linux-kernel - Re: [PATCH v1] serial: qcom_geni: Fix BT failure regression on RB2 platform

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Message-ID: <vapb2r5xbrchobhtvwr43wdqbtd2pzxkfhiyzltipvpdkmaqyj@zkabog4sf4g3>
Date: Wed, 7 Jan 2026 18:13:26 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Praveen Talari <praveen.talari@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....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, andersson@...nel.org, 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 v1] serial: qcom_geni: Fix BT failure regression on RB2
 platform

On Wed, Jan 07, 2026 at 07:38:10PM +0530, Praveen Talari wrote:
> Hi Dmistry,
> 
> On 1/7/2026 5:05 PM, Dmitry Baryshkov wrote:
> > On Wed, Jan 07, 2026 at 04:28:22PM +0530, Praveen Talari wrote:
> > > Hi Konrad,
> > > 
> > > On 1/7/2026 4:16 PM, Konrad Dybcio wrote:
> > > > On 1/7/26 10:24 AM, Praveen Talari wrote:
> > > > > Hi
> > > > > 
> > > > > On 1/7/2026 12:52 PM, Dmitry Baryshkov wrote:
> > > > > > On Wed, 7 Jan 2026 at 09:06, Praveen Talari
> > > > > > <praveen.talari@....qualcomm.com> wrote:
> > > > > > > 
> > > > > > > Hi Dmistry,
> > > > > > > 
> > > > > > > On 1/7/2026 12:24 PM, Dmitry Baryshkov wrote:
> > > > > > > > On Wed, 7 Jan 2026 at 08:48, Praveen Talari
> > > > > > > > <praveen.talari@....qualcomm.com> wrote:
> > > > > > > > > 
> > > > > > > > > A regression in linux-next causes Bluetooth functionality to fail during
> > > > > > > > 
> > > > > > > > linux-next is an ephemeral thing. Please reference the exact commit.
> > > > > > > > 
> > > > > > > > > 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 their default state.
> > > > > > > > > When wakeup IRQ registration happens afterward, it conflicts with these
> > > > > > > > > GPIO settings, causing state corruption that breaks Bluetooth
> > > > > > > > > functionality.
> > > > > > > > 
> > > > > > > > How does it "conflict with GPIO settings", what is "state corruption"?
> > > > > > > 
> > > > > > > I mean the issue occurs because the GPIO state is being altered during
> > > > > > > the wakeup source registration process..
> > > > > > 
> > > > > > Altered how?
> > > > > 
> > > > > During the runtime resume of devices, GPIOs are configured to QUP mode. However, when registering the wakeup IRQ using dev_pm_set_dedicated_wake_irq(), these GPIOs are reset back to FUNC mode, which impacts the RX GPIO and leads to Bluetooth failures
> > > > 
> > > > "QUP mode" and "FUNC mode" are tough to swallow even for an insider.. How
> > > > about:
> > > > 
> > > > "qup_x" and "gpio" pinmux functions
> > > 
> > > Yes, you are right. I am talking about "qup_x" and "gpio" pinmux functions
> > 
> > => commit message, please.
> 
> I hope the commit text below should be appropriate
> 
> serial: qcom-geni: Fix BT failure regression on RB2 platform
> 
> A regression in 6.19-rc1 causes Bluetooth functionality to fail during

Commit abcdefaa ("Foo Bar baz") caused BT init to fail....

Otherwise LGTM.

> 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.
> 
> Thanks,
> Praveen
> 
> > 
> > > 
> > > Thanks,
> > > Praveen Talari
> > > > 
> > > > ?
> > > > 
> > > > Konrad
> > > 
> > 
> 

-- 
With best wishes
Dmitry