Re: [PATCH 4/7] coresight: tpiu: Move ACPI support from AMBA driver to platform driver

Anshuman Khandual
2023-11-22T07:02:40Z

On 11/15/23 19:23, James Clark wrote:
>
>
> On 27/10/2023 08:29, Anshuman Khandual wrote:
>> Add support for the tpiu device in the platform driver, which can then be
>> used on ACPI based platforms. This change would now allow runtime power
>> management for ACPI based systems. The driver would try to enable the APB
>> clock if available.
>>
> [...]
>> +#ifdef CONFIG_ACPI
>> +static const struct acpi_device_id tpiu_acpi_ids[] = {
>> + {"ARMHC979", 0}, /* ARM CoreSight TPIU */
>> + {}
>> +};
>> +MODULE_DEVICE_TABLE(acpi, tpiu_acpi_ids);
>> +#endif
>> +
>> +static struct platform_driver tpiu_platform_driver = {
>> + .probe = tpiu_platform_probe,
>> + .remove = tpiu_platform_remove,
>> + .driver = {
>> + .name = "coresight-tpiu-platform",
>> + .acpi_match_table = ACPI_PTR(tpiu_acpi_ids),
>> + .suppress_bind_attrs = true,
>> + .pm = &tpiu_dev_pm_ops,
>> + },
>> +};
>> +module_platform_driver(tpiu_platform_driver);
>> +
>
> Is there a special build config where this works? I get an error here

I have been testing this with a config known to work on RB5 board.

> because module_platform_driver() redefines things that are in
> module_amba_driver() which is defined above:
>
> module_amba_driver(tpiu_driver);
>
> This isn't a W=1 build or anything, just a normal one. And it applies to
> most of the patches in this set.

You are right, I am able to recreate this problem with defconfig on
6.7-rc2 as well. The problem here seems to be caused by having both
module_amba_driver() and module_platform_driver() in the same file.

#define module_amba_driver(__amba_drv) \
module_driver(__amba_drv, amba_driver_register, amba_driver_unregister)

#define module_platform_driver(__platform_driver) \
module_driver(__platform_driver, platform_driver_register, \
platform_driver_unregister)

Although, AFAICT, have not seen these before - even on the defconfig.
Just to work around this problem, there can be a common module_init()
/module_exit() to register/unregister both AMBA and platform drivers,
similar to etm4x_init()/etm4x_exit() setup in coresight-etm4x-core.c.