linux-kernel - RE: [PATCH] serial: qcom_geni_serial: Setup serial port after Deep sleep

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Date:   Fri, 2 Jun 2023 06:39:02 +0000
From:   "Mehul Raninga (Temp) (QUIC)" <quic_mraninga@...cinc.com>
To:     Bjorn Andersson <andersson@...nel.org>,
        "Mehul Raninga (Temp) (QUIC)" <quic_mraninga@...cinc.com>
CC:     "agross@...nel.org" <agross@...nel.org>,
        "konrad.dybcio@...aro.org" <konrad.dybcio@...aro.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Viken Dadhaniya (QUIC)" <quic_vdadhani@...cinc.com>,
        "Visweswara Tanuku (QUIC)" <quic_vtanuku@...cinc.com>,
        "Vijaya Krishna Nivarthi (Temp) (QUIC)" <quic_vnivarth@...cinc.com>
Subject: RE: [PATCH] serial: qcom_geni_serial: Setup serial port after Deep
 sleep

Hello Andersson,
Thanks for the review. Kindly find my reply inline below.

> -----Original Message-----
> From: Bjorn Andersson <andersson@...nel.org>
> Sent: Thursday, June 1, 2023 9:38 AM
> To: Mehul Raninga (Temp) (QUIC) <quic_mraninga@...cinc.com>
> Cc: agross@...nel.org; konrad.dybcio@...aro.org;
> gregkh@...uxfoundation.org; jirislaby@...nel.org; linux-arm-
> msm@...r.kernel.org; linux-serial@...r.kernel.org; linux-
> kernel@...r.kernel.org; Viken Dadhaniya (QUIC)
> <quic_vdadhani@...cinc.com>; Visweswara Tanuku (QUIC)
> <quic_vtanuku@...cinc.com>; Vijaya Krishna Nivarthi (Temp) (QUIC)
> <quic_vnivarth@...cinc.com>
> Subject: Re: [PATCH] serial: qcom_geni_serial: Setup serial port after Deep
> sleep
> 
> WARNING: This email originated from outside of Qualcomm. Please be
> wary of any links or attachments, and do not enable macros.
> 
> On Wed, May 31, 2023 at 01:06:22PM +0000, Mehul Raninga (Temp)
> (QUIC) wrote:
> > Hello Andersson,
> > Thanks for the review. Kindly find my reply inline below
> >
> > > -----Original Message-----
> > > From: Bjorn Andersson <andersson@...nel.org>
> > > Sent: Tuesday, May 30, 2023 8:37 PM
> > > To: Mehul Raninga (Temp) (QUIC) <quic_mraninga@...cinc.com>
> > > Cc: agross@...nel.org; konrad.dybcio@...aro.org;
> > > gregkh@...uxfoundation.org; jirislaby@...nel.org;
> > > linux-arm-msm@...r.kernel.org; linux- serial@...r.kernel.org;
> > > linux-kernel@...r.kernel.org; Viken Dadhaniya (QUIC)
> > > <quic_vdadhani@...cinc.com>; Visweswara Tanuku (QUIC)
> > > <quic_vtanuku@...cinc.com>; Vijaya Krishna Nivarthi (Temp) (QUIC)
> > > <quic_vnivarth@...cinc.com>
> > > Subject: Re: [PATCH] serial: qcom_geni_serial: Setup serial port
> > > after Deep sleep
> > >
> > > WARNING: This email originated from outside of Qualcomm. Please be
> > > wary of any links or attachments, and do not enable macros.
> > >
> > > On Tue, May 30, 2023 at 04:45:57PM +0530, Mehul Raninga wrote:
> > > > While exiting deep sleep, serial port loses its configuration
> > > > hence it prints garbage characters on console.
> > >
> > > Presumably it lost its configuration sometime after suspend, rather
> > > than while resuming the system?
> >
> > I will reword commit message in V2 as below:
> > Serial port lost its configuration sometime after suspend hence it
> > prints garbage characters on console after resuming.
> 
> Please wrap your replies to 72 chars wide

Noted
> 
> You can probably be more specific than "sometime after suspend" :)

During deepsleep HW configurations are lost, hence it prints garbage
characters on console after resuming.
> 
> > >
> > > >
> > > > Set serial port configuration while resume from deep sleep.
> > > >
> > >
> > > What happens if you do this unconditionally?
> >
> > pm_suspend_via_firmware returns true indicating system is resuming
> > from deepsleep. In case we are not resuming from deepsleep, this
> > serial port setup is not required.
> > >
> > > > Signed-off-by: Mehul Raninga <quic_mraninga@...cinc.com>
> > > > ---
> > > >  drivers/tty/serial/qcom_geni_serial.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/tty/serial/qcom_geni_serial.c
> > > > b/drivers/tty/serial/qcom_geni_serial.c
> > > > index 8582479f0211..c04b8fec30ba 100644
> > > > --- a/drivers/tty/serial/qcom_geni_serial.c
> > > > +++ b/drivers/tty/serial/qcom_geni_serial.c
> > > > @@ -20,6 +20,7 @@
> > > >  #include <linux/serial.h>
> > > >  #include <linux/serial_core.h>
> > > >  #include <linux/slab.h>
> > > > +#include <linux/suspend.h>
> > > >  #include <linux/tty.h>
> > > >  #include <linux/tty_flip.h>
> > > >  #include <dt-bindings/interconnect/qcom,icc.h>
> > > > @@ -1737,6 +1738,8 @@ static int
> > > > qcom_geni_serial_sys_resume(struct
> > > device *dev)
> > > >       if (uart_console(uport)) {
> > > >               geni_icc_set_tag(&port->se, QCOM_ICC_TAG_ALWAYS);
> > > >               geni_icc_set_bw(&port->se);
> > > > +             if (pm_suspend_via_firmware())
> > >
> > > I'm not familiar with this api, but aren't all our systems
> > > implementing firmware- assisted suspend?
> >
> > Not all the platform supports deep sleep hence to differentiate if
> > resume is from deep sleep suspend or normal suspend, this api is
> > required.
> 
> Can you point me to where this difference in flags is coming from in the
> upstream kernel?

In upstream kernel by default the flag is false, and for deepsleep
support vendor kernel sets this flag true.
> 
> Thanks,
> Bjorn
> 
> > >
> > > Regards,
> > > Bjorn
> > >
> > > > +                     qcom_geni_serial_port_setup(uport);
> > > >       }
> > > >       return ret;
> > > >  }
> > > > --
> > > > 2.17.1
> > > >