On Mon, Feb 12, 2018 at 05:44:09PM +0000, Fabrizio Castro wrote: > Dear All, > > 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 Thanks, I have applied the above "dts" and "defconfig" patches for v4.17. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
