Re: [patch 06/38] calibrate: Rework delay timer calibration
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From: Jon Hunter <jonathanh@nvidia.com>
Date: 2026-08-20 16:12:57
Also in:
linux-alpha, linux-crypto, linux-ext4, linux-fbdev, linux-hams, linux-iommu, linux-m68k, linux-mm, linux-riscv, linux-s390, linux-tegra, linux-wireless, linuxppc-dev, lkml, loongarch, sparclinux
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Hi Thomas, On 10/04/2026 13:18, Thomas Gleixner wrote:
The header define in asm/timex,h and the naming of the function to read the delay timer are confusing at best. Convert it to a config switch selected by the archictures, which provide the functionality, and rename the function to delay_read_timer(), which makes the purpose clear. Move the declaration to linux/delay.h where it belongs. Remove the resulting empty asm/timex.h files as well. No functional change. Signed-off-by: Thomas Gleixner <tglx@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de>
...
quoted hunk ↗ jump to hunk
--- a/arch/arm/include/asm/timex.h +++ b/arch/arm/include/asm/timex.h@@ -10,7 +10,10 @@ #define _ASMARM_TIMEX_H typedef unsigned long cycles_t; -#define get_cycles() ({ cycles_t c; read_current_timer(&c) ? 0 : c; }) +// Temporary workaround +bool delay_read_timer(unsigned long *t); + +#define get_cycles() ({ cycles_t c; delay_read_timer(&c) ? 0 : c; }) #define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
I have noticed a boot regression on some of our 32-bit Tegra platforms. Bisect is pointing to this commit. Making the following change does fix it, as delay_read_timer() now returns a valid value when true ...
diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
index 94e40c19cfc5..4d31eab9dba2 100644
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h@@ -13,7 +13,7 @@ typedef unsigned long cycles_t; // Temporary workaround until timex.h is cleaned up bool delay_read_timer(unsigned long *t); -#define get_cycles() ({ cycles_t c; delay_read_timer(&c) ? 0 : c; }) +#define get_cycles() ({ cycles_t c; delay_read_timer(&c) ? c : 0; }) #define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
Cheers Jon -- nvpublic