[RFC v1 7/7] usb: onboard-hub: Add conditional compilation for I2C initialization

[Michal Simek]

On 5/12/25 09:06, Quentin Schulz wrote:
> Hi Anand,
> 
> On 5/9/25 7:45 PM, Anand Moon wrote:
>> Hi Quentin,
>>
>> On Fri, 9 May 2025 at 17:21, Quentin Schulz <quentin.schulz at cherry.de> wrote:
>>>
>>> Hi Neil, Anand,
>>>
>>> On 5/9/25 9:57 AM, Neil Armstrong wrote:
>>>> On 09/05/2025 09:02, Anand Moon wrote:
>>>>> Add conditional compilation for the usb5744_i2c_init() function based
>>>>> on the CONFIG_DM_I2C configuration, to avoid compilation failure.
>>>>>
>>>>>     CC      net/net-common.o
>>>>>     AR      net/built-in.o
>>>>>     LDS     u-boot.lds
>>>>>     LD      u-boot
>>>>> aarch64-linux-gnu-ld.bfd: common/usb_onboard_hub.o: in function
>>>>> `usb5744_i2c_init':
>>>>> /home/amoon/mainline/u-boot/amlogic/u-boot-maineline/common/
>>>>> usb_onboard_hub.c:74:(.text.usb5744_i2c_init+0xfc): undefined
>>>>> reference to `i2c_get_chip'
>>>>> aarch64-linux-gnu-ld.bfd: /home/amoon/mainline/u-boot/amlogic/u-boot-
>>>>> maineline/common/usb_onboard_hub.c:89:(.text.usb5744_i2c_init+0x1a0):
>>>>> undefined reference to `dm_i2c_write'
>>>>> aarch64-linux-gnu-ld.bfd: /home/amoon/mainline/u-boot/amlogic/u-boot-
>>>>> maineline/common/usb_onboard_hub.c:96:(.text.usb5744_i2c_init+0x1c8):
>>>>> undefined reference to `dm_i2c_write'
>>>>> aarch64-linux-gnu-ld.bfd: /home/amoon/mainline/u-boot/amlogic/u-boot-
>>>>> maineline/common/usb_onboard_hub.c:104:(.text.usb5744_i2c_init+0x1f0):
>>>>> undefined reference to `dm_i2c_write'
>>>>> Segmentation fault (core dumped)
>>>>> make: *** [Makefile:1824: u-boot] Error 139
>>>>> make: *** Deleting file 'u-boot'
>>>>>
>>>>> Signed-off-by: Anand Moon <linux.amoon at gmail.com>
>>>>> ---
>>>>>    common/usb_onboard_hub.c | 4 ++++
>>>>>    1 file changed, 4 insertions(+)
>>>>>
>>>>> diff --git a/common/usb_onboard_hub.c b/common/usb_onboard_hub.c
>>>>> index 1242513c631..92e3f3a92c9 100644
>>>>> --- a/common/usb_onboard_hub.c
>>>>> +++ b/common/usb_onboard_hub.c
>>>>> @@ -30,6 +30,7 @@ struct onboard_hub_data {
>>>>>        int (*init)(struct udevice *dev);
>>>>>    };
>>>>> +#if CONFIG_IS_ENABLED(DM_I2C)
>>>>>    static int usb5744_i2c_init(struct udevice *dev)
>>>>>    {
>>>>>        /*
>>>>> @@ -109,6 +110,7 @@ static int usb5744_i2c_init(struct udevice *dev)
>>>>>        return 0;
>>>>>    }
>>>>> +#endif
>>>>>    int usb_onboard_hub_reset(struct udevice *dev)
>>>>>    {
>>>>> @@ -222,7 +224,9 @@ static const struct onboard_hub_data usb2514_data = {
>>>>>    };
>>>>>    static const struct onboard_hub_data usb5744_data = {
>>>>> +#if CONFIG_IS_ENABLED(DM_I2C)
>>>>>        .init = usb5744_i2c_init,
>>>>> +#endif
>>>>>        .power_on_delay_us = 1000,
>>>>>        .reset_us = 5,
>>>>>    };
>>>>
>>>> I think you should completely disable usb5744_data in this case
>>>>
>>>
>>> I would recommend to go the same route as the Linux kernel which has a
>>> special Kconfig option for it, c.f. USB_ONBOARD_DEV_USB5744 which adds
>>> the necessary dependencies.
>>>
>> On Linux kernel, it needs to parse the device node with i2c-bus.
>>
> 
> Seems like it does in U-Boot too? c.f. usb5744_i2c_init() with 
> dev_read_phandle_with_args with i2c-bus?
> 
>>> We probably should be careful and figure out which boards are actually
>>> using the usb5744 and add this symbol to their defconfig so they don't
>>> regress.
>>>
>>  From my initial analysis configs/xilinx_zynqmp_kria_defconfig
>> which use CONFIG_USB_ONBOARD_HUB
>> I believe using DM_I2C to guard the code is the best approach.
>> it should be around .init() callback to guard this to work.
>>
> 
> I disagree. The driver clearly supports the USB5744 and the driver is compiled 
> regardless of DM_I2C support which is required (as far as I understood, maybe 
> that's incorrect?) for being able to use USB5744? I don't like hidden dependencies.
> 
> Also, I believe Neil's point is we shouldn't try to probe the USB5744 if there 
> is no DM_I2C support, simply excluding .init() callback will probably just 
> render this "support" of USB5744 non-functional?

USB5744 can be configured differently. We are using two configurations.
1. no initialization over i2c
(but still you can have a need to have driver for reset or power)
2. initialization over i2c to start the hub

And there is also one more configuration via SPI.

It means I don't think DM_I2C should be real dependency on getting usb5744 to 
operate.

Thanks,
Michal