linux-kernel - Re: [PATCH v2 1/2] reset: brcmstb rescal: implement {de}assert() instead of reset()

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Date:   Mon, 09 Nov 2020 11:05:37 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Jim Quinlan <james.quinlan@...adcom.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        bcm-kernel-feedback-list@...adcom.com
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Amjad Ouled-Ameur <aouledameur@...libre.com>
Subject: Re: [PATCH v2 1/2] reset: brcmstb rescal: implement {de}assert()
 instead of reset()

Hi Jim,

On Fri, 2020-11-06 at 14:17 -0500, Jim Quinlan wrote:
> Before, only control_reset() was implemented.  However, the reset core only
> invokes control_reset() once in its lifetime.  Because we need it to invoke
> control_reset() again after resume out of S2 or S3, we have switched to
> putting the reset functionality into the control_deassert() method and
> having an empty control_assert() method.
> 
> Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>

You are switching to the wrong abstraction to work around a deficiency
of the reset controller framework. Instead, it would be better to allow
to "reactivate" shared pulsed resets so they can be triggered again.

Could you please have a look at [1], which tries to implement this with
a new API call, and check if this can fix your problem? If so, it would
be great if you could coordinate with Amjad to see this fixed in the
core.

[1] https://lore.kernel.org/lkml/20201001132758.12280-1-aouledameur@baylibre.com/

regards
Philipp

> ---
>  drivers/reset/reset-brcmstb-rescal.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/reset/reset-brcmstb-rescal.c b/drivers/reset/reset-brcmstb-rescal.c
> index b6f074d6a65f..1f54ae4f91fe 100644
> --- a/drivers/reset/reset-brcmstb-rescal.c
> +++ b/drivers/reset/reset-brcmstb-rescal.c
> @@ -20,8 +20,8 @@ struct brcm_rescal_reset {
>  	struct reset_controller_dev rcdev;
>  };
>  
> -static int brcm_rescal_reset_set(struct reset_controller_dev *rcdev,
> -				 unsigned long id)
> +static int brcm_rescal_reset_deassert(struct reset_controller_dev *rcdev,
> +				unsigned long id)
>  {
>  	struct brcm_rescal_reset *data =
>  		container_of(rcdev, struct brcm_rescal_reset, rcdev);
> @@ -52,6 +52,12 @@ static int brcm_rescal_reset_set(struct reset_controller_dev *rcdev,
>  	return 0;
>  }
>  
> +static int brcm_rescal_reset_assert(struct reset_controller_dev *rcdev,
> +			      unsigned long id)
> +{
> +	return 0;
> +}
> +
>  static int brcm_rescal_reset_xlate(struct reset_controller_dev *rcdev,
>  				   const struct of_phandle_args *reset_spec)
>  {
> @@ -60,7 +66,8 @@ static int brcm_rescal_reset_xlate(struct reset_controller_dev *rcdev,
>  }
>  
>  static const struct reset_control_ops brcm_rescal_reset_ops = {
> -	.reset = brcm_rescal_reset_set,
> +	.deassert = brcm_rescal_reset_deassert,
> +	.assert = brcm_rescal_reset_assert,
>  };
>  
>  static int brcm_rescal_reset_probe(struct platform_device *pdev)