palm_bk3710: fix IDECLK period calculation
Sergei Shtylyov [Tue, 8 Jul 2008 17:27:22 +0000 (19:27 +0200)]
The driver uses completely bogus rounding formula for calculating period from
the IDECLK frequency which gives one-off period values (e.g. 11 ns with 100 MHz
IDECLK) which in turn can lead to overclocked IDE transfer timings.  Actually,
rounding is just wrong in this case, so use a mere division for a safe result.

While at it, also:

- give 'ide_palm_clk' variable a more suitable name;

- get rid of the useless 'ideclkp' variable;

- drop the LISP stype 'p' postfix from the 'clkp' variable's name. :-)

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: mcherkashin@ru.mvista.com
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/arm/palm_bk3710.c

index cc24803..2f2b4f4 100644 (file)
@@ -76,7 +76,7 @@ struct palm_bk3710_udmatiming {
 
 #include "../ide-timing.h"
 
-static long ide_palm_clk;
+static unsigned ideclk_period; /* in nanoseconds */
 
 static const struct palm_bk3710_udmatiming palm_bk3710_udmatimings[6] = {
        {160, 240},             /* UDMA Mode 0 */
@@ -86,8 +86,6 @@ static const struct palm_bk3710_udmatiming palm_bk3710_udmatimings[6] = {
        {85,  60},              /* UDMA Mode 4 */
 };
 
-static struct clk *ideclkp;
-
 static void palm_bk3710_setudmamode(void __iomem *base, unsigned int dev,
                                    unsigned int mode)
 {
@@ -97,10 +95,10 @@ static void palm_bk3710_setudmamode(void __iomem *base, unsigned int dev,
 
        /* DMA Data Setup */
        t0 = DIV_ROUND_UP(palm_bk3710_udmatimings[mode].cycletime,
-                         ide_palm_clk) - 1;
-       tenv = DIV_ROUND_UP(20, ide_palm_clk) - 1;
+                         ideclk_period) - 1;
+       tenv = DIV_ROUND_UP(20, ideclk_period) - 1;
        trp = DIV_ROUND_UP(palm_bk3710_udmatimings[mode].rptime,
-                          ide_palm_clk) - 1;
+                          ideclk_period) - 1;
 
        /* udmatim Register */
        val16 = readw(base + BK3710_UDMATIM) & (dev ? 0xFF0F : 0xFFF0);
@@ -141,8 +139,8 @@ static void palm_bk3710_setdmamode(void __iomem *base, unsigned int dev,
        cycletime = max_t(int, t->cycle, min_cycle);
 
        /* DMA Data Setup */
-       t0 = DIV_ROUND_UP(cycletime, ide_palm_clk);
-       td = DIV_ROUND_UP(t->active, ide_palm_clk);
+       t0 = DIV_ROUND_UP(cycletime, ideclk_period);
+       td = DIV_ROUND_UP(t->active, ideclk_period);
        tkw = t0 - td - 1;
        td -= 1;
 
@@ -168,9 +166,9 @@ static void palm_bk3710_setpiomode(void __iomem *base, ide_drive_t *mate,
        struct ide_timing *t;
 
        /* PIO Data Setup */
-       t0 = DIV_ROUND_UP(cycletime, ide_palm_clk);
+       t0 = DIV_ROUND_UP(cycletime, ideclk_period);
        t2 = DIV_ROUND_UP(ide_timing_find_mode(XFER_PIO_0 + mode)->active,
-                         ide_palm_clk);
+                         ideclk_period);
 
        t2i = t0 - t2 - 1;
        t2 -= 1;
@@ -192,8 +190,8 @@ static void palm_bk3710_setpiomode(void __iomem *base, ide_drive_t *mate,
 
        /* TASKFILE Setup */
        t = ide_timing_find_mode(XFER_PIO_0 + mode);
-       t0 = DIV_ROUND_UP(t->cyc8b, ide_palm_clk);
-       t2 = DIV_ROUND_UP(t->act8b, ide_palm_clk);
+       t0 = DIV_ROUND_UP(t->cyc8b, ideclk_period);
+       t2 = DIV_ROUND_UP(t->act8b, ideclk_period);
 
        t2i = t0 - t2 - 1;
        t2 -= 1;
@@ -350,22 +348,22 @@ static const struct ide_port_info __devinitdata palm_bk3710_port_info = {
 
 static int __devinit palm_bk3710_probe(struct platform_device *pdev)
 {
-       struct clk *clkp;
+       struct clk *clk;
        struct resource *mem, *irq;
        ide_hwif_t *hwif;
-       unsigned long base;
+       unsigned long base, rate;
        int i;
        hw_regs_t hw;
        u8 idx[4] = { 0xff, 0xff, 0xff, 0xff };
 
-       clkp = clk_get(NULL, "IDECLK");
-       if (IS_ERR(clkp))
+       clk = clk_get(NULL, "IDECLK");
+       if (IS_ERR(clk))
                return -ENODEV;
 
-       ideclkp = clkp;
-       clk_enable(ideclkp);
-       ide_palm_clk = clk_get_rate(ideclkp)/100000;
-       ide_palm_clk = (10000/ide_palm_clk) + 1;
+       clk_enable(clk);
+       rate = clk_get_rate(clk);
+       ideclk_period = 1000000000UL / rate;
+
        /* Register the IDE interface with Linux ATA Interface */
        memset(&hw, 0, sizeof(hw));