sdhci-of: cleanup eSDHC's set_clock() a little bit

- Get rid of incomprehensible "if { for { if } }" construction for the
  exponential divisor calculation. The first if statement isn't correct
  at all, since it should check for "host->max_clk / pre_div / 16 >
  clock". The error doesn't cause any bugs because the check in the for
  loop does the right thing, and so the outer check becomes useless;

- For the linear divisor do the same: a single while statement is more
  readable than for + if construction;

- Add dev_dbg() that prints desired and actual clock frequency.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: David Vrabel <david.vrabel@csr.com>
Cc: Ben Dooks <ben@fluff.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 11 deletions

diff --git a/drivers/mmc/host/sdhci-of.c b/drivers/mmc/host/sdhci-of.c
index c8dab07e34b8..01ab916c2802 100644
--- a/drivers/mmc/host/sdhci-of.c
+++ b/drivers/mmc/host/sdhci-of.c
@@ -121,8 +121,8 @@ static void esdhc_writeb(struct sdhci_host *host, u8 val, int reg)
 
 static void esdhc_set_clock(struct sdhci_host *host, unsigned int clock)
 {
-        int div;
         int pre_div = 2;
+        int div = 1;
 
         clrbits32(host->ioaddr + ESDHC_SYSTEM_CONTROL, ESDHC_CLOCK_IPGEN |
                   ESDHC_CLOCK_HCKEN | ESDHC_CLOCK_PEREN | ESDHC_CLOCK_MASK);
@@ -130,17 +130,14 @@ static void esdhc_set_clock(struct sdhci_host *host, unsigned int clock)
         if (clock == 0)
                 goto out;
 
-        if (host->max_clk / 16 > clock) {
-                for (; pre_div < 256; pre_div *= 2) {
-                        if (host->max_clk / pre_div < clock * 16)
-                                break;
-                }
-        }
+        while (host->max_clk / pre_div / 16 > clock && pre_div < 256)
+                pre_div *= 2;
 
-        for (div = 1; div <= 16; div++) {
-                if (host->max_clk / (div * pre_div) <= clock)
-                        break;
-        }
+        while (host->max_clk / pre_div / div > clock && div < 16)
+                div++;
+
+        dev_dbg(mmc_dev(host->mmc), "desired SD clock: %d, actual: %d\n",
+                clock, host->max_clk / pre_div / div);
 
         pre_div >>= 1;
         div--;