linux-kernel - [PATCH] mmc: mediatek: Fixed bug where clock frequency could be set wrong

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Message-ID: <1488611403-30186-2-git-send-email-yong.mao@mediatek.com>
Date:   Sat, 4 Mar 2017 15:10:03 +0800
From:   Yong Mao <yong.mao@...iatek.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Daniel Kurtz <djkurtz@...omium.org>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        yong mao <yong.mao@...iatek.com>,
        Eddie Huang <eddie.huang@...iatek.com>,
        <linux-mmc@...r.kernel.org>, <srv_heupstream@...iatek.com>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH] mmc: mediatek: Fixed bug where clock frequency could be set wrong

From: yong mao <yong.mao@...iatek.com>

This patch can fix two issues:

Issue 1:
In previous code, div may be overflow when setting clock frequency
as f_min. We can use DIV_ROUND_UP to fix this boundary related
issue.

Issue 2:
In previous code, we can not set the correct clock frequency when
div equals 0xff.

Signed-off-by: Yong Mao <yong.mao@...iatek.com>
Signed-off-by: Chaotian Jing <chaotian.jing@...iatek.com>
---
 drivers/mmc/host/mtk-sd.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index 07f3236..3ad5228 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c
@@ -591,7 +591,7 @@ static void msdc_set_mclk(struct msdc_host *host, unsigned char timing, u32 hz)
 		}
 	}
 	sdr_set_field(host->base + MSDC_CFG, MSDC_CFG_CKMOD | MSDC_CFG_CKDIV,
-			(mode << 8) | (div % 0xff));
+		      (mode << 8) | div);
 	sdr_set_bits(host->base + MSDC_CFG, MSDC_CFG_CKPDN);
 	while (!(readl(host->base + MSDC_CFG) & MSDC_CFG_CKSTB))
 		cpu_relax();
@@ -1692,7 +1692,7 @@ static int msdc_drv_probe(struct platform_device *pdev)
 	host->src_clk_freq = clk_get_rate(host->src_clk);
 	/* Set host parameters to mmc */
 	mmc->ops = &mt_msdc_ops;
-	mmc->f_min = host->src_clk_freq / (4 * 255);
+	mmc->f_min = DIV_ROUND_UP(host->src_clk_freq, 4 * 255);
 
 	mmc->caps |= MMC_CAP_ERASE | MMC_CAP_CMD23;
 	/* MMC core transfer sizes tunable parameters */
-- 
1.7.9.5