linux-kernel - [PATCH 3.16 141/366] ASoC: fsl_esai: Fix divisor calculation failure at lower ratio

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Message-ID: <lsq.1539530741.728023490@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Mark Brown" <broonie@...nel.org>,
        "Marek Vasut" <marex@...x.de>,
        "Nicolin Chen" <nicoleotsuka@...il.com>,
        "Fabio Estevam" <fabio.estevam@....com>
Subject: [PATCH 3.16 141/366] ASoC: fsl_esai: Fix divisor calculation
 failure at lower ratio

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nicolin Chen <nicoleotsuka@...il.com>

commit c656941df9bc80f7ec65b92ca73c42f8b0b62628 upstream.

When the desired ratio is less than 256, the savesub (tolerance)
in the calculation would become 0. This will then fail the loop-
search immediately without reporting any errors.

But if the ratio is smaller enough, there is no need to calculate
the tolerance because PM divisor alone is enough to get the ratio.

So a simple fix could be just to set PM directly instead of going
into the loop-search.

Reported-by: Marek Vasut <marex@...x.de>
Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
Tested-by: Marek Vasut <marex@...x.de>
Reviewed-by: Fabio Estevam <fabio.estevam@....com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 sound/soc/fsl/fsl_esai.c | 7 +++++++
 1 file changed, 7 insertions(+)

--- a/sound/soc/fsl/fsl_esai.c
+++ b/sound/soc/fsl/fsl_esai.c
@@ -142,6 +142,13 @@ static int fsl_esai_divisor_cal(struct s
 
 	psr = ratio <= 256 * maxfp ? ESAI_xCCR_xPSR_BYPASS : ESAI_xCCR_xPSR_DIV8;
 
+	/* Do not loop-search if PM (1 ~ 256) alone can serve the ratio */
+	if (ratio <= 256) {
+		pm = ratio;
+		fp = 1;
+		goto out;
+	}
+
 	/* Set the max fluctuation -- 0.1% of the max devisor */
 	savesub = (psr ? 1 : 8)  * 256 * maxfp / 1000;