Re: [PATCH 1/1] bus: mhi: host: allow SBL as initial EE

[Manivannan Sadhasivam <mani@kernel.org>]

On Tue, May 30, 2023 at 01:12:59PM +0200, Daniele Palmas wrote:
> Hi Mani,
> 
> Il giorno mar 30 mag 2023 alle ore 12:31 Manivannan Sadhasivam
> <mani@kernel.org> ha scritto:
> >
> > On Tue, May 30, 2023 at 11:13:40AM +0200, Daniele Palmas wrote:
> > > There are situations in which SBL is a legitimate initial execution
> > > environment (e.g. modem stuck in SBL due to a firmware failure...), but
> > > mhi refuses to start:
> > >
> > > mhi-pci-generic 0000:01:00.0: MHI PCI device found: foxconn-sdx55
> > > mhi-pci-generic 0000:01:00.0: BAR 0: assigned
> > > mhi-pci-generic 0000:01:00.0: enabling device (0000 -> 0002)
> > > mhi mhi0: Requested to power ON
> > > mhi mhi0: SECONDARY BOOTLOADER is not a valid EE for power on
> > > mhi-pci-generic 0000:01:00.0: failed to power up MHI controller
> > > mhi-pci-generic: probe of 0000:01:00.0 failed with error -5
> > >
> > > Fix this by adding SBL as an allowed initial execution environment.
> > >
> >
> > What can you do with the modem when firmware failure happens? If there is a
> > usecase, please explain.
> 
> (removing Siddartha and Sujeev due to addresses not working)
> 

Both left Qualcomm a while ago...

> A possible scenario for a Telit modem not being able to go to mission
> mode is when a firmware update does not work properly: in this case it
> remains stuck in SBL, but the SAHARA device can be used for retrying
> the firmware update.
> 

So IIUC, while updating SBL over SAHARA channel, the firmware update could be
corrupted and the device would get stuck in SBL EE. In that case, the SAHARA
channel exposed by PBL will still be open and that could be used to retry the
firmware update. Am I right?

Looks like PBL is doing a fail safe upgrade!

> Telit FN990 supports the SAHARA channels in pci_generic. It's true
> that there's still missing the exposed device for userspace, something
> that we are currently managing with out of tree patches, but I see
> that there's some ongoing effort for that
> https://lore.kernel.org/mhi/20230522190459.13790-1-quic_jhugo@quicinc.com/
> 
> I'm not sure if non-Telit modems have other reasonable use-cases.
> 

If my above understanding is correct, then this patch will benefit other
platforms too.

- Mani

> Regards,
> Daniele
> 
> >
> > - Mani
> >
> > > Fixes: 3000f85b8f47 ("bus: mhi: core: Add support for basic PM operations")
> > > Signed-off-by: Daniele Palmas <dnlplm@gmail.com>
> > > ---
> > >  drivers/bus/mhi/host/internal.h | 2 +-
> > >  drivers/bus/mhi/host/pm.c       | 3 ++-
> > >  2 files changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/bus/mhi/host/internal.h b/drivers/bus/mhi/host/internal.h
> > > index 2e139e76de4c..3bdcd2321aa5 100644
> > > --- a/drivers/bus/mhi/host/internal.h
> > > +++ b/drivers/bus/mhi/host/internal.h
> > > @@ -56,7 +56,7 @@ extern const char * const mhi_ee_str[MHI_EE_MAX];
> > >
> > >  #define MHI_IN_PBL(ee) (ee == MHI_EE_PBL || ee == MHI_EE_PTHRU || \
> > >                       ee == MHI_EE_EDL)
> > > -#define MHI_POWER_UP_CAPABLE(ee) (MHI_IN_PBL(ee) || ee == MHI_EE_AMSS)
> > > +#define MHI_POWER_UP_CAPABLE(ee) (MHI_IN_PBL(ee) || ee == MHI_EE_AMSS || ee == MHI_EE_SBL)
> > >  #define MHI_FW_LOAD_CAPABLE(ee) (ee == MHI_EE_PBL || ee == MHI_EE_EDL)
> > >  #define MHI_IN_MISSION_MODE(ee) (ee == MHI_EE_AMSS || ee == MHI_EE_WFW || \
> > >                                ee == MHI_EE_FP)
> > > diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> > > index 083459028a4b..18872c5017be 100644
> > > --- a/drivers/bus/mhi/host/pm.c
> > > +++ b/drivers/bus/mhi/host/pm.c
> > > @@ -1203,10 +1203,11 @@ int mhi_sync_power_up(struct mhi_controller *mhi_cntrl)
> > >
> > >       wait_event_timeout(mhi_cntrl->state_event,
> > >                          MHI_IN_MISSION_MODE(mhi_cntrl->ee) ||
> > > +                        mhi_cntrl->ee == MHI_EE_SBL ||
> > >                          MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state),
> > >                          msecs_to_jiffies(mhi_cntrl->timeout_ms));
> > >
> > > -     ret = (MHI_IN_MISSION_MODE(mhi_cntrl->ee)) ? 0 : -ETIMEDOUT;
> > > +     ret = (MHI_IN_MISSION_MODE(mhi_cntrl->ee) || mhi_cntrl->ee == MHI_EE_SBL) ? 0 : -ETIMEDOUT;
> > >       if (ret)
> > >               mhi_power_down(mhi_cntrl, false);
> > >
> > > --
> > > 2.37.1
> > >
> >
> > --
> > மணிவண்ணன் சதாசிவம்

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