lib: Unify log2() and related functions

This patch adds a few bit counting functions that are commonly needed
for certain register calculations. We previously had a log2()
implementation already, but it was awkwardly split between some C code
that's only available in ramstage and an optimized x86-specific
implementation in pre-RAM that prevented other archs from pulling it
into earlier stages.

Using __builtin_clz() as the baseline allows GCC to inline optimized
assembly for most archs (including CLZ on ARM/ARM64 and BSR on x86), and
to perform constant-folding if possible. What was previously named log2f
on pre-RAM x86 is now ffs, since that's the standard name for that
operation and I honestly don't have the slightest idea how it could've
ever ended up being called log2f (which in POSIX is 'binary(2) LOGarithm
with Float result, whereas the Find First Set operation has no direct
correlation to logarithms that I know of). Make ffs result 0-based
instead of the POSIX standard's 1-based since that is consistent with
clz, log2 and the former log2f, and generally closer to what you want
for most applications (a value that can directly be used as a shift to
reach the found bit). Call it __ffs() instead of ffs() to avoid problems
when importing code, since that's what Linux uses for the 0-based
operation.

CQ-DEPEND=CL:273023
BRANCH=None
BUG=None
TEST=Built on Big, Falco, Jerry, Oak and Urara. Compared old and new
log2() and __ffs() results on Falco for a bunch of test values.

Change-Id: I599209b342059e17b3130621edb6b6bbeae26876
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 3701a16ae944ecff9c54fa9a50d28015690fcb2f
Original-Change-Id: I60f7cf893792508188fa04d088401a8bca4b4af6
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/273008
Original-Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10394
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

16 files changed, 86 insertions, 126 deletions

diff --git a/src/arch/arm/include/utils.h b/src/arch/arm/include/utils.h
deleted file mode 100644
index 2482c6bf57..0000000000
--- a/src/arch/arm/include/utils.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * (C) Copyright 2010
- * Texas Instruments, <www.ti.com>
- * Aneesh V <aneesh@ti.com>
- *
- * See file CREDITS for list of people who contributed to this
- * project.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc.
- */
-#ifndef _UTILS_H_
-#define _UTILS_H_
-
-static inline s32 log_2_n_round_up(u32 n)
-{
-	s32 log2n = -1;
-	u32 temp = n;
-
-	while (temp) {
-		log2n++;
-		temp >>= 1;
-	}
-
-	if (n & (n - 1))
-		return log2n + 1; /* not power of 2 - round up */
-	else
-		return log2n; /* power of 2 */
-}
-
-static inline s32 log_2_n_round_down(u32 n)
-{
-	s32 log2n = -1;
-	u32 temp = n;
-
-	while (temp) {
-		log2n++;
-		temp >>= 1;
-	}
-
-	return log2n;
-}
-
-#endif
diff --git a/src/arch/x86/include/arch/io.h b/src/arch/x86/include/arch/io.h
index ce9477358a..5c85019daf 100644
--- a/src/arch/x86/include/arch/io.h
+++ b/src/arch/x86/include/arch/io.h
@@ -174,8 +174,8 @@ static inline __attribute__((always_inline)) void write32(volatile void *addr, u
 }
 
 /* Conflicts with definition in lib.h */
-#if defined(__ROMCC__) || defined(__SMM__)
-static inline int log2(int value)
+#if defined(__ROMCC__)
+static inline int log2(u32 value)
 {
         unsigned int r = 0;
         __asm__ volatile (
@@ -187,10 +187,8 @@ static inline int log2(int value)
         return r;
 
 }
-#endif
 
-#if defined(__PRE_RAM__) || defined(__SMM__)
-static inline int log2f(int value)
+static inline int __ffs(u32 value)
 {
         unsigned int r = 0;
         __asm__ volatile (
diff --git a/src/include/lib.h b/src/include/lib.h
index 7ad33dd552..b81b1b18bb 100644
--- a/src/include/lib.h
+++ b/src/include/lib.h
@@ -24,12 +24,6 @@
 #include <stdint.h>
 #include <types.h>
 
-#if !defined(__ROMCC__) /* Conflicts with inline function in arch/io.h */
-/* Defined in src/lib/clog2.c */
-unsigned long log2(unsigned long x);
-#endif
-unsigned long log2_ceil(unsigned long x);
-
 /* Defined in src/lib/lzma.c */
 unsigned long ulzma(unsigned char *src, unsigned char *dst);
 
