[PATCH 1/5] clk: mvebu: Add core-divider clock

On Thu, Sep 26, 2013 at 10:24:04AM +0200, Andrew Lunn wrote:

Hi Ezequiel

quoted

+static int clk_corediv_enable(struct clk_hw *hwclk)
+{
+	struct clk_corediv *corediv = to_corediv_clk(hwclk);
+	struct clk_corediv_desc *desc = &corediv->desc;
+	u32 reg;
+
+	reg = readl(corediv->reg);
+	reg |= (BIT(desc->fieldbit) << CORE_CLOCK_DIVIDER_ENABLE_OFFSET);
+	writel(reg, corediv->reg);
+	return 0;
+}

Shouldn't there be spinlocks around these register accesses? At least
the core gate clk driver has a spinlock.

Indeed.

quoted

+static long clk_corediv_round_rate(struct clk_hw *hwclk, unsigned long rate,
+	     				          unsigned long *parent_rate)
+{
+	/* Valid ratio are 1:4, 1:5, 1:6 and 1:8 */
+	u32 div;
+
+	div = *parent_rate / rate;
+	if (div <= 4)
+	   div = 4;
+	   else if (div <= 5)
+	   	div = 5;
+		else if (div <= 6)
+		     div = 6;
+		     else
+			div = 8;
+
+	return *parent_rate / div;
+}

This looks odd. Is not the following clearer?

	div = *parent_rate / rate;
	if (div < 5)
	   div = 4;
	   else if (div > 6)
		div = 8;

The CodingStyle might require some {} here?

Mmmm... no, it's not at all clearer to me.
IMHO, the original construction explicitly show the possible ratios:

	/* If it's smaller than or equal to 4, set to 4 */
	if (div <= 4)
		div = 4;

	/* Otherwise, if it's between 4 and 5, set to 5 */
	else if (div <= 5)
	 	div = 5;

	/* Otherwise, if it's between 5 and 6, set to 6 */
	else if (div <= 6)
		div = 6;

	/* Otherwise, if it's bigger than 6, set to 8 */
	else
		div = 8;

(And I don't think we need any braces).

Is this not clear?

+   /*
+    * Wait for clocks to settle down, and then clear all the
+     * ratios request and the reload request.
+      */
+      udelay(1000);
+      reg &= ~(CORE_CLOCK_DIVIDER_RATIO_MASK | CORE_CLOCK_DIVIDER_RATIO_RELOAD);
+      writel(reg, corediv->reg);
+      udelay(1000);


Documentation/timers/timers-howto.txt says: 

       SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
       		* Use usleep_range

Right, forgot about that as well...

Thanks for the feedback!
-- 
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com