linux-kernel - Re: [PATCH] w1: omap-hdq: Simplify driver with PM runtime autosuspend

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Date:   Sun, 15 Dec 2019 23:03:31 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Evgeniy Polyakov <zbr@...emap.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        Adam Ford <aford173@...il.com>,
        "Andrew F . Davis" <afd@...com>,
        "H . Nikolaus Schaller" <hns@...delico.com>,
        Vignesh R <vigneshr@...com>
Subject: Re: [PATCH] w1: omap-hdq: Simplify driver with PM runtime
 autosuspend

On Sun, 15 Dec 2019 09:38:17 -0800
Tony Lindgren <tony@...mide.com> wrote:

> We've had generic code handling module sysconfig and OCP reset registers
> for omap variants for many years now and all the drivers really needs to
> do is just call runtime PM functions.
> 
> Looks like the omap-hdq driver got only partially updated over the years
> to use runtime PM, and still has lots of custom PM code left.
> 
> We can replace all the custom code for sysconfig, OCP reset, and PM with
> just a few lines of runtime PM autosuspend code.
> 
> Note that the earlier driver specific usage count limit of four seems
> completely artificial and should not be an issue in normal use.
> 
> Cc: Adam Ford <aford173@...il.com>
> Cc: Andrew F. Davis <afd@...com>
> Cc: Andreas Kemnade <andreas@...nade.info>
> Cc: H. Nikolaus Schaller <hns@...delico.com>
> Cc: Vignesh R <vigneshr@...com>
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
> 
> 
> Can you guys please review and and test on gta04 and torpedo?
> 
[...]
>  
> -static int _omap_hdq_reset(struct hdq_data *hdq_data)
> -{
> -	int ret;
> -	u8 tmp_status;
> -
> -	hdq_reg_out(hdq_data, OMAP_HDQ_SYSCONFIG,
> -		    OMAP_HDQ_SYSCONFIG_SOFTRESET);
> -	/*
> -	 * Select HDQ/1W mode & enable clocks.
> -	 * It is observed that INT flags can't be cleared via a read and GO/INIT
> -	 * won't return to zero if interrupt is disabled. So we always enable
> -	 * interrupt.
> -	 */

If I remember correctly this thing is critical to get the hwmod out of
reset but I need to examine that again:

> -	hdq_reg_out(hdq_data, OMAP_HDQ_CTRL_STATUS,
> -		OMAP_HDQ_CTRL_STATUS_CLOCKENABLE |
> -		OMAP_HDQ_CTRL_STATUS_INTERRUPTMASK);
> -
> -	/* wait for reset to complete */
> -	ret = hdq_wait_for_flag(hdq_data, OMAP_HDQ_SYSSTATUS,
> -		OMAP_HDQ_SYSSTATUS_RESETDONE, OMAP_HDQ_FLAG_SET, &tmp_status);
> -	if (ret)
> -		dev_dbg(hdq_data->dev, "timeout waiting HDQ reset, %x",
> -				tmp_status);
> -	else {
> -		hdq_reg_out(hdq_data, OMAP_HDQ_CTRL_STATUS,
> -			OMAP_HDQ_CTRL_STATUS_CLOCKENABLE |
> -			OMAP_HDQ_CTRL_STATUS_INTERRUPTMASK |
> -			hdq_data->mode);
> -		hdq_reg_out(hdq_data, OMAP_HDQ_SYSCONFIG,
> -			OMAP_HDQ_SYSCONFIG_AUTOIDLE);
> -	}
> -
> -	return ret;
> -}

I will probably do more testing the next days.

Regards,
Andreas