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From: Arnd Bergmann <arnd@arndb.de>
To: Guo Ren <ren_guo@c-sky.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	David Miller <davem@davemloft.net>,
	gregkh <gregkh@linuxfoundation.org>,
	Christoph Hellwig <hch@infradead.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Rob Herring <robh@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	DTML <devicetree@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	c-sky_gcc_upstream@c-sky.com, linfei_chen@c-sky.com,
	Mao Han <han_mao@c-sky.com>
Subject: Re: [PATCH V9 13/21] csky: Library functions
Date: Wed, 17 Oct 2018 17:24:36 +0200	[thread overview]
Message-ID: <CAK8P3a3hJ+Xt2xfTg=bkDBfahk7Z-3+Unt1MqmMQrRnCeJhVtg@mail.gmail.com> (raw)
In-Reply-To: <f884af8fffa1645c2650292a3001a2fbfc4cc390.1539655732.git.ren_guo@c-sky.com>

On Tue, Oct 16, 2018 at 5:02 AM Guo Ren <ren_guo@c-sky.com> wrote:

> +++ b/arch/csky/lib/delay.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/delay.h>
> +
> +void __delay(unsigned long loops)
> +{
> +       asm volatile (
> +               "mov r0, r0\n"
> +               "1:declt %0\n"
> +               "bf     1b"
> +               : "=r"(loops)
> +               : "0"(loops));
> +}
> +EXPORT_SYMBOL(__delay);
> +
> +void __const_udelay(unsigned long xloops)
> +{
> +       unsigned long long loops;
> +
> +       loops = (unsigned long long)xloops * loops_per_jiffy * HZ;
> +
> +       __delay(loops >> 32);
> +}
> +EXPORT_SYMBOL(__const_udelay);

I can't find any indication we discussed this part before. Can you
explain (in the
changelog and in a reply) if there is a reliable high-resolution clocksource
available in the architecture? If you can read the elapsed time here instead of
using the loops_per_jiffy estimate, that would make this more robust, as
well as speed up the boot.

If you can't do that in general, that's fine, and you can add my
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

  reply	other threads:[~2018-10-17 15:24 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-16  2:58 [PATCH V9 00/21] C-SKY(csky) Linux Kernel Port Guo Ren
2018-10-16  2:58 ` [PATCH V9 01/21] csky: Build infrastructure Guo Ren
2018-10-23  0:08   ` Guo Ren
2018-10-24 22:53     ` Arnd Bergmann
2018-10-25 17:04       ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 02/21] csky: defconfig Guo Ren
2018-10-17 14:56   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 03/21] csky: Kernel booting Guo Ren
2018-10-17 14:58   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 04/21] csky: Exception handling and mm-fault Guo Ren
2018-10-17 14:59   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 05/21] csky: System Call Guo Ren
2018-10-17 15:02   ` Arnd Bergmann
2018-10-18  2:02     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 06/21] csky: Cache and TLB routines Guo Ren
2018-10-17 15:08   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 07/21] csky: MMU and page table management Guo Ren
2018-10-17 15:06   ` Arnd Bergmann
2018-10-18  2:05     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 08/21] csky: Process management and Signal Guo Ren
2018-10-17 15:11   ` Arnd Bergmann
2018-10-18  2:37     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 09/21] csky: VDSO and rt_sigreturn Guo Ren
2018-10-17 15:13   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 10/21] csky: IRQ handling Guo Ren
2018-10-17 15:14   ` Arnd Bergmann
2018-10-18  2:39     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 11/21] csky: Atomic operations Guo Ren
2018-10-17 15:17   ` Arnd Bergmann
2018-10-18  2:40     ` Guo Ren
2018-10-21 20:55   ` Peter Zijlstra
2018-10-22  1:52     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 12/21] csky: ELF and module probe Guo Ren
2018-10-17 15:18   ` Arnd Bergmann
2018-10-18  2:49     ` Guo Ren
2018-10-18  8:31       ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 13/21] csky: Library functions Guo Ren
2018-10-17 15:24   ` Arnd Bergmann [this message]
2018-10-18  3:10     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 14/21] csky: User access Guo Ren
2018-10-17 15:37   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 15/21] csky: Debug and Ptrace GDB Guo Ren
2018-10-17 15:46   ` Arnd Bergmann
2018-10-18  3:17     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 16/21] csky: SMP support Guo Ren
2018-10-17 15:47   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 17/21] csky: Misc headers Guo Ren
2018-10-17 15:49   ` Arnd Bergmann
2018-10-16  2:58 ` [PATCH V9 18/21] dt-bindings: csky CPU Bindings Guo Ren
2018-10-17 15:50   ` Arnd Bergmann
2018-10-18  3:21     ` Guo Ren
2018-10-18  3:45       ` Guo Ren
2018-10-18 14:31   ` Rob Herring
2018-10-19  2:19     ` Guo Ren
2018-10-16  2:58 ` [PATCH V9 19/21] dt-bindings: Add vendor prefix for csky Guo Ren
2018-10-16  2:58 ` [PATCH V9 20/21] MAINTAINERS: Add csky Guo Ren
2018-10-17 15:51   ` Arnd Bergmann
2018-10-16  5:48 ` [PATCH V9 21/21] csky: support dword access for get_user_size() Guo Ren
2018-10-17 15:44   ` Arnd Bergmann
2018-10-18  3:41     ` Guo Ren
2018-10-18  8:34       ` Arnd Bergmann
2018-10-18  8:57         ` Guo Ren
2018-10-24  7:17           ` Arnd Bergmann
2018-10-25 17:08             ` Guo Ren
2018-10-17 15:58 ` [PATCH V9 00/21] C-SKY(csky) Linux Kernel Port Arnd Bergmann
2018-10-18  4:10   ` Guo Ren
2018-10-18  8:36     ` Arnd Bergmann
2018-10-18  9:03       ` Guo Ren

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