Messages in this thread | | | Date | Mon, 25 Apr 2022 23:05:12 +0200 | From | Jonathan Neuschäfer <> | Subject | Re: [PATCH v5 04/11] clocksource/drivers: Add HPE GXP timer |
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On Mon, Apr 25, 2022 at 10:38:08PM +0200, Linus Walleij wrote: > On Fri, Apr 22, 2022 at 3:16 PM Arnd Bergmann <arnd@arndb.de> wrote: [...] > The ixp4xx driver looks like that because the register range used for > the timer and the watchdog is combined, i.e. it is a single IP block: > > timer@c8005000 { > compatible = "intel,ixp4xx-timer"; > reg = <0xc8005000 0x100>; > interrupts = <5 IRQ_TYPE_LEVEL_HIGH>; > }; > > Device tree probing does not allow two devices to probe from the same > DT node, so this was solved by letting the (less important) watchdog > be spawn as a platform device from the timer. > > I don't know if double-probing for the same register range can be fixed, > but I was assuming that the one-compatible-to-one-driver assumption > was pretty hard-coded into the abstractions. Maybe it isn't? > > Another way is of course to introduce an MFD. That becomes > problematic in another way: MFD abstractions are supposed to > be inbetween the resource and the devices it spawns, and with > timers/clocksources this creates a horrible special-casing since the > MFD bus (the parent may be providing e.g. an MMIO regmap) > then need to be early-populated and searched by the timer core > from TIMER_OF_DECLARE() early in boot. > > So this solution was the lesser evil that I could think about.
Nuvoton NPCM platforms use yet another approach:
timer0: timer@8000 { compatible = "nuvoton,npcm750-timer"; interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>; reg = <0x8000 0x1C>; clocks = <&clk NPCM7XX_CLK_TIMER>; };
watchdog0: watchdog@801C { compatible = "nuvoton,npcm750-wdt"; interrupts = <GIC_SPI 47 IRQ_TYPE_LEVEL_HIGH>; reg = <0x801C 0x4>; status = "disabled"; clocks = <&clk NPCM7XX_CLK_TIMER>; };
The watchdog control register is in the same register block, but represented by a separate DT node.
(not necessarily a recommendation, but it is another existing approach.)
Jonathan [unhandled content-type:application/pgp-signature] | |