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

[Geert Uytterhoeven]

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).

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