[patch 28/38] mips: Select ARCH_HAS_RANDOM_ENTROPY

Thomas Gleixner
2026-04-10T12:21:15Z

The only remaining usage of get_cycles() is to provide random_get_entropy().

Switch mips over to the new scheme of selecting ARCH_HAS_RANDOM_ENTROPY
and providing random_get_entropy() in asm/random.h.

As a consequence this unearthed a nasty include dependency hell because
arbitrary code relies on a magic include of asm/timex.h. Including the
headers in asm/random.h turned out to be impossible as well.

The only solution for now is to uninline random_get_entropy(). Fix up all
other dependencies on the content of asm/timex.h in those files which
really depend on it.

Remove asm/timex.h as it has no functionality anymore.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
---
arch/mips/Kconfig | 1
arch/mips/generic/init.c | 1
arch/mips/include/asm/random.h | 7 +++
arch/mips/include/asm/timex.h | 92 -----------------------------------------
arch/mips/kernel/pm-cps.c | 1
arch/mips/kernel/proc.c | 1
arch/mips/kernel/relocate.c | 1
arch/mips/kernel/time.c | 53 +++++++++++++++++++++++
arch/mips/lib/dump_tlb.c | 1
arch/mips/mm/cache.c | 1
10 files changed, 66 insertions(+), 93 deletions(-)

--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -19,6 +19,7 @@ config MIPS
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UBSAN
select ARCH_HAS_GCOV_PROFILE_ALL
+ select ARCH_HAS_RANDOM_ENTROPY
select ARCH_KEEP_MEMBLOCK
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
--- a/arch/mips/generic/init.c
+++ b/arch/mips/generic/init.c
@@ -12,6 +12,7 @@
#include <linux/of_fdt.h>

#include <asm/bootinfo.h>
+#include <asm/cpu-type.h>
#include <asm/fw/fw.h>
#include <asm/irq_cpu.h>
#include <asm/machine.h>
--- /dev/null
+++ b/arch/mips/include/asm/random.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-v2.0-only */
+#ifndef _ASM_RANDOM_H
+#define _ASM_RANDOM_H
+
+unsigned long random_get_entropy(void);
+
+#endif /* _ASM_RANDOM_H */
--- a/arch/mips/include/asm/timex.h
+++ /dev/null
@@ -1,92 +0,0 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1998, 1999, 2003 by Ralf Baechle
- * Copyright (C) 2014 by Maciej W. Rozycki
- */
-#ifndef _ASM_TIMEX_H
-#define _ASM_TIMEX_H
-
-#ifdef __KERNEL__
-
-#include <linux/compiler.h>
-
-#include <asm/cpu.h>
-#include <asm/cpu-features.h>
-#include <asm/mipsregs.h>
-#include <asm/cpu-type.h>
-
-/*
- * Standard way to access the cycle counter.
- * Currently only used on SMP for scheduling.
- *
- * Only the low 32 bits are available as a continuously counting entity.
- * But this only means we'll force a reschedule every 8 seconds or so,
- * which isn't an evil thing.
- *
- * We know that all SMP capable CPUs have cycle counters.
- */
-
-/*
- * On R4000/R4400 an erratum exists such that if the cycle counter is
- * read in the exact moment that it is matching the compare register,
- * no interrupt will be generated.
- *
- * There is a suggested workaround and also the erratum can't strike if
- * the compare interrupt isn't being used as the clock source device.
- * However for now the implementation of this function doesn't get these
- * fine details right.
- */
-static inline int can_use_mips_counter(unsigned int prid)
-{
- int comp = (prid & PRID_COMP_MASK) != PRID_COMP_LEGACY;
-
- if (__builtin_constant_p(cpu_has_counter) && !cpu_has_counter)
- return 0;
- else if (__builtin_constant_p(cpu_has_mips_r) && cpu_has_mips_r)
- return 1;
- else if (likely(!__builtin_constant_p(cpu_has_mips_r) && comp))
- return 1;
- /* Make sure we don't peek at cpu_data[0].options in the fast path! */
- if (!__builtin_constant_p(cpu_has_counter))
- asm volatile("" : "=m" (cpu_data[0].options));
- if (likely(cpu_has_counter &&
- prid > (PRID_IMP_R4000 | PRID_REV_ENCODE_44(15, 15))))
- return 1;
- else
- return 0;
-}
-
-static inline cycles_t get_cycles(void)
-{
- if (can_use_mips_counter(read_c0_prid()))
- return read_c0_count();
- else
- return 0; /* no usable counter */
-}
-#define get_cycles get_cycles
-
-/*
- * Like get_cycles - but where c0_count is not available we desperately
- * use c0_random in an attempt to get at least a little bit of entropy.
- */
-static inline unsigned long random_get_entropy(void)
-{
- unsigned int c0_random;
-
- if (can_use_mips_counter(read_c0_prid()))
- return read_c0_count();
-
- if (cpu_has_3kex)
- c0_random = (read_c0_random() >> 8) & 0x3f;
- else
- c0_random = read_c0_random() & 0x3f;
- return (random_get_entropy_fallback() << 6) | (0x3f - c0_random);
-}
-#define random_get_entropy random_get_entropy
-
-#endif /* __KERNEL__ */
-
-#endif /* _ASM_TIMEX_H */
--- a/arch/mips/kernel/pm-cps.c
+++ b/arch/mips/kernel/pm-cps.c
@@ -13,6 +13,7 @@
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/cacheops.h>
+#include <asm/cpu-type.h>
#include <asm/idle.h>
#include <asm/mips-cps.h>
#include <asm/mipsmtregs.h>
--- a/arch/mips/kernel/proc.c
+++ b/arch/mips/kernel/proc.c
@@ -11,6 +11,7 @@
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
+#include <asm/cpu-type.h>
#include <asm/idle.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -13,7 +13,6 @@
#include <asm/fw/fw.h>
#include <asm/sections.h>
#include <asm/setup.h>
-#include <asm/timex.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/libfdt.h>
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -2,6 +2,7 @@
/*
* Copyright 2001 MontaVista Software Inc.
* Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
+ * Copyright (C) 1998, 1999, 2003 by Ralf Baechle
* Copyright (c) 2003, 2004 Maciej W. Rozycki
*
* Common time service routines for MIPS machines.
@@ -21,9 +22,12 @@
#include <linux/cpufreq.h>
#include <linux/delay.h>

