MIPS: Octeon: Implement delays with cycle counter.

Power throttling make deterministic delay loops impossible.
Re-implement delays using the cycle counter.  This also allows us to
get rid of the code that calculates loops per jiffy.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1317/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 57 insertions, 2 deletions

diff --git a/arch/mips/cavium-octeon/csrc-octeon.c b/arch/mips/cavium-octeon/csrc-octeon.c
index 36400d23ff59..b6847c8e0ddd 100644
--- a/arch/mips/cavium-octeon/csrc-octeon.c
+++ b/arch/mips/cavium-octeon/csrc-octeon.c
@@ -80,3 +80,58 @@ void __init plat_time_init(void)
         clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
         clocksource_register(&clocksource_mips);
 }
+
+static u64 octeon_udelay_factor;
+static u64 octeon_ndelay_factor;
+
+void __init octeon_setup_delays(void)
+{
+        octeon_udelay_factor = octeon_get_clock_rate() / 1000000;
+        /*
+         * For __ndelay we divide by 2^16, so the factor is multiplied
+         * by the same amount.
+         */
+        octeon_ndelay_factor = (octeon_udelay_factor * 0x10000ull) / 1000ull;
+
+        preset_lpj = octeon_get_clock_rate() / HZ;
+}
+
+void __udelay(unsigned long us)
+{
+        u64 cur, end, inc;
+
+        cur = read_c0_cvmcount();
+
+        inc = us * octeon_udelay_factor;
+        end = cur + inc;
+
+        while (end > cur)
+                cur = read_c0_cvmcount();
+}
+EXPORT_SYMBOL(__udelay);
+
+void __ndelay(unsigned long ns)
+{
+        u64 cur, end, inc;
+
+        cur = read_c0_cvmcount();
+
+        inc = ((ns * octeon_ndelay_factor) >> 16);
+        end = cur + inc;
+
+        while (end > cur)
+                cur = read_c0_cvmcount();
+}
+EXPORT_SYMBOL(__ndelay);
+
+void __delay(unsigned long loops)
+{
+        u64 cur, end;
+
+        cur = read_c0_cvmcount();
+        end = cur + loops;
+
+        while (end > cur)
+                cur = read_c0_cvmcount();
+}
+EXPORT_SYMBOL(__delay);
diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
index 8c81a5c5bbab..7216fbd5d79d 100644
--- a/arch/mips/cavium-octeon/setup.c
+++ b/arch/mips/cavium-octeon/setup.c
@@ -594,13 +594,13 @@ void __init prom_init(void)
                  * the filesystem. Also specify the calibration delay
                  * to avoid calculating it every time.
                  */
-                strcat(arcs_cmdline, " rw root=1f00"
-                       " lpj=60176 slram=root,0x40000000,+1073741824");
+                strcat(arcs_cmdline, " rw root=1f00 slram=root,0x40000000,+1073741824");
         }
 
         mips_hpt_frequency = octeon_get_clock_rate();
 
         octeon_init_cvmcount();
+        octeon_setup_delays();
 
         _machine_restart = octeon_restart;
         _machine_halt = octeon_halt;