Messages in this thread | | | Date | Fri, 14 Jan 2022 12:31:35 +0100 | From | Laurent Vivier <> | Subject | Re: [PATCH v6 3/4] clocksource/drivers: Add a goldfish-timer clocksource |
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Le 14/01/2022 à 12:12, Geert Uytterhoeven a écrit : > Hi Laurent, > > On Fri, Jan 14, 2022 at 12:03 PM Laurent Vivier <laurent@vivier.eu> wrote: >> Le 14/01/2022 à 11:46, Arnd Bergmann a écrit : >>> On Thu, Jan 13, 2022 at 9:19 PM Laurent Vivier <laurent@vivier.eu> wrote: >>>> +static int goldfish_timer_set_oneshot(struct clock_event_device *evt) >>>> +{ >>>> + struct goldfish_timer *timerdrv = ced_to_gf(evt); >>>> + void __iomem *base = timerdrv->base; >>>> + >>>> + __raw_writel(0, base + TIMER_ALARM_HIGH); >>>> + __raw_writel(0, base + TIMER_ALARM_LOW); >>>> + __raw_writel(1, base + TIMER_IRQ_ENABLED); >>> >>> As mentioned elsewhere, the __raw_* accessors are not portable, please >>> use readl()/writel() here, or possibly ioread32_be()/iowrite32_be() for >>> the big-endian variant. >> >> We can't use readl()/writel() here because it's supposed to read from a little endian device, and >> goldfish endianness depends on the endianness of the machine. >> >> For goldfish, readl()/writel() works fine on little-endian machine but not on big-endian machine. >> >> On m68k, you have: >> >> #define readl(addr) in_le32(addr) >> #define writel(val,addr) out_le32((addr),(val)) >> >> and with goldfish it's wrong as the device is not little-endian, it is big-endian like the machine. >> >> same comment with ioread32_be()/iowrite32_be(): it will work on big-endian machine not on little-endian. >> >> We need an accessor that doesn't byteswap the value, that accesses it natively, and in all other >> parts of the kernel __raw_writel() and __raw_readl() are used. > > Hence Arnd's suggestion to define custom accessors in the Goldfish > RTC driver, that map to {read,write}l() on little-endian, and to > io{read,write}32_be() on big-endian. > > BTW, I'd go for io{read,write}32() on little endian instead, for > symmetry.
You mean something like that:
#ifdef CONFIG_CPU_BIG_ENDIAN #define raw_ioread32 ioread32be #define raw_iowrite32 iowrite32be #else #define raw_ioread32 ioread32 #define raw_iowrite32 iowrite32 #endif
and then use raw_ioread32()/raw_iowrite32() rather than readl()/writel()?
Thanks, Laurent
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