Messages in this thread | | | Date | Wed, 26 Jul 2023 13:54:27 +0200 | From | Martin Kaiser <> | Subject | Re: [PATCH v1 1/3] drivers: rng: add check status bit feature |
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Hi Alexey,
Alexey Romanov (AVRomanov@sberdevices.ru) wrote:
> > > +static int meson_rng_wait_status(void __iomem *cfg_addr, int bit) > > > +{ > > > + u32 status; > > > + u32 cnt = 0; > > > + > > > + do { > > > + status = readl_relaxed(cfg_addr) & BIT(bit); > > > + cpu_relax(); > > > + } while (status && (cnt++ < RETRY_CNT)); > > > +
> > Could you use readl_relaxed_poll_timeout here instead of open coding the > > loop?
> At first I also thought about this API. But later I came to the > conclusion that it is inappropriate here:
> 1. We can't call rng_read from an atomic context.
Agreed. A hwrng read function may sleep (an example for this is exynos_trng_do_read). But this doesn't prevent us from using readl_relaxed_poll_timeout.
> 2. RNG for me looks like a very lightweight primitive to me that > should work quiclky.
> But, now I looked again at the API and realized that we can use > readl_relaxed_poll_timeout_atomic() instead of > readl_relaxed_poll_timeout(). What do you think?
Ok, if you know that your rng hardware won't need much time to set the bit that you're checking, you may use readl_relaxed_poll_timeout_atomic.
stm32_rtc_set_alarm does something similar.
Best regards, Martin
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