linux-kernel - Re: [PATCH v2] serial: qcom_geni: Fix BT failure regression on RB2 platform

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Message-ID: <1260b788-3156-4116-8683-7e2c46bdafcd@oss.qualcomm.com>
Date: Thu, 8 Jan 2026 09:14:12 +0530
From: Praveen Talari <praveen.talari@....qualcomm.com>
To: Mayank Rana <mayank.rana@....qualcomm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        bryan.odonoghue@...aro.org, dmitry.baryshkov@....qualcomm.com,
        andersson@...nel.org
Cc: psodagud@...cinc.com, djaggi@...cinc.com, quic_msavaliy@...cinc.com,
        quic_vtanuku@...cinc.com, quic_arandive@...cinc.com,
        quic_shazhuss@...cinc.com, quic_cchiluve@...cinc.com
Subject: Re: [PATCH v2] serial: qcom_geni: Fix BT failure regression on RB2
 platform

Hi Mayank,

Thank you for the review.

On 1/8/2026 3:09 AM, Mayank Rana wrote:
> 
> 
> On 1/7/2026 8:26 AM, Praveen Talari wrote:
>> Commit 10904d725f6e ("serial: qcom-geni: Enable PM runtime for serial
>> driver") caused BT init to fail during bootup on the RB2 platform,
>> preventing proper BT initialization. However, BT works correctly after
>> bootup completes.
>>
>> The issue occurs when runtime PM is enabled and uart_add_one_port() is
>> called before wakeup IRQ setup. The uart_add_one_port() call activates
>> the device through runtime PM, which configures GPIOs to the "qup_x"
>> pinmux function during runtime resume. When wakeup IRQ registration
>> happens afterward using dev_pm_set_dedicated_wake_irq(), these GPIOs
>> are reset back to the "gpio" pinmux function, which impacts the RX GPIO
>> and leads to Bluetooth failures.
>>
>> Fix this by ensuring wakeup IRQ setup is completed before calling
>> uart_add_one_port() to prevent the pinmux function conflict.
>>
>> Tested-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>> Reported-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>> Closes: https://lore.kernel.org/all/20251110101043.2108414-4- 
>> praveen.talari@....qualcomm.com/
>> Fixes: 10904d725f6e ("serial: qcom-geni: Enable PM runtime for serial 
>> driver")
>> Signed-off-by: Praveen Talari <praveen.talari@....qualcomm.com>
>> ---
>> v1 -> v2
>> - Updated commit text.
>> - Added Tested-by in commit text
>> ---
>>   drivers/tty/serial/qcom_geni_serial.c | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/ 
>> serial/qcom_geni_serial.c
>> index 6ce6528f5c10..46a9c71630d5 100644
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -1888,12 +1888,6 @@ static int qcom_geni_serial_probe(struct 
>> platform_device *pdev)
>>       if (ret)
>>           goto error;
>> -    devm_pm_runtime_enable(port->se.dev);
>> -
>> -    ret = uart_add_one_port(drv, uport);
>> -    if (ret)
>> -        goto error;
>> -
>>       if (port->wakeup_irq > 0) {
>>           device_init_wakeup(&pdev->dev, true);
>>           ret = dev_pm_set_dedicated_wake_irq(&pdev->dev,
> 
> do you need to handle error handling part here as calling 
> uart_remove_one_port() shall result into NULL access related crash while 
> accessing port->port_dev as port_dev is not allocated 
> (serial_base_port_add() add is not being called due to moving 
> uart_add_one_port() later)

Yes, you are correct. Will address it in next patch.

Thanks,
Praveen Talari

> 
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -1901,7 +1901,6 @@ static int qcom_geni_serial_probe(struct 
> platform_device *pdev)
>                  if (ret) {
>                          device_init_wakeup(&pdev->dev, false);
>                          ida_free(&port_ida, uport->line);
> -                       uart_remove_one_port(drv, uport);
>                          goto error;
>                  }
>          }
> 
>> @@ -1906,6 +1900,12 @@ static int qcom_geni_serial_probe(struct 
>> platform_device *pdev)
>>           }
>>       }
>> +    devm_pm_runtime_enable(port->se.dev);
>> +
>> +    ret = uart_add_one_port(drv, uport);
>> +    if (ret)
>> +        goto error;
>> +
>>       return 0;
>>   error:
>>
>> base-commit: 6cd6c12031130a349a098dbeb19d8c3070d2dfbe
> Regards,
> Mayank