Re: [PATCH 0/4] soc: xilinx: pm_domains: cleanup and fix PM_INIT_FINALIZE

[Michael Tretter <m.tretter@pengutronix.de>]

Hi Rajan,

On Thu, 15 Apr 2021 16:27:58 +0000, Rajan Vaja wrote:
> Thanks for the patch.
> 
> > -----Original Message-----
> > From: Michael Tretter <m.tretter@pengutronix.de>
> > Sent: 17 March 2021 09:34 PM
> > To: linux-arm-kernel@lists.infradead.org
> > Cc: Michal Simek <michals@xilinx.com>; Rajan Vaja <RAJANV@xilinx.com>; Jolly
> > Shah <JOLLYS@xilinx.com>; m.tretter@pengutronix.de
> > Subject: [PATCH 0/4] soc: xilinx: pm_domains: cleanup and fix PM_INIT_FINALIZE
> > 
> > Patch 1 of this series fixes the ZynqMP PMU FW power management
> > initialization, which was done by the wrong driver. PM_INIT_FINALIZE must be
> > called from the zynqmp_pm_domains driver, which handles power domains, instead
> > of the zynmp_power driver, which is responsible for suspend and shutdown.
> [Rajan] I am fine with moving to genpd but zynqmp_pm_init_finalize() needs to be late call.
> zynqmp_pm_init_finalize() should be called when Linux has requested all the devices through
> genpd driver. Making it late call will make sure it. 

What is the reason why all devices have to be requested before calling
zynqmp_pm_init_finalize()?

I was expecting that calling PM_INIT_FINALIZE only would tell the PMU_FW that
Linux is using the PM API and the PMU_FW should power down/up PM slaves as
requested by Linux. It is somewhat surprising that this isn't the case and all
PM slaves have to be powered up before calling PM_INIT_FINALIZE.

What would happen if some driver is built as a module? In that case, the
module would be loaded and request the pm node only after PM_INIT_FINALIZE was
called. Do we have to avoid/disallow such cases?

For USB, I am actually observing a similar situation: If I do not request the
USB PM slave before I call PM_INIT_FINALIZE, I see communication errors with
connected USB devices. Could this be related?

Thanks,

Michael

> 
> > 
> > Patches 2 to 4 are various cleanup patches to improve the readability and
> > debugging experience of the zynqmp_pm_domains driver.
> > 
> > Michael
> > 
> > Michael Tretter (4):
> >   soc: xilinx: move PM_INIT_FINALIZE to zynqmp_pm_domains driver
> >   soc: xilinx: cleanup debug and error messages
> >   soc: xilinx: use a properly named field instead of flags
> >   soc: xilinx: add a to_zynqmp_pm_domain macro
> > 
> >  drivers/soc/xilinx/zynqmp_pm_domains.c | 79 +++++++++++++-------------
> >  drivers/soc/xilinx/zynqmp_power.c      |  1 -
> >  2 files changed, 38 insertions(+), 42 deletions(-)
> > 
> > --
> > 2.29.2

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