Hi Guenter, On Mon, Jan 13, 2025 at 4:08 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > On 1/13/25 04:40, Lad, Prabhakar wrote: > > Hi Biju, > > > > On Mon, Jan 13, 2025 at 11:38 AM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote: > >> > >> Hi Prabhakar, > >> > >>> -----Original Message----- > >>> From: Prabhakar <prabhakar.csengg@xxxxxxxxx> > >>> Sent: 13 January 2025 11:24 > >>> Subject: [PATCH v3 0/6] Add support to retrieve the bootstatus from watchdog for RZ/V2H(P) SoC > >>> > >>> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > >>> > >>> Hi All, > >>> > >>> This patch series adds SYSCON support to retrieve boot status information for RZ/V2H(P) SoC. > >>> Summary of Changes, > >>> > >>> Clock: > >>> Add syscon compatible support to the CPG block in bindings and > >>> device trees. > >>> > >>> Watchdog: > >>> Document the renesas,r9a09g057-syscon-wdt-errorrst property. > >>> Update the watchdog driver to fetch and report boot status via > >>> Error Reset Registers (CPG_ERROR_RSTm). > >>> > >>> Device Tree: > >>> Add the syscon property to CPG and WDT nodes in R9A09G057 and > >>> R9A09G047 SoC DTSI. > >>> > >>> These changes enable the watchdog driver to identify boot sources like Power-on Reset and Watchdog > >>> Reset, improving system diagnostics. > >> > >> This means that, we should assume U-boot/bootloader should not clear the WDT reset status bit. > >> > >> If they clear it, there should be a way to propagate it from u-boot/bootloader to linux, > >> otherwise, we get wrong bootstatus in linux. > >> But the clearing of watchdog status by one of the cases: > >> > >> 1) u-boot identify the boot source and clear the status bit > >> > > I agree, if the tf-a/u-boot clears the register, the bootstatus > > reported by Linux will be in-correct. > > > > I would rephrase that: Today, the boot status is _always_ incorrect if a reboot > was triggered by a watchdog reset. After this patch, it will be correct unless > the boot loader resets the status bit. > Agreed. > > Alternative solution, would be: > > > > Let the TF-A create WDT nodes for us and add a property > > `renesas,r9a09g057-wdt-bootstatus` and propagate the WDT nodes to > > Linux. > > > > renesas,r9a09g057-wdt-bootstatus = <0/1>; > > > > That would require both a property change as well as a change in the bootloader. > I suspect it would also be inappropriate as standard property and would have > to be passed as 'chosen' property (if that is even permitted) or as command line > argument. > > Either case, if the boot loader has to be changed anyway, why not just tell it > to leave the boot status alone ? > It can be done, I think Biju is concerned about the user clearing it, maybe using the `mw` command or the Linux CPG driver clearing it during the probe. Cheers, Prabhakar
