linux-kernel - Re: [PATCH v1 3/4] serial: qcom-geni: Enable PM runtime for serial driver

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Message-ID: <2zeqt3tu36qcxs6xrzqqmn3ssmyzetl6tq6lxrjdvt5dhxrtv4@g5q4zhk4sebs>
Date: Tue, 30 Dec 2025 20:23:58 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Praveen Talari <praveen.talari@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-serial@...r.kernel.org, alexey.klimov@...aro.org,
        krzk@...nel.org, bryan.odonoghue@...aro.org,
        jorge.ramirez@....qualcomm.com,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>, 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 3/4] serial: qcom-geni: Enable PM runtime for serial
 driver

On Mon, Nov 10, 2025 at 03:40:42PM +0530, Praveen Talari wrote:
> The GENI serial driver currently handles power resource management
> through calls to the statically defined geni_serial_resources_on() and
> geni_serial_resources_off() functions. This approach reduces modularity
> and limits support for platforms with diverse power management
> mechanisms, including resource managed by firmware.
> 
> Improve modularity and enable better integration with platform-specific
> power management, introduce support for runtime PM. Use
> pm_runtime_resume_and_get() and pm_runtime_put_sync() within the
> qcom_geni_serial_pm() callback to control resource power state
> transitions based on UART power state changes.
> 
> Signed-off-by: Praveen Talari <praveen.talari@....qualcomm.com>
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 

This breaks BT support on the Qualcomm RB2 platform. With this patch
applied, I'm getting the following:

root@...m-armv8a:~# dmesg | grep tty\\\|hci0
[    0.000000] Kernel command line:  ignore_loglevel console=ttyMSM0,115200n8 earlycon root=PARTLABEL=rootfs rootwait systemd.mask=pd-mapper.service --   androidboot.bootdevice=4744000.sdhci androidboot.serialno=2b89b520 androidboot.baseband=apq msm_drm.dsi_display0=qcom,mdss_dsi_ext_bridge_1080p:
[    4.074354] 4a8c000.serial: ttyHS1 at MMIO 0x4a8c000 (irq = 140, base_baud = 0) is a MSM
[    4.099410] serial serial0: tty port ttyHS1 registered
[    4.131200] Bluetooth: hci0: setting up wcn399x
[    4.149847] 4a90000.serial: ttyMSM0 at MMIO 0x4a90000 (irq = 142, base_baud = 0) is a MSM
[    4.229099] printk: legacy console [ttyMSM0] enabled
[    6.499519] Bluetooth: hci0: command 0xfc00 tx timeout
[    6.514347] Bluetooth: hci0: Reading QCA version information failed (-110)
[    6.559933] Bluetooth: hci0: Retry BT power ON:0
[    8.016330] systemd[1]: Created slice Slice /system/getty.
[    8.066194] systemd[1]: Created slice Slice /system/serial-getty.
[    8.148389] systemd[1]: Expecting device /dev/ttyMSM0...
[    8.956804] Bluetooth: hci0: command 0xfc00 tx timeout
[    8.962447] Bluetooth: hci0: Reading QCA version information failed (-110)
[    8.976917] Bluetooth: hci0: Retry BT power ON:1
[   11.296715] Bluetooth: hci0: command 0xfc00 tx timeout
[   11.302340] Bluetooth: hci0: Reading QCA version information failed (-110)
[   11.309534] Bluetooth: hci0: Retry BT power ON:2
[   13.660078] Bluetooth: hci0: command 0xfc00 tx timeout
[   13.665814] Bluetooth: hci0: Reading QCA version information failed (-110)

After reverting the next and this patches, BT is back to normal:

[    4.067201] 4a8c000.serial: ttyHS1 at MMIO 0x4a8c000 (irq = 140, base_baud = 0) is a MSM
[    4.082426] serial serial0: tty port ttyHS1 registered
[    4.106122] 4a90000.serial: ttyMSM0 at MMIO 0x4a90000 (irq = 142, base_baud = 0) is a MSM
[    4.108647] Bluetooth: hci0: setting up wcn399x
[    4.125371] printk: legacy console [ttyMSM0] enabled
[    4.445205] Bluetooth: hci0: QCA Product ID   :0x0000000a
[    4.450927] Bluetooth: hci0: QCA SOC Version  :0x40020150
[    4.456470] Bluetooth: hci0: QCA ROM Version  :0x00000201
[    4.462006] Bluetooth: hci0: QCA Patch Version:0x00000001
[    4.509408] Bluetooth: hci0: QCA controller version 0x01500201
[    4.515656] Bluetooth: hci0: QCA Downloading qca/apbtfw11.tlv
[    5.488739] Bluetooth: hci0: QCA Downloading qca/apnv11.bin
[    5.671740] Bluetooth: hci0: QCA setup on UART is completed
[    7.993368] systemd[1]: Created slice Slice /system/getty.
[    8.045612] systemd[1]: Created slice Slice /system/serial-getty.
[    8.125418] systemd[1]: Expecting device /dev/ttyMSM0...


-- 
With best wishes
Dmitry