mips: mt76x8: ddr_cal: Correct dqs_find_min/max implementations

The current implementations have some issues detecting the correct
values:

dqs_find_max() will return "last passing fieldval + 1" instead of
"last passing fieldval". Also it will return "maxval + 1" in the
case that all fieldvals are tested valid (without error).

dqs_find_min() will not test the "lowest" value because of using ">"
instead of ">=".

This patch now rewrites these functions to fix those issues. Also,
this patch uses the same approach of a for loop in both functions making
it easier to read and maintain.

Since the variables are integers now, we can use min()/max(), which
handles the wrap around case for fieldval=0: return (0 - 1).

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Weijie Gao <weijie.gao@mediatek.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Reviewed-by: Weijie Gao <weijie.gao@mediatek.com>

diff --git a/arch/mips/mach-mtmips/ddr_cal.c b/arch/mips/mach-mtmips/ddr_cal.c
index 80a058d..71a53c3 100644 (file)
--- a/arch/mips/mach-mtmips/ddr_cal.c
+++ b/arch/mips/mach-mtmips/ddr_cal.c
@@ -74,39 +74,31 @@ static inline bool dqs_test_error(void __iomem *memc, u32 memsize, u32 dqsval,
 static inline int dqs_find_max(void __iomem *memc, u32 memsize, int initval,
                               int maxval, int shift, u32 regval)
 {
-       int fieldval = initval;
+       int fieldval;
        u32 dqsval;
 
-       do {
+       for (fieldval = initval; fieldval <= maxval; fieldval++) {
                dqsval = regval | (fieldval << shift);
-
                if (dqs_test_error(memc, memsize, dqsval, 3))
-                       break;
-
-               fieldval++;
-       } while (fieldval <= maxval);
+                       return max(fieldval - 1, initval);
+       }
 
-       return fieldval;
+       return maxval;
 }
 
 static inline int dqs_find_min(void __iomem *memc, u32 memsize, int initval,
                               int minval, int shift, u32 regval)
 {
-       int fieldval = initval;
+       int fieldval;
        u32 dqsval;
 
-       while (fieldval > minval) {
+       for (fieldval = initval; fieldval >= minval; fieldval--) {
                dqsval = regval | (fieldval << shift);
-
-               if (dqs_test_error(memc, memsize, dqsval, 1)) {
-                       fieldval++;
-                       break;
-               }
-
-               fieldval--;
+               if (dqs_test_error(memc, memsize, dqsval, 1))
+                       return min(fieldval + 1, initval);
        }
 
-       return fieldval;
+       return minval;
 }
 
 void ddr_calibrate(void __iomem *memc, u32 memsize, u32 bw)