10. 04. 20 10:49, Heiko Schocher wrote:
>>>>>>> Hello Michal,
>>>>>>>
>>>>>>> Am 10.04.2020 um 08:46 schrieb Michal Simek:
>>>>>>>> Hi Heiko,
>>>>>>>>
>>>>>>>> On 10. 04. 20 7:11, Heiko Schocher wrote:
>>>>>>>>> Hello Michal,
>>>>>>>>>
>>>>>>>>> Am 09.04.2020 um 16:03 schrieb Michal Simek:
>>>>>>>>>> Hi Heiko and Simon,
>>>>>>>>>>
>>>>>>>>>> I have find out one bug in i2c class. I am using zcu104 revC
>>>>>>>>>> board
>>>>>>>>>> which
>>>>>>>>>> has dts in mainline where i2c1 has i2c mux with some channels.
>>>>>>>>>> In DT clock-frequency = <400000>; is specified and it is read in
>>>>>>>>>> i2c_post_probe(). But i2c_mux_bus_drv is also UCLASS_I2C which
>>>>>>>>>> means
>>>>>>>>>> that post probe is called for it too. And because clock-frequency
>>>>>>>>>> property is not there default 100k is used.
>>>>>>>>>>
>>>>>>>>>> I think that is bug and should be fixed.
>>>>>>>>>> Heiko: Are you aware about this issue?
>>>>>>>>>
>>>>>>>>> No :-(
>>>>>>>>>
>>>>>>>>> The question is, is this a bug?
>>>>>>>>
>>>>>>>> I have never seen clock-frequency property in i2c mux bus node.
>>>>>>>> Also I
>>>>>>>> have looked at linux dt binding docs and nothing like that is
>>>>>>>> specified
>>>>>>>> there. From quick look also pca954x driver is not reading it.
>>>>>>>
>>>>>>> Indeed.
>>>>>>>
>>>>>>>>> Should a i2c bus behind a mux not be able to set his own speed?
>>>>>>>>
>>>>>>>> Not sure if that make sense but Linux will likely ignore it. I
>>>>>>>> am not
>>>>>>>> saying it doesn't make sense but I haven't seen this feature.
>>>>>>>
>>>>>>> Ok.
>>>>>>>
>>>>>>>>> But may as a feature (or bugfix?) if "clock-frequency" is not
>>>>>>>>> there,
>>>>>>>>> use the speed of the parent bus...?
>>>>>>>>
>>>>>>>> I was thinking about this too.
>>>>>>>> just c&p quick implementation would look like this. Because it is
>>>>>>>> i2c->i2c_mux->i2c. But maybe there is a better way how to do it.
>>>>>>>>
>>>>>>>> diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c
>>>>>>>> index 2aa3efe8aaa0..982c467deba3 100644
>>>>>>>> --- a/drivers/i2c/i2c-uclass.c
>>>>>>>> +++ b/drivers/i2c/i2c-uclass.c
>>>>>>>> @@ -640,9 +640,21 @@ static int i2c_post_probe(struct udevice *dev)
>>>>>>>>    {
>>>>>>>>    #if CONFIG_IS_ENABLED(OF_CONTROL) &&
>>>>>>>> !CONFIG_IS_ENABLED(OF_PLATDATA)
>>>>>>>>           struct dm_i2c_bus *i2c = dev_get_uclass_priv(dev);
>>>>>>>> +       int parent_speed = I2C_SPEED_STANDARD_RATE;
>>>>>>>> +
>>>>>>>> +       if (dev->parent &&
>>>>>>>> +           device_get_uclass_id(dev->parent) == UCLASS_I2C_MUX &&
>>>>>>>> +           dev->parent->parent &&
>>>>>>>> +           device_get_uclass_id(dev->parent->parent) ==
>>>>>>>> UCLASS_I2C) {
>>>>>>>> +               struct dm_i2c_bus *i2c_parent;
>>>>>>>> +
>>>>>>>> +               i2c_parent =
>>>>>>>> dev_get_uclass_priv(dev->parent->parent);
>>>>>>>> +               parent_speed = i2c_parent->speed_hz;
>>>>>>>> +               /* Not sure if make sense to check that
>>>>>>>> parent_speed is
>>>>>>>> not 0 */
>>>>>>>
>>>>>>> I think this check is not needed.
>>>>>>>
>>>>>>>> +       }
>>>>>>>>
>>>>>>>>           i2c->speed_hz = dev_read_u32_default(dev,
>>>>>>>> "clock-frequency",
>>>>>>>> -                                           
>>>>>>>> I2C_SPEED_STANDARD_RATE);
>>>>>>>> +                                            parent_speed);
>>>>>>>
>>>>>>> Wow, a big if ... may this is clearer (not compile tested)?
>>>>>>>
>>>>>>> udevice *parent = dev_get_parent(dev);
>>>>>>>
>>>>>>> if (parent && device_get_uclass_id(parent) == UCLASS_I2C_MUX) {
>>>>>>>      udevice *parent2 = dev_get_parent(parent);
>>>>>>>      if (parent2 && device_get_uclass_id(parent2) == UCLASS_I2C) {
>>>>>>>          struct dm_i2c_bus *i2cp = dev_get_uclass_priv(parent2);
>>>>>>>
>>>>>>>          parent_speed = i2cp->speed_hz;
>>>>>>>      }
>>>>>>> }
>>>>>>>
>>>>>>> but Simon has a deeper DM knowledge, may there is a better approach.
>>>>>>
>>>>>> Simon: any comment on this one?
>>>>>
>>>>> Simon: Can you please comment this?
>>>>>
>>>>
>>>> OK will take a look.
>>>
>>> I wonder if i2c-mux-uclass.c should define a new uclass for muxed I2C
>>> buses, something like UCLASS_I2C_MUXED_BUS? Then you can define the
>>> behaviour correctly in i2c-mux-uclass.c.
>>>
>>> An I2C controller is not the same as a muxed bus and perhaps we should
>>> be explicitly about the differences. It probably just needs changes to
>>> the mux uclass.
>>
>> Definitely there need to be some changes in connection to i2c muxes. I
>> am aware also about bad behavior when you detect devices.
>> Just look at log below and you will see that devices on base i2c bus are
>> copied also to subbus (especially listing i2c-mux again looks weird).
> 
> Yes, this look like we need here a seperate uclass to handle this
> correct...

Are you going to invest to your time to create?

Thanks,
Michal