+#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/cpu-type.h>
#include <asm/div64.h>
+#include <asm/mipsregs.h>
+#include <asm/random.h>
#include <asm/time.h>

#ifdef CONFIG_CPU_FREQ
@@ -150,6 +154,55 @@ static __init int cpu_has_mfc0_count_bug
return 0;
}

+
+/*
+ * On R4000/R4400 an erratum exists such that if the cycle counter is
+ * read in the exact moment that it is matching the compare register,
+ * no interrupt will be generated.
+ *
+ * There is a suggested workaround and also the erratum can't strike if
+ * the compare interrupt isn't being used as the clock source device.
+ * However for now the implementation of this function doesn't get these
+ * fine details right.
+ */
+static inline int can_use_mips_counter(unsigned int prid)
+{
+ int comp = (prid & PRID_COMP_MASK) != PRID_COMP_LEGACY;
+
+ if (__builtin_constant_p(cpu_has_counter) && !cpu_has_counter)
+ return 0;
+ else if (__builtin_constant_p(cpu_has_mips_r) && cpu_has_mips_r)
+ return 1;
+ else if (likely(!__builtin_constant_p(cpu_has_mips_r) && comp))
+ return 1;
+ /* Make sure we don't peek at cpu_data[0].options in the fast path! */
+ if (!__builtin_constant_p(cpu_has_counter))
+ asm volatile("" : "=m" (cpu_data[0].options));
+ if (likely(cpu_has_counter &&
+ prid > (PRID_IMP_R4000 | PRID_REV_ENCODE_44(15, 15))))
+ return 1;
+ else
+ return 0;
+}
+
+/*
+ * Like get_cycles - but where c0_count is not available we desperately
+ * use c0_random in an attempt to get at least a little bit of entropy.
+ */
+unsigned long random_get_entropy(void)
+{
+ unsigned int c0_random;
+
+ if (can_use_mips_counter(read_c0_prid()))
+ return read_c0_count();
+
+ if (cpu_has_3kex)
+ c0_random = (read_c0_random() >> 8) & 0x3f;
+ else
+ c0_random = read_c0_random() & 0x3f;
+ return (random_get_entropy_fallback() << 6) | (0x3f - c0_random);
+}
+
void __init time_init(void)
{
plat_time_init();
--- a/arch/mips/lib/dump_tlb.c
+++ b/arch/mips/lib/dump_tlb.c
@@ -8,6 +8,7 @@
#include <linux/kernel.h>
#include <linux/mm.h>

+#include <asm/cpu-type.h>
#include <asm/hazards.h>
#include <asm/mipsregs.h>
#include <asm/mmu_context.h>
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -22,6 +22,7 @@
#include <asm/processor.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
+#include <asm/cpu-type.h>
#include <asm/setup.h>
#include <asm/pgtable.h>