@@ -49,4 +43,16 @@ int checkstack(void *top_of_stack, int core);
 void hexdump(const void *memory, size_t length);
 void hexdump32(char LEVEL, const void *d, size_t len);
 
+#if !defined(__ROMCC__)
+/* Count Leading Zeroes: clz(0) == 32, clz(0xf) == 28, clz(1 << 31) == 0 */
+static inline int clz(u32 x) { return x ? __builtin_clz(x) : sizeof(x) * 8; }
+/* Integer binary logarithm (rounding down): log2(0) == -1, log2(5) == 2 */
+static inline int log2(u32 x) { return sizeof(x) * 8 - clz(x) - 1; }
+/* Find First Set: __ffs(1) == 0, __ffs(0) == -1, __ffs(1<<31) == 31 */
+static inline int __ffs(u32 x) { return log2(x & (u32)(-(s32)x)); }
+#endif
+
+/* Integer binary logarithm (rounding up): log2_ceil(0) == -1, log2(5) == 3 */
+static inline int log2_ceil(u32 x) { return (x == 0) ? -1 : log2(x * 2 - 1); }
+
 #endif /* __LIB_H__ */
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index 557cd66846..76c8fd3dc5 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -25,7 +25,7 @@ bootblock-y += cbfs.c
 bootblock-y += cbfs_boot_props.c
 bootblock-$(CONFIG_COMMON_CBFS_SPI_WRAPPER) += cbfs_spi.c
 bootblock-$(CONFIG_GENERIC_GPIO_LIB) += gpio.c
-
+bootblock-y += libgcc.c
 bootblock-$(CONFIG_GENERIC_UDELAY) += timer.c
 
