linux-kernel - Re: [PATCH v1 1/3] PM / AVS: SmartReflex: disable errgen before vpbound disable

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Date:	Tue, 28 May 2013 11:45:09 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Andrii Tseglytskyi <andrii.tseglytskyi@...com>
Cc:	J Keerthy <j-keerthy@...com>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH v1 1/3] PM / AVS: SmartReflex: disable errgen before vpbound disable

Andrii Tseglytskyi <andrii.tseglytskyi@...com> writes:

> From: Nishanth Menon <nm@...com>
>
> vpboundsintr_en is available inside the IP block as an re-sycned
> version and one which is not. Due to this, there is an 1 sysclk
> cycle window where interruptz could be asserted low for 1 cycle.
                             ^^^

Is that the way the cool kidz are spelling interrupts these days?  ;)

> IF, intr_en is cleared on the exact same cycle as the irqclr, an
> additional pulse is generated which indicates for VP that
> an additional adjustment of voltage is required.
>
> This results in VP doing two voltage adjustments for the SRERR
> (based on configuration, upto 4 steps), instead of the needed
> 1 step.
> Due to the unexpected pulse from AVS which breaks the AVS-VP
> communication protocol, VP also ends up in a stuck condition by
> entering a state where VP module remains non-responsive
> to any futher AVS adjustment events. This creates the symptom
> called "TRANXDONE Timeout" scenario.
>
> By disabling errgen prior to disable of intr_en, this situation
> can be avoided.
>
> Signed-off-by: Vincent Bour <v-bour@...com>
> Signed-off-by: Leonardo Affortunati <l-affortunati@...com>
> Signed-off-by: Nishanth Menon <nm@...com>
> Signed-off-by: Andrii.Tseglytskyi <andrii.tseglytskyi@...com>

>From Documentation/SubbmittingPatches:

   "If a person was not directly involved in the preparation or handling
   of a patch but wishes to signify and record their approval of it then
   they can arrange to have an Acked-by: line added to the patch's
   changelog."

Are all of the tags above co-authors or on the delivery path?  I suspect
an Acked-by or Reviewed-by is more appropriate here.

Otherwise, patch itself looks fine.

Kevin

> ---
>  drivers/power/avs/smartreflex.c |   11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/power/avs/smartreflex.c b/drivers/power/avs/smartreflex.c
> index 6b2238b..f34d34d 100644
> --- a/drivers/power/avs/smartreflex.c
> +++ b/drivers/power/avs/smartreflex.c
> @@ -449,12 +449,17 @@ int sr_disable_errgen(struct voltagedomain *voltdm)
>  		return -EINVAL;
>  	}
>  
> -	/* Disable the interrupts of ERROR module */
> -	sr_modify_reg(sr, errconfig_offs, vpboundint_en | vpboundint_st, 0);
> -
>  	/* Disable the Sensor and errorgen */
>  	sr_modify_reg(sr, SRCONFIG, SRCONFIG_SENENABLE | SRCONFIG_ERRGEN_EN, 0);
>  
> +	/*
> +	 * Disable the interrupts of ERROR module
> +	 * NOTE: modify is a read, modify,write - an implicit OCP barrier
> +	 * which is required is present here - sequencing is critical
> +	 * at this point (after errgen is disabled, vpboundint disable)
> +	 */
> +	sr_modify_reg(sr, errconfig_offs, vpboundint_en | vpboundint_st, 0);
> +
>  	return 0;
>  }
--
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