linux-kernel - [PATCH v2 3/6] hwrng: imx-rngc - use polling to detect end of self test

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Message-Id: <20230824192059.1569591-4-martin@kaiser.cx>
Date:   Thu, 24 Aug 2023 21:20:56 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Alexander Stein <alexander.stein@...tq-group.com>,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Martin Kaiser <martin@...ser.cx>
Subject: [PATCH v2 3/6] hwrng: imx-rngc - use polling to detect end of self test

Use polling to detect the end of the rngc self test. This is much simpler
than using an interrupt and a completion.

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.)

Signed-off-by: Martin Kaiser <martin@...ser.cx>
---
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)
-- 
2.39.2