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>

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);

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;

arch/mips/include/asm/mach-cavium-octeon/cpu-feature-overrides.h

@@ -61,22 +61,11 @@
 
 #define kernel_uses_smartmips_rixi (cpu_data[0].cputype == CPU_CAVIUM_OCTEON_PLUS)
 
-#define ARCH_HAS_READ_CURRENT_TIMER 1
 #define ARCH_HAS_IRQ_PER_CPU	1
 #define ARCH_HAS_SPINLOCK_PREFETCH 1
 #define spin_lock_prefetch(x) prefetch(x)
 #define PREFETCH_STRIDE 128
 
-static inline int read_current_timer(unsigned long *result)
-{
-	asm volatile ("rdhwr %0,$31\n"
-#ifndef CONFIG_64BIT
-		      "\tsll %0, 0"
-#endif
-		      : "=r" (*result));
-	return 0;
-}
-
 #ifdef __OCTEON__
 /*
  * All gcc versions that have OCTEON support define __OCTEON__ and have the

arch/mips/include/asm/octeon/octeon.h

@@ -50,6 +50,7 @@ extern void octeon_crypto_disable(struct octeon_cop2_state *state,
 extern asmlinkage void octeon_cop2_restore(struct octeon_cop2_state *task);
 
 extern void octeon_init_cvmcount(void);
+extern void octeon_setup_delays(void);
 
 #define OCTEON_ARGV_MAX_ARGS	64
 #define OCTOEN_SERIAL_LEN	20