Hi Martin,
thanks for splitting the series into single patches.
Am Donnerstag, 24. August 2023, 21:20:56 CEST schrieb Martin Kaiser:
> Use polling to detect the end of the rngc self test. This is much simpler
> than using an interrupt and a completion.
I'm still not convinced that using polling is simpler. By using
readl_poll_timeout() you will also get an interrupt, the timer one. Why
exactly is using polling much (!) simpler?
> The selftest should take approx. 450us. Keep the overhead to a minimum
> by polling every 500us. (We've already lowered the timeout to 1.5ms.)
I suppose these times only hold true for a specific peripheral clock
frequency. Is it guaranteed that this frequency is fixed?
For using IRQ it's simpler, there is no guessing: you return once the self
test finished. The timeout is identical anyway.
Best regards,
Alexander
> Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
> ---
> v2:
> - use shorter timeout and polling interval
>
> drivers/char/hw_random/imx-rngc.c | 16 +++++++---------
> 1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/char/hw_random/imx-rngc.c
> b/drivers/char/hw_random/imx-rngc.c index 8ff3d46674fd..09523936d2af 100644
> --- a/drivers/char/hw_random/imx-rngc.c
> +++ b/drivers/char/hw_random/imx-rngc.c
> @@ -17,6 +17,7 @@
> #include <linux/hw_random.h>
> #include <linux/completion.h>
> #include <linux/io.h>
> +#include <linux/iopoll.h>
> #include <linux/bitfield.h>
>
> #define RNGC_VER_ID 0x0000
> @@ -101,22 +102,19 @@ static inline void imx_rngc_irq_unmask(struct imx_rngc
> *rngc)
>
> static int imx_rngc_self_test(struct imx_rngc *rngc)
> {
> - u32 cmd;
> + u32 cmd, status;
> int ret;
>
> - imx_rngc_irq_unmask(rngc);
> -
> /* run self test */
> cmd = readl(rngc->base + RNGC_COMMAND);
> writel(cmd | RNGC_CMD_SELF_TEST, rngc->base + RNGC_COMMAND);
>
> - ret = wait_for_completion_timeout(&rngc->rng_op_done,
> -
usecs_to_jiffies(RNGC_SELFTEST_TIMEOUT));
> - imx_rngc_irq_mask_clear(rngc);
> - if (!ret)
> - return -ETIMEDOUT;
> + ret = readl_poll_timeout(rngc->base + RNGC_STATUS, status,
> + status & RNGC_STATUS_ST_DONE, 500,
RNGC_SELFTEST_TIMEOUT);
> + if (ret < 0)
> + return ret;
>
> - return rngc->err_reg ? -EIO : 0;
> + return readl(rngc->base + RNGC_ERROR) ? -EIO : 0;
> }
>
> static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool
> wait)
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