 bootblock-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
@@ -45,6 +45,7 @@ verstage-y += cbfs.c
 verstage-y += halt.c
 verstage-y += fmap.c
 verstage-y += cbfs_boot_props.c
+verstage-y += libgcc.c
 verstage-y += memcmp.c
 verstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
 verstage-y += region.c
@@ -77,6 +78,7 @@ romstage-y += cbfs.c
 romstage-y += cbfs_boot_props.c
 romstage-$(CONFIG_COMMON_CBFS_SPI_WRAPPER) += cbfs_spi.c
 romstage-$(CONFIG_COMPRESS_RAMSTAGE) += lzma.c lzmadecode.c
+romstage-y += libgcc.c
 romstage-$(CONFIG_PRIMITIVE_MEMTEST) += primitive_memtest.c
 ramstage-$(CONFIG_PRIMITIVE_MEMTEST) += primitive_memtest.c
 romstage-$(CONFIG_CACHE_AS_RAM) += ramtest.c
@@ -115,8 +117,6 @@ ramstage-y += cbfs_boot_props.c
 ramstage-$(CONFIG_COMMON_CBFS_SPI_WRAPPER) += cbfs_spi.c
 ramstage-y += lzma.c lzmadecode.c
 ramstage-y += stack.c
-ramstage-y += clog2.c
-romstage-y += clog2.c
 ramstage-$(CONFIG_CONSOLE_CBMEM) += cbmem_console.c
 ramstage-$(CONFIG_BOOTSPLASH) += jpeg.c
 ramstage-$(CONFIG_TRACE) += trace.c
diff --git a/src/lib/clog2.c b/src/lib/clog2.c
deleted file mode 100644
index 5e0d591de4..0000000000
--- a/src/lib/clog2.c
+++ /dev/null
@@ -1,37 +0,0 @@
-#include <console/console.h>
-#include <lib.h>
-
-/* Assume 8 bits per byte */
-#define CHAR_BIT 8
-
-unsigned long log2(unsigned long x)
-{
-	/* assume 8 bits per byte. */
-	unsigned long pow = sizeof(x) * CHAR_BIT - 1ULL;
-	unsigned long i = 1ULL << pow;
-
-	if (!x) {
-		printk(BIOS_WARNING, "%s called with invalid parameter of 0\n",
-			__func__);
-		return -1;
-	}
-
-	for (; i > x; i >>= 1, pow--);
-
-	return pow;
-}
-
-unsigned long log2_ceil(unsigned long x)
-{
-	unsigned long pow;
-
-	if (!x)
-		return -1;
-
-	pow = log2(x);
-
-	if (x > (1ULL << pow))
-		pow++;
-
-	return pow;
-}
diff --git a/src/lib/libgcc.c b/src/lib/libgcc.c
new file mode 100644
index 0000000000..14685becf0
--- /dev/null
+++ b/src/lib/libgcc.c
@@ -0,0 +1,56 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc.
+ */
+
+#include <types.h>
+
+/*
+ * Provide platform-independent backend implementation for __builtin_clz() in
+ * <lib.h> in case GCC does not have an assembly version for this arch.
+ */
+
+#if !IS_ENABLED(CONFIG_ARCH_X86) /* work around lack of --gc-sections on x86 */
+int __clzsi2(u32 a);
+int __clzsi2(u32 a)
+{
+	static const u8 four_bit_table[] = {
+		[0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
+		[0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
+		[0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
+		[0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
+	};
+	int r = 0;
+
+	if (!(a & (0xffff << 16))) {
+		r += 16;
+		a <<= 16;
+	}
+
+	if (!(a & (0xff << 24))) {
+		r += 8;
+		a <<= 8;
+	}
+
+	if (!(a & (0xf << 28))) {
+		r += 4;
+		a <<= 4;
+	}
+
+	return r + four_bit_table[a >> 28];
+}
+#endif
diff --git a/src/northbridge/amd/amdk8/coherent_ht.c b/src/northbridge/amd/amdk8/coherent_ht.c
index a8d87008f5..6554e075ea 100644
--- a/src/northbridge/amd/amdk8/coherent_ht.c
+++ b/src/northbridge/amd/amdk8/coherent_ht.c
@@ -66,6 +66,7 @@
 #include <device/pci_def.h>
 #include <device/pci_ids.h>
 #include <device/hypertransport_def.h>
+#include <lib.h>
 #include <stdlib.h>
 #include <arch/io.h>
 #include <pc80/mc146818rtc.h>
diff --git a/src/northbridge/amd/amdk8/raminit.c b/src/northbridge/amd/amdk8/raminit.c
index 4213cfb3a2..c58abb15ae 100644
--- a/src/northbridge/amd/amdk8/raminit.c
+++ b/src/northbridge/amd/amdk8/raminit.c
@@ -7,6 +7,7 @@
 #include <cpu/x86/cache.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/amd/mtrr.h>
+#include <lib.h>
 #include <stdlib.h>
 #include <arch/acpi.h>
 #include <reset.h>
@@ -1655,7 +1656,7 @@ static struct spd_set_memclk_result spd_set_memclk(const struct mem_controller *
 	/* if the next lower frequency gives a CL at least one whole cycle
 	 * shorter, select that (see end of BKDG 4.1.1.1) */
 	if (freq < sizeof(cl_at_freq)-1 && cl_at_freq[freq+1] &&
-		log2f(cl_at_freq[freq]) - log2f(cl_at_freq[freq+1]) >= 2)
+		__ffs(cl_at_freq[freq]) - __ffs(cl_at_freq[freq+1]) >= 2)
 			freq++;
 
 	if (freq == sizeof(cl_at_freq))
@@ -1690,7 +1691,7 @@ static struct spd_set_memclk_result spd_set_memclk(const struct mem_controller *
 	/* Update DRAM Timing Low with our selected cas latency */
 	value = pci_read_config32(ctrl->f2, DRAM_TIMING_LOW);
 	value &= ~(DTL_TCL_MASK << DTL_TCL_SHIFT);
-	value |= latencies[log2f(cl_at_freq[freq]) - 2] << DTL_TCL_SHIFT;
+	value |= latencies[__ffs(cl_at_freq[freq]) - 2] << DTL_TCL_SHIFT;
 	pci_write_config32(ctrl->f2, DRAM_TIMING_LOW, value);
 
 	result.dimm_mask = dimm_mask;
diff --git a/src/northbridge/amd/amdk8/raminit_f.c b/src/northbridge/amd/amdk8/raminit_f.c
index 14696846dc..1c1a6ea142 100644
--- a/src/northbridge/amd/amdk8/raminit_f.c
+++ b/src/northbridge/amd/amdk8/raminit_f.c
@@ -25,6 +25,7 @@
 #include <cpu/x86/tsc.h>
 #include <cpu/amd/mtrr.h>
 
