spi/pl022: Fix calculate_effective_freq()

calculate_effective_freq() was still not optimized and there were cases when it
returned without error and with values of cpsr and scr as zero.

Also, the variable named found is not used well.

This patch targets to optimize and correct this routine. Tested for SPEAr.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Tested-by: Vinit Kamalaksha Shenoy <vinit.shenoy@st.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-pl022.c

@@ -1681,26 +1681,37 @@ static int calculate_effective_freq(struct pl022 *pl022, int freq, struct
 		while (scr <= SCR_MAX) {
 			tmp = spi_rate(rate, cpsdvsr, scr);
 
-			if (tmp > freq)
+			if (tmp > freq) {
+				/* we need lower freq */
 				scr++;
+				continue;
+			}
+
 			/*
-			 * If found exact value, update and break.
-			 * If found more closer value, update and continue.
+			 * If found exact value, mark found and break.
+			 * If found more closer value, update and break.
 			 */
-			else if ((tmp == freq) || (tmp > best_freq)) {
+			if (tmp > best_freq) {
 				best_freq = tmp;
 				best_cpsdvsr = cpsdvsr;
 				best_scr = scr;
 
 				if (tmp == freq)
-					break;
+					found = 1;
 			}
-			scr++;
+			/*
+			 * increased scr will give lower rates, which are not
+			 * required
+			 */
+			break;
 		}
 		cpsdvsr += 2;
 		scr = SCR_MIN;
 	}
 
+	WARN(!best_freq, "pl022: Matching cpsdvsr and scr not found for %d Hz rate \n",
+			freq);
+
 	clk_freq->cpsdvsr = (u8) (best_cpsdvsr & 0xFF);
 	clk_freq->scr = (u8) (best_scr & 0xFF);
 	dev_dbg(&pl022->adev->dev,