Re: [PATCH 1/3] hwrng: imx-rngc - use polling to detect end of self test

Alexander Stein
2023-08-23T05:23:38Z

Am Dienstag, 22. August 2023, 17:25:51 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.
>
> Active waiting is no disadvantage here. The self test is run during
> probe, there's nothing we could do in parallel at this time.

If this driver is built-in you are stalling the boot process while polling,
no? Unless probe_type = PROBE_PREFER_ASYNCHRONOUS is set of course.

Best regards,
Alexander

> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> ---
> drivers/char/hw_random/imx-rngc.c | 15 +++++++--------
> 1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/char/hw_random/imx-rngc.c
> b/drivers/char/hw_random/imx-rngc.c index e4b385b01b11..85207535fd12 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
> @@ -101,21 +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,
> msecs_to_jiffies(RNGC_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, 1000,
RNGC_TIMEOUT * 1000);
> + 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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