[PATCH v5 00/26] Fix watchdog on Renesas R-Car Gen2 and RZ/G1

Thu Feb 22 00:38:39 PST 2018

Hi Simon,

On Wed, Feb 21, 2018 at 7:32 PM, Simon Horman <horms at verge.net.au> wrote:
> On Wed, Feb 21, 2018 at 05:30:12PM +0100, Geert Uytterhoeven wrote:
>> On Wed, Feb 21, 2018 at 5:13 PM, Simon Horman <horms at verge.net.au> wrote:
>> > On Tue, Feb 20, 2018 at 01:51:28PM +0100, Geert Uytterhoeven wrote:
>> >> On Mon, Feb 12, 2018 at 6:44 PM, Fabrizio Castro
>> >> <fabrizio.castro at bp.renesas.com> wrote:
>> >> > this series has been around for some time as RFC, and it has collected
>> >> > useful comments from the community along the way.
>> >> > The solution proposed by this patch set works for most R-Car Gen2 and
>> >> > RZ/G1 devices, but not all of them. We now know that for some R-Car
>> >> > Gen2 early revisions there is no proper software fix. Anyway, no
>> >> > product has been built around early revisions, but development boards
>> >> > mounting early revisions (basically prototypes) are still out there.
>> >> > As a result, this series isn't enabling the internal watchdog on R-Car
>> >> > Gen2 boards, developers may enable it in board specific device trees
>> >> > if needed.
>> >> > This series has been tested by me on the iwg20d, iwg22d, Lager, Alt,
>> >> > and Koelsch boards.
>> >> >
>> >> > The problem
>> >> > ===========
>> >> > To deal with SMP on R-Car Gen2 and RZ/G1, we install a reset vector
>> >> > to ICRAM1 and we program the [S]BAR registers so that when we turn ON
>> >> > the non-boot CPUs they are redirected to the reset vector installed by
>> >> > Linux in ICRAM1, and eventually they continue the execution to RAM,
>> >> > where the SMP bring-up code will take care of the rest.
>> >> > The content of the [S]BAR registers survives a watchdog triggered reset,
>> >> > and as such after the watchdog fires the boot core will try and execute
>> >> > the SMP bring-up code instead of jumping to the bootrom code.
>> >> >
>> >> > The fix
>> >> > =======
>> >> > The main strategy for the solution is to let the reset vector decide
>> >> > if it needs to jump to shmobile_boot_fn or to the bootrom code.
>> >> > In a watchdog triggered reset scenario, since the [S]BAR registers keep
>> >> > their values, the boot CPU will jump into the newly designed reset
>> >> > vector, the assembly routine will eventually test WOVF (a bit in register
>> >> > RWTCSRA that indicates if the watchdog counter has overflown, the value
>> >> > of this bit gets retained in this scenario), and jump to the bootrom code
>> >> > which will in turn load up the bootloader, etc.
>> >> > When bringing up SMP or using CPU hotplug, the reset vector will jump
>> >> > to shmobile_boot_fn instead.
>> >> >
>> >> > Thank you All for your help.
>> >> >
>> >> > Best regards,
>> >> >
>> >> > Fabrizio Castro (26):
>> >> >   ARM: shmobile: Add watchdog support
>> >> >   ARM: dts: r8a7743: Adjust SMP routine size
>> >> >   ARM: dts: r8a7745: Adjust SMP routine size
>> >> >   ARM: dts: r8a7790: Adjust SMP routine size
>> >> >   ARM: dts: r8a7791: Adjust SMP routine size
>> >> >   ARM: dts: r8a7792: Adjust SMP routine size
>> >> >   ARM: dts: r8a7793: Adjust SMP routine size
>> >> >   ARM: dts: r8a7794: Adjust SMP routine size
>> >> >   soc: renesas: rcar-rst: Enable watchdog as reset trigger for Gen2
>> >> >   ARM: shmobile: rcar-gen2: Add watchdog support
>> >> >   dt-bindings: watchdog: renesas-wdt: Add R-Car Gen2 support
>> >> >   watchdog: renesas_wdt: Add R-Car Gen2 support
>> >> >   watchdog: renesas_wdt: Add restart handler
>> >> >   ARM: shmobile: defconfig: Enable RENESAS_WDT_GEN
>> >> >   clk: renesas: r8a7743: Add rwdt clock
