linux-kernel - Re: [PATCH 09/14] bus: ti-sysc: Move rstctrl reset to happen later

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Message-ID: <b6bd2b04-00b4-6730-4401-6ac95e75322a@ti.com>
Date:   Tue, 26 Mar 2019 18:22:38 -0500
From:   Suman Anna <s-anna@...com>
To:     Tony Lindgren <tony@...mide.com>, <linux-omap@...r.kernel.org>
CC:     Dave Gerlach <d-gerlach@...com>, Faiz Abbas <faiz_abbas@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Keerthy <j-keerthy@...com>, Nishanth Menon <nm@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Roger Quadros <rogerq@...com>, Tero Kristo <t-kristo@...com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 09/14] bus: ti-sysc: Move rstctrl reset to happen later

Hi Tony,

On 3/26/19 6:13 PM, Tony Lindgren wrote:
> * Tony Lindgren <tony@...mide.com> [190325 22:00]:
>> We should not do the reset until the clocks are enabled. Let's only init
>> restctrl in sysc_init_resets() and do the reset later on in sysc_reset().
> ...
> 
>>  static int sysc_reset(struct sysc *ddata)
>>  {
>>  	int offset = ddata->offsets[SYSC_SYSCONFIG];
>> -	int val;
>> +	int error, val;
>>  
>>  	if (ddata->legacy_mode || offset < 0 ||
>>  	    ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT)
>> -		return 0;
>> +		return sysc_rstctrl_reset_deassert(ddata, false);
>> +
>> +	error = sysc_rstctrl_reset_deassert(ddata, true);
>> +	if (error)
>> +		return error;
> 
> This change is wrong, we need to deassert rstctrl reset before
> we enable clocks, not after. Updated version below.

Hmm, are you envisioning the SYSC reset (OCP SoftReset) here or the PRCM
RSTCTRL hardresets here? The latter in general requires the clocks to be
running first (module won't be in ready status until you deassert the
hardresets with clocks running). You can look up the Warm-reset or
Cold-reset sequences in the TRMs for any of the processors.

I am working on preparing the next version of PRUSS patches with ti-sysc
on AM33xx/AM437x/AM57xx platforms, so will pick up these patches for my
testing.

regards
Suman

> 
> Regards,
> 
> Tony
> 
> 8< --------------------
> From tony Mon Sep 17 00:00:00 2001
> From: Tony Lindgren <tony@...mide.com>
> Date: Thu, 21 Mar 2019 11:00:21 -0700
> Subject: [PATCH] bus: ti-sysc: Move rstctrl reset to happen later
> 
> We can do the rsstctrl a bit later, but need to deassert rstctrl reset
> before the clocks are enabled if asserted. Let's only init restctrl
> in sysc_init_resets() and do the reset later on just before we enable
> the device clocks.
> 
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
>  drivers/bus/ti-sysc.c | 61 +++++++++++++++++++++++++++----------------
>  1 file changed, 39 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c
> --- a/drivers/bus/ti-sysc.c
> +++ b/drivers/bus/ti-sysc.c
> @@ -339,38 +339,18 @@ static void sysc_disable_opt_clocks(struct sysc *ddata)
>  }
>  
>  /**
> - * sysc_init_resets - reset module on init
> + * sysc_init_resets - init rstctrl reset line if configured
>   * @ddata: device driver data
>   *
> - * A module can have both OCP softreset control and external rstctrl.
> - * If more complicated rstctrl resets are needed, please handle these
> - * directly from the child device driver and map only the module reset
> - * for the parent interconnect target module device.
> - *
> - * Automatic reset of the module on init can be skipped with the
> - * "ti,no-reset-on-init" device tree property.
> + * See sysc_rstctrl_reset_deassert().
>   */
>  static int sysc_init_resets(struct sysc *ddata)
>  {
> -	int error;
> -
>  	ddata->rsts =
>  		devm_reset_control_array_get_optional_exclusive(ddata->dev);
>  	if (IS_ERR(ddata->rsts))
>  		return PTR_ERR(ddata->rsts);
>  
> -	if (ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT)
> -		goto deassert;
> -
> -	error = reset_control_assert(ddata->rsts);
> -	if (error)
> -		return error;
> -
> -deassert:
> -	error = reset_control_deassert(ddata->rsts);
> -	if (error)
> -		return error;
> -
>  	return 0;
>  }
>  
> @@ -1031,6 +1011,35 @@ static int sysc_legacy_init(struct sysc *ddata)
>  	return error;
>  }
>  
> +/**
> + * sysc_rstctrl_reset_deassert - deassert rstctrl reset
> + * @ddata: device driver data
> + * @reset: reset before deassert
> + *
> + * A module can have both OCP softreset control and external rstctrl.
> + * If more complicated rstctrl resets are needed, please handle these
> + * directly from the child device driver and map only the module reset
> + * for the parent interconnect target module device.
> + *
> + * Automatic reset of the module on init can be skipped with the
> + * "ti,no-reset-on-init" device tree property.
> + */
> +static int sysc_rstctrl_reset_deassert(struct sysc *ddata, bool reset)
> +{
> +	int error;
> +
> +	if (!ddata->rsts)
> +		return 0;
> +
> +	if (reset) {
> +		error = reset_control_assert(ddata->rsts);
> +		if (error)
> +			return error;
> +	}
> +
> +	return reset_control_deassert(ddata->rsts);
> +}
> +
>  static int sysc_reset(struct sysc *ddata)
>  {
>  	int offset = ddata->offsets[SYSC_SYSCONFIG];
> @@ -1071,6 +1080,14 @@ static int sysc_init_module(struct sysc *ddata)
>  {
>  	int error = 0;
>  	bool manage_clocks = true;
> +	bool reset = true;
> +
> +	if (ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT)
> +		reset = false;
> +
> +	error = sysc_rstctrl_reset_deassert(ddata, reset);
> +	if (error)
> +		return error;
>  
>  	if (ddata->cfg.quirks &
>  	    (SYSC_QUIRK_NO_IDLE | SYSC_QUIRK_NO_IDLE_ON_INIT))
>