linux-kernel - Re: [PATCH 1/1] Clocksource: Move the Hyper-V clocksource driver out of staging

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Date:	Mon, 23 May 2011 11:40:27 -0700
From:	john stultz <johnstul@...ibm.com>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, tglx@...utronix.de,
	hch@...radead.org, Hank Janssen <hjanssen@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: Re: [PATCH 1/1] Clocksource: Move the Hyper-V clocksource driver
 out of staging

On Mon, 2011-05-23 at 10:12 -0700, K. Y. Srinivasan wrote:
> Move the Hyper-V clocksource driver out of staging.
> 
> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> Signed-off-by: Hank Janssen <hjanssen@...rosoft.com>
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> ---
>  drivers/clocksource/Makefile        |    1 +
>  drivers/clocksource/hv_timesource.c |  102 +++++++++++++++++++++++++++++++++++
>  drivers/staging/hv/Makefile         |    2 +-
>  drivers/staging/hv/hv_timesource.c  |  102 -----------------------------------
>  4 files changed, 104 insertions(+), 103 deletions(-)
>  create mode 100644 drivers/clocksource/hv_timesource.c
>  delete mode 100644 drivers/staging/hv/hv_timesource.c
> 
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index be61ece..ea44327 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -6,3 +6,4 @@ obj-$(CONFIG_CS5535_CLOCK_EVENT_SRC)	+= cs5535-clockevt.o
>  obj-$(CONFIG_SH_TIMER_CMT)	+= sh_cmt.o
>  obj-$(CONFIG_SH_TIMER_MTU2)	+= sh_mtu2.o
>  obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
> +obj-$(CONFIG_HYPERV)		+= hv_timesource.o
> diff --git a/drivers/clocksource/hv_timesource.c b/drivers/clocksource/hv_timesource.c
> new file mode 100644
> index 0000000..0efb049
> --- /dev/null
> +++ b/drivers/clocksource/hv_timesource.c
> @@ -0,0 +1,102 @@
> +/*
> + * A clocksource for Linux running on HyperV.
> + *
> + *
> + * Copyright (C) 2010, Novell, Inc.
> + * Author : K. Y. Srinivasan <ksrinivasan@...ell.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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, GOOD TITLE or
> + * NON INFRINGEMENT.  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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
> + *
> + */
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/version.h>
> +#include <linux/clocksource.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/dmi.h>
> +#include <asm/hyperv.h>
> +#include <asm/mshyperv.h>
> +#include <asm/hypervisor.h>
> +
> +#define HV_CLOCK_SHIFT	22
> +
> +static cycle_t read_hv_clock(struct clocksource *arg)
> +{
> +	cycle_t current_tick;
> +	/*
> +	 * Read the partition counter to get the current tick count. This count
> +	 * is set to 0 when the partition is created and is incremented in
> +	 * 100 nanosecond units.
> +	 */
> +	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> +	return current_tick;
> +}
> +
> +static struct clocksource hyperv_cs = {
> +	.name           = "hyperv_clocksource",
> +	.rating         = 400, /* use this when running on Hyperv*/
> +	.read           = read_hv_clock,
> +	.mask           = CLOCKSOURCE_MASK(64),
> +	/*
> +	 * The time ref counter in HyperV is in 100ns units.
> +	 * The definition of mult is:
> +	 * mult/2^shift = ns/cyc = 100
> +	 * mult = (100 << shift)
> +	 */
> +	.mult           = (100 << HV_CLOCK_SHIFT),
> +	.shift          = HV_CLOCK_SHIFT,

The mult/shift assignments can be dropped. Please use
clocksource_register_hz/khz() which will assign mult/shift for you.

Otherwise it looks pretty straightforward. 


> +module_init(init_hv_clocksource);
> +MODULE_DESCRIPTION("HyperV based clocksource");
> +MODULE_AUTHOR("K. Y. Srinivasan <ksrinivasan@...ell.com>");
> +MODULE_LICENSE("GPL");

One other nit: Should this email address be updated to your current one?

thanks
-john


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