linux-kernel - [PATCH v2 4/7] LPC32xx: clock.c: MMC update

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Date:	Mon, 30 Jan 2012 17:02:03 +0100
From:	Roland Stigge <stigge@...com.de>
To:	w.sang@...gutronix.de, bangaragiri.g@....com,
	srinivas.bakki@....com, sundarapandian.andithevar@....com,
	linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
	kevin.wells@....com, grant.likely@...retlab.ca,
	linux-arm-kernel@...ts.infradead.org
Cc:	Roland Stigge <stigge@...com.de>
Subject: [PATCH v2 4/7] LPC32xx: clock.c: MMC update

This patch updates MMC clocking in clock.c:
* No manual MMC clock enable/disable on MMC register access necessary
  (it's the MMC IP clock, not the MMC CLK signal rate)  
* Added comments

Signed-off-by: Roland Stigge <stigge@...com.de>

diff --git a/arch/arm/mach-lpc32xx/clock.c b/arch/arm/mach-lpc32xx/clock.c
index 17709ca..229bec5 100644
--- a/arch/arm/mach-lpc32xx/clock.c
+++ b/arch/arm/mach-lpc32xx/clock.c
@@ -738,14 +738,9 @@ static int mmc_onoff_enable(struct clk *clk, int enable)
 
 static unsigned long mmc_get_rate(struct clk *clk)
 {
-	u32 div, rate, oldclk;
+	u32 div, rate;
 
-	/* The MMC clock must be on when accessing an MMC register */
-	oldclk = __raw_readl(LPC32XX_CLKPWR_MS_CTRL);
-	__raw_writel(oldclk | LPC32XX_CLKPWR_MSCARD_SDCARD_EN,
-		LPC32XX_CLKPWR_MS_CTRL);
 	div = __raw_readl(LPC32XX_CLKPWR_MS_CTRL);
-	__raw_writel(oldclk, LPC32XX_CLKPWR_MS_CTRL);
 
 	/* Get the parent clock rate */
 	rate = clk->parent->get_rate(clk->parent);
@@ -773,32 +768,36 @@ static unsigned long mmc_round_rate(struct clk *clk, unsigned long rate)
 	if (div > 0xf)
 		div = 0xf;
 
+	/*
+	 * The divider is forced to 1 to keep the SD clock granularity
+	 * good. Using a non-0 divider will limit the SD card clock rates
+	 * the SD driver can generate. Remove it if your feeling crazy.
+	 */
+	div = 1;
+
 	return prate / div;
 }
 
 static int mmc_set_rate(struct clk *clk, unsigned long rate)
 {
-	u32 oldclk, tmp;
+	u32 tmp;
 	unsigned long prate, div, crate = mmc_round_rate(clk, rate);
 
 	prate = clk->parent->get_rate(clk->parent);
 
 	div = prate / crate;
 
-	/* The MMC clock must be on when accessing an MMC register */
-	oldclk = __raw_readl(LPC32XX_CLKPWR_MS_CTRL);
-	__raw_writel(oldclk | LPC32XX_CLKPWR_MSCARD_SDCARD_EN,
-		LPC32XX_CLKPWR_MS_CTRL);
 	tmp = __raw_readl(LPC32XX_CLKPWR_MS_CTRL) &
 		~LPC32XX_CLKPWR_MSCARD_SDCARD_DIV(0xf);
 	tmp |= LPC32XX_CLKPWR_MSCARD_SDCARD_DIV(div);
 	__raw_writel(tmp, LPC32XX_CLKPWR_MS_CTRL);
 
-	__raw_writel(oldclk, LPC32XX_CLKPWR_MS_CTRL);
-
 	return 0;
 }
 
+/*
+ * This is the MMC IP clock, not the MMC CLK signal rate!
+ */
 static struct clk clk_mmc = {
 	.parent		= &clk_armpll,
 	.set_rate	= mmc_set_rate,
--
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