linux-kernel - [PATCH v3 8/9] spi: spi-s3c64xx: Increase transfer timeout

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Message-Id: <20201002122243.26849-9-l.stelmach@samsung.com>
Date:   Fri,  2 Oct 2020 14:22:42 +0200
From:   Łukasz Stelmach <l.stelmach@...sung.com>
To:     Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Andi Shyti <andi@...zian.org>, Mark Brown <broonie@...nel.org>,
        linux-spi@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>,
        Łukasz Stelmach <l.stelmach@...sung.com>
Subject: [PATCH v3 8/9] spi: spi-s3c64xx: Increase transfer timeout

Increase timeout by 30 ms for some wiggle room and set the minimum value
to 100 ms. This ensures a non-zero value for short transfers which
may take less than 1 ms. The timeout value does not affect
performance because it is used with a completion.

Similar formula is used in other drivers e.g. sun4i, sun6i.

Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>
Signed-off-by: Łukasz Stelmach <l.stelmach@...sung.com>
---
 drivers/spi/spi-s3c64xx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index 0bd3e230350c..9f728a7c59a1 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -473,7 +473,8 @@ static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
 
 	/* millisecs to xfer 'len' bytes @ 'cur_speed' */
 	ms = xfer->len * 8 * 1000 / sdd->cur_speed;
-	ms += 10; /* some tolerance */
+	ms += 30;               /* some tolerance */
+	ms = max(ms, 100);      /* minimum timeout */
 
 	val = msecs_to_jiffies(ms) + 10;
 	val = wait_for_completion_timeout(&sdd->xfer_completion, val);
-- 
2.26.2