Re: [PATCH 1/2] Bluetooth: btintel: Add platform device for rfkill signal

[Marcel Holtmann <marcel@holtmann.org>]

Hi Chethan,

>>> Driver to add INTL6205 platform ACPI device to enable out
>>> of band GPIO signalling to handle rfkill and reset the
>>> bluetooth controller. Expose an interface in kernel to
>>> assert GPIO signal.
>>> 
>>> Signed-off-by: Chethan T N <chethan.tumkur.narayan@intel.com>
>>> Signed-off-by: Sukumar Ghorai <sukumar.ghorai@intel.com>
>>> Signed-off-by: Raghuram Hegde <raghuram.hegde@intel.com>
>>> ---
>>> drivers/bluetooth/btintel.c | 68 +++++++++++++++++++++++++++++++++++++++++++++
>>> drivers/bluetooth/btintel.h |  6 ++++
>>> 2 files changed, 74 insertions(+)
>>> 
>>> diff --git a/drivers/bluetooth/btintel.c b/drivers/bluetooth/btintel.c
>>> index 5270d5513201..538cd6b6c524 100644
>>> --- a/drivers/bluetooth/btintel.c
>>> +++ b/drivers/bluetooth/btintel.c
>>> @@ -24,6 +24,9 @@
>>> #include <linux/module.h>
>>> #include <linux/firmware.h>
>>> #include <linux/regmap.h>
>>> +#include <linux/acpi.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/gpio/consumer.h>
>>> #include <asm/unaligned.h>
>>> 
>>> #include <net/bluetooth/bluetooth.h>
>>> @@ -375,6 +378,71 @@ int btintel_read_version(struct hci_dev *hdev, struct intel_version *ver)
>>> }
>>> EXPORT_SYMBOL_GPL(btintel_read_version);
>>> 
>>> +static struct gpio_desc *reset_gpio_handler;
>> 
>> this thing is so inherent broken. Please never ever do that. If there are two reset handlers or two Intel USB devices connected things will go horrible wrong.
> Is it fine to keep list of the descriptors handlers for all the Intel
> devices connected?
>> 
>>> +void btintel_reset_bt(struct hci_dev *hdev, unsigned char code)
>>> +{
>>> +     if (!reset_gpio_handler)
>>> +             return;
>>> +
>>> +     gpiod_set_value(reset_gpio_handler, 0);
>>> +     mdelay(100);
>>> +     gpiod_set_value(reset_gpio_handler, 1);
>>> +}
>>> +EXPORT_SYMBOL_GPL(btintel_reset_bt);
>> 
>> What happens here when you do this? Does the Bluetooth USB device disconnect from the USB bus and gets re-enumerated and the btusb_probe() routine gets called again?
> Yes, USB re-enumeration will be done and btusb_proble() function will be called.

As I said, in that case it is fine to implement this an RFKILL switch. It is platform RFKILL switch. The USB device actually gets virtually disconnected.

>> 
>> If this is the case, then I have no idea how many times I have to explain. It is a platfrom reset switch and using RFKILL for this is acceptable.
> Thought of make this platform independent by exposing ACPI object
> "INTL6205", by doing so in case different platforms if the ACPI object
> is exposed by the platform then this driver would be loaded.
> Kindly please do suggest.

See above. I really don't know what else to say. You can not handle this inside hci_dev since the hci_dev will be actually destroyed if you pull the GPIO.

>> 
>>> +
>>> +static const struct acpi_gpio_params reset_gpios = { 0, 0, false };
>>> +static const struct acpi_gpio_mapping acpi_btintel_gpios[] = {
>>> +     { "reset-gpios", &reset_gpios, 1 },
>>> +     { },
>>> +};
>>> +
>>> +static int btintel_probe(struct platform_device *pdev)
>>> +{
>>> +     struct device *hdev;
>>> +
>>> +     hdev = devm_kzalloc(&pdev->dev, sizeof(*hdev), GFP_KERNEL);
>>> +     if (!hdev)
>>> +             return -ENOMEM;
>> 
>> What is this doing. This makes no sense.
>> 
>>> +
>>> +     if (!ACPI_HANDLE(&pdev->dev))
>>> +             return -ENODEV;
>>> +
>>> +     if (acpi_dev_add_driver_gpios(ACPI_COMPANION(&pdev->dev),
>>> +                                  acpi_btintel_gpios))
>>> +             return -EINVAL;
>>> +
>>> +     reset_gpio_handler = devm_gpiod_get_optional(&pdev->dev,
>>> +                                     "reset", GPIOD_OUT_HIGH);
>>> +     if (IS_ERR(reset_gpio_handler))
>>> +             return PTR_ERR(reset_gpio_handler);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int btintel_remove(struct platform_device *pdev)
>>> +{
>>> +     acpi_dev_remove_driver_gpios(ACPI_COMPANION(&pdev->dev));
>>> +     return 0;
>>> +}
>>> +
>>> +#ifdef CONFIG_ACPI
>>> +static const struct acpi_device_id btintel_acpi_match[] = {
>>> +     { "INTL6205", 0 },
>>> +     { },
>>> +};
>>> +MODULE_DEVICE_TABLE(acpi, btintel_acpi_match);
>>> +#endif
>>> +
>>> +static struct platform_driver btintel_driver = {
>>> +     .probe = btintel_probe,
>>> +     .remove = btintel_remove,
>>> +     .driver = {
>>> +             .name = "btintel",
>>> +             .acpi_match_table = ACPI_PTR(btintel_acpi_match),
>>> +     },
>>> +};
>>> +module_platform_driver(btintel_driver);
>> 
>> I am not convinced this actually works since now we have two module_init and module_exit functions.
> We have tested these changes on two different platform and it is working.

Then bring a second Intel Bluetooth controller into your platform and see what happens. One controller hdev->hw_reset can influence the other?

Regards

Marcel