Date:	Wed, 6 Jul 2011 09:16:57 -0400
From:	Jean-François Dagenais <dagenaisj@...atest.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] w1: ds1wm: add a reset recovery parameter

On Jul 5, 2011, at 17:46, Andrew Morton wrote:

> On Mon, 27 Jun 2011 09:17:58 -0400
> Jean-Fran__ois Dagenais <dagenaisj@...atest.com> wrote:
> 
>> This follows the regression on 3.0 reported by Paul Parsons regarding
>> the removal of the msleep(1) in the ds1wm_reset() function. This
>> sleep should not be required on normal circuitry provided the
>> pull-ups on the bus are correctly adapted to the slaves.
>> Unfortunately, this is not always the case. The sleep is restored
>> but as a parameter to the probe function in the pdata.
> 
> A few things.
> 
> - When fixing a bug, please fully describe that bug in the changelog.
>  So that others can determine whether your patch might fix a bug
>  which they are observing.
> 
>  That's not so important when we're fixing a regression which was
>  introduced since the most recent major kernel release, but it's good
>  practice and who knows, someone might have backported the
>  regression-introducing patch.
> 
> - The patch was missing your signed-off-by.  I added it.  Please
>  ack this.
> 
> - It's conventional to give bug-reporters a hat tip via the
>  Reported-by: tag.
> 
All noted. Thanks for the constructive feedback. ds1wm mods are my first contrib to the kernel.
> Here's what I merged:
> 
> 
> From: Jean-Fran_ois Dagenais <dagenaisj@...atest.com>
If the c-cedilla doesn't work please replace the '_' by a regular 'c'... actually I will re-submit the patch as v2.
> 
> This fixes a regression on 3.0 reported by Paul Parsons regarding the
> removal of the msleep(1) in the ds1wm_reset() function:
> 
> : The linux-3.0-rc4 DS1WM 1-wire driver is logging "bus error, retrying"
> : error messages on an HP iPAQ hx4700 PDA (XScale-PXA270):
> : 
> : <snip>
> : Driver for 1-wire Dallas network protocol.
> : DS1WM w1 busmaster driver - (c) 2004 Szabolcs Gyurko
> : 1-Wire driver for the DS2760 battery monitor  chip  - (c) 2004-2005, Szabolcs Gyurko
> : ds1wm ds1wm: pass: 1 bus error, retrying
> : ds1wm ds1wm: pass: 2 bus error, retrying
> : ds1wm ds1wm: pass: 3 bus error, retrying
> : ds1wm ds1wm: pass: 4 bus error, retrying
> : ds1wm ds1wm: pass: 5 bus error, retrying
> : ...
> : 
> : The visible result is that the battery charging LED is erratic; sometimes
> : it works, mostly it doesn't.
> : 
> : The linux-2.6.39 DS1WM 1-wire driver worked OK.  I haven't tried 3.0-rc1,
> : 3.0-rc2, or 3.0-rc3.
> 
> This sleep should not be required on normal circuitry provided the
> pull-ups on the bus are correctly adapted to the slaves.  Unfortunately,
> this is not always the case.  The sleep is restored but as a parameter to
> the probe function in the pdata.
> 
> Reported-by: Paul Parsons <lost.distance@...oo.com>
> Tested-by: Paul Parsons <lost.distance@...oo.com>
> Signed-off-by: Jean-Fran_ois Dagenais <dagenaisj@...atest.com>
again, the '_' 
> Cc: Evgeniy Polyakov <johnpol@....mipt.ru>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
> drivers/mfd/asic3.c        |    1 +
> drivers/mfd/htc-pasic3.c   |    1 +
> drivers/w1/masters/ds1wm.c |    5 +++++
> include/linux/mfd/ds1wm.h  |    7 +++++++
> 4 files changed, 14 insertions(+)
> 
> diff -puN drivers/mfd/asic3.c~w1-ds1wm-add-a-reset-recovery-parameter drivers/mfd/asic3.c
> --- a/drivers/mfd/asic3.c~w1-ds1wm-add-a-reset-recovery-parameter
> +++ a/drivers/mfd/asic3.c
> @@ -619,6 +619,7 @@ static void asic3_clk_disable(struct asi
> /* MFD cells (SPI, PWM, LED, DS1WM, MMC) */
> static struct ds1wm_driver_data ds1wm_pdata = {
> 	.active_high = 1,
> +	.reset_recover_delay = 1,
> };
> 
> static struct resource ds1wm_resources[] = {
> diff -puN drivers/mfd/htc-pasic3.c~w1-ds1wm-add-a-reset-recovery-parameter drivers/mfd/htc-pasic3.c
> --- a/drivers/mfd/htc-pasic3.c~w1-ds1wm-add-a-reset-recovery-parameter
> +++ a/drivers/mfd/htc-pasic3.c
> @@ -99,6 +99,7 @@ static int ds1wm_disable(struct platform
> 
> static struct ds1wm_driver_data ds1wm_pdata = {
> 	.active_high = 0,
> +	.reset_recover_delay = 1,
> };
> 
> static struct resource ds1wm_resources[] __initdata = {
> diff -puN drivers/w1/masters/ds1wm.c~w1-ds1wm-add-a-reset-recovery-parameter drivers/w1/masters/ds1wm.c
> --- a/drivers/w1/masters/ds1wm.c~w1-ds1wm-add-a-reset-recovery-parameter
> +++ a/drivers/w1/masters/ds1wm.c
> @@ -109,6 +109,7 @@ struct ds1wm_data {
> 	/* byte to write that makes all intr disabled, */
> 	/* considering active_state (IAS) (optimization) */
> 	u8       int_en_reg_none;
> +	unsigned int reset_recover_delay; /* see ds1wm.h */
> };
> 
> static inline void ds1wm_write_register(struct ds1wm_data *ds1wm_data, u32 reg,
> @@ -187,6 +188,9 @@ static int ds1wm_reset(struct ds1wm_data
> 		return 1;
> 	}
> 
> +	if(ds1wm_data->reset_recover_delay)
> +		msleep(ds1wm_data->reset_recover_delay);
> +
> 	return 0;
> }
> 
> @@ -490,6 +494,7 @@ static int ds1wm_probe(struct platform_d
> 	}
> 	ds1wm_data->irq = res->start;
> 	ds1wm_data->int_en_reg_none = (plat->active_high ? DS1WM_INTEN_IAS : 0);
> +	ds1wm_data->reset_recover_delay = plat->reset_recover_delay;
> 
> 	if (res->flags & IORESOURCE_IRQ_HIGHEDGE)
> 		irq_set_irq_type(ds1wm_data->irq, IRQ_TYPE_EDGE_RISING);
> diff -puN include/linux/mfd/ds1wm.h~w1-ds1wm-add-a-reset-recovery-parameter include/linux/mfd/ds1wm.h
> --- a/include/linux/mfd/ds1wm.h~w1-ds1wm-add-a-reset-recovery-parameter
> +++ a/include/linux/mfd/ds1wm.h
> @@ -3,4 +3,11 @@
> struct ds1wm_driver_data {
> 	int active_high;
> 	int clock_rate;
> +	/* in milliseconds, the amount of time to */
> +	/* sleep following a reset pulse. Zero    */
> +	/* should work if your bus devices recover*/
> +	/* time respects the 1-wire spec since the*/
> +	/* ds1wm implements the precise timings of*/
> +	/* a reset pulse/presence detect sequence.*/ 
> +	unsigned int reset_recover_delay;
> };
> _
> 
>

Jean-Francois Dagenais 
Software Architect - B.Sc.A


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