+#include <lib.h>
 #include <stdlib.h>
 #include <arch/acpi.h>
 #include "raminit.h"
diff --git a/src/northbridge/amd/amdk8/raminit_test.c b/src/northbridge/amd/amdk8/raminit_test.c
index be46f27bca..87e281d645 100644
--- a/src/northbridge/amd/amdk8/raminit_test.c
+++ b/src/northbridge/amd/amdk8/raminit_test.c
@@ -1,5 +1,6 @@
 #include <unistd.h>
 #include <limits.h>
+#include <lib.h>
 #include <stdint.h>
 #include <string.h>
 #include <setjmp.h>
diff --git a/src/northbridge/intel/e7501/raminit.c b/src/northbridge/intel/e7501/raminit.c
index f4fc9a8a77..93a3a5b5a9 100644
--- a/src/northbridge/intel/e7501/raminit.c
+++ b/src/northbridge/intel/e7501/raminit.c
@@ -12,6 +12,7 @@
 /* converted to C 6/2004 yhlu */
 
 #include <assert.h>
+#include <lib.h>
 #include <spd.h>
 #include <sdram_mode.h>
 #include <stdlib.h>
diff --git a/src/northbridge/intel/i3100/raminit_ep80579.c b/src/northbridge/intel/i3100/raminit_ep80579.c
index 85660e9c08..ee8c4fd7f7 100644
--- a/src/northbridge/intel/i3100/raminit_ep80579.c
+++ b/src/northbridge/intel/i3100/raminit_ep80579.c
@@ -22,6 +22,7 @@
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/cache.h>
 #include <cpu/intel/speedstep.h>
+#include <lib.h>
 #include "raminit_ep80579.h"
 #include "ep80579.h"
 
diff --git a/src/northbridge/intel/i855/raminit.c b/src/northbridge/intel/i855/raminit.c
index 81dcbb507c..a43f5be6b7 100644
--- a/src/northbridge/intel/i855/raminit.c
+++ b/src/northbridge/intel/i855/raminit.c
@@ -19,6 +19,7 @@
  */
 
 #include <assert.h>
+#include <lib.h>
 #include <spd.h>
 #include <sdram_mode.h>
 #include <stdlib.h>
diff --git a/src/northbridge/intel/i945/raminit.c b/src/northbridge/intel/i945/raminit.c
index a3be6803f0..7bd62402b6 100644
--- a/src/northbridge/intel/i945/raminit.c
+++ b/src/northbridge/intel/i945/raminit.c
@@ -20,6 +20,7 @@
 #include <console/console.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/cache.h>
+#include <lib.h>
 #include <pc80/mc146818rtc.h>
 #include <spd.h>
 #include <string.h>
diff --git a/src/soc/rockchip/rk3288/clock.c b/src/soc/rockchip/rk3288/clock.c
index 2c56376b04..a2e8d88ef3 100644
--- a/src/soc/rockchip/rk3288/clock.c
+++ b/src/soc/rockchip/rk3288/clock.c
@@ -21,6 +21,7 @@
 #include <assert.h>
 #include <console/console.h>
 #include <delay.h>
+#include <lib.h>
 #include <soc/addressmap.h>
 #include <soc/clock.h>
 #include <soc/grf.h>
@@ -236,22 +237,6 @@ static int rkclk_set_pll(u32 *pll_con, const struct pll_div *div)
 	return 0;
 }
 
-/*
-    TODO:
-    it should be replaced by lib.h function
-   'unsigned long log2(unsigned long x)'
-*/
-static unsigned int log2(unsigned int value)
-{
-	unsigned int div = 0;
-
-	while (value != 1) {
-		div++;
-		value = ALIGN_UP(value, 2) / 2;
-	}
-	return div;
-}
-
 void rkclk_init(void)
 {
 	u32 aclk_div;
diff --git a/src/southbridge/via/k8t890/traf_ctrl.c b/src/southbridge/via/k8t890/traf_ctrl.c
index b4620da4ff..24c1e65707 100644
--- a/src/southbridge/via/k8t890/traf_ctrl.c
+++ b/src/southbridge/via/k8t890/traf_ctrl.c
@@ -24,10 +24,9 @@
 #include <arch/acpi.h>
 #include <arch/acpigen.h>
 #include <cpu/amd/powernow.h>
+#include <lib.h>
 #include "k8t890.h"
 
-extern unsigned long log2(unsigned long x);
-
 static void mmconfig_set_resources(device_t dev)
 {
 	struct resource *resource;