>> >> >   clk: renesas: r8a7745: Add rwdt clock
>> >> >   clk: renesas: r8a7790: Add rwdt clock
>> >> >   clk: renesas: r8a7791/r8a7793: Add rwdt clock
>> >> >   clk: renesas: r8a7794: Add rwdt clock
>> >> >   ARM: dts: r8a7743: Add watchdog support to SoC dtsi
>> >> >   ARM: dts: r8a7745: Add watchdog support to SoC dtsi
>> >> >   ARM: dts: r8a7790: Add watchdog support to SoC dtsi
>> >> >   ARM: dts: r8a7791: Add watchdog support to SoC dtsi
>> >> >   ARM: dts: r8a7794: Add watchdog support to SoC dtsi
>> >> >   ARM: dts: iwg20m: Add watchdog support to SoM dtsi
>> >> >   ARM: dts: iwg22m: Add watchdog support to SoM dtsi
>> >> >
>> >> >  .../devicetree/bindings/watchdog/renesas-wdt.txt   | 19 ++++++--
>> >> >  arch/arm/boot/dts/r8a7743-iwg20m.dtsi              |  5 ++
>> >> >  arch/arm/boot/dts/r8a7743.dtsi                     | 12 ++++-
>> >> >  arch/arm/boot/dts/r8a7745-iwg22m.dtsi              |  5 ++
>> >> >  arch/arm/boot/dts/r8a7745.dtsi                     | 12 ++++-
>> >> >  arch/arm/boot/dts/r8a7790.dtsi                     | 12 ++++-
>> >> >  arch/arm/boot/dts/r8a7791.dtsi                     | 12 ++++-
>> >> >  arch/arm/boot/dts/r8a7792.dtsi                     |  2 +-
>> >> >  arch/arm/boot/dts/r8a7793.dtsi                     |  2 +-
>> >> >  arch/arm/boot/dts/r8a7794.dtsi                     | 12 ++++-
>> >> >  arch/arm/configs/shmobile_defconfig                |  1 +
>> >> >  arch/arm/mach-shmobile/common.h                    |  6 +++
>> >> >  arch/arm/mach-shmobile/headsmp.S                   | 55 ++++++++++++++++++++++
>> >> >  arch/arm/mach-shmobile/platsmp-apmu.c              |  1 +
>> >> >  arch/arm/mach-shmobile/pm-rcar-gen2.c              | 15 ++++--
>> >> >  drivers/clk/renesas/r8a7743-cpg-mssr.c             |  2 +
>> >> >  drivers/clk/renesas/r8a7745-cpg-mssr.c             |  2 +
>> >> >  drivers/clk/renesas/r8a7790-cpg-mssr.c             |  2 +
>> >> >  drivers/clk/renesas/r8a7791-cpg-mssr.c             |  2 +
>> >> >  drivers/clk/renesas/r8a7794-cpg-mssr.c             |  2 +
>> >> >  drivers/soc/renesas/rcar-rst.c                     | 35 +++++++++++---
>> >> >  drivers/watchdog/renesas_wdt.c                     | 39 +++++++++++++--
>> >>
>> >> Thanks, I've queued the clock patches in clk-renesas-for-v4.17, as they are
>> >> a hard dependency for:
>> >>   (1) The new reset vector in arch/arm/mach-shmobile/
>> >>   (2) The watchdog driver.
>> >>
>> >> Note that the watchdog driver itself (2) has a hard dependency on the
>> >> new reset vector (1).
>> >
>> > Thanks, I have marked the watchdog driver patch as Deferred.
>> > Please resubmit or otherwise ping me once they dependencies
>> > are in an rc release.
>>
>> I gave the dependencies a bit more thought.
>>
>> I think we can gain once release cycle if you would postpone the DTS patches
>> (both SMP routine size adjustments and RWDT device node additions) to v4.18.
>> Then all other parts can be upstreamed in parallel in v4.17, as nothing
>> will be activated before the DTS parts are in.
>>
>> Does this look sane?
>
> What about new DTS on old kernels of a specific vintage?

New DTS would work fine on v4.16 and older, which don't have any of the
other patches from this series.
New DTS would work fine on v4.17, assumed all other patches from this
series get into v4.17.

The only issue would be a new DTS on a kernel that has some but not all
other patches from this series.

If we want to fast-track everything into v4.17, we need a stable branch, to be
pulled by all 5 actors (clk-renesas, mach-shmobile, soc-renesas, watchdog,
renesas-dts).

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds