Re: [PATCH 2/2] staging: greybus: refactor arche_platform_wd_irq()

[Ira Weiny <ira.weiny@intel.com>]

Dan Carpenter wrote:
> On Thu, Mar 30, 2023 at 07:11:25PM +0500, Khadija Kamran wrote:
> > Linux kernel coding-style suggests to fix your program if it needs more
> > than 3 levels of indentation. Due to indentation, line length also
> > exceeds 100 columns, resulting in issues reported by checkpatch.
> > 
> > Refactor the arche_platform_wd_irq() function and reduce the indentation
> > with the help of goto statement.
> > 
> > Suggested-by: Alison Schofield <alison.schofield@intel.com>
> > Signed-off-by: Khadija Kamran <kamrankhadijadj@gmail.com>
> > ---
> >  drivers/staging/greybus/arche-platform.c | 79 ++++++++++++------------
> >  1 file changed, 41 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/staging/greybus/arche-platform.c b/drivers/staging/greybus/arche-platform.c
> > index a64c1af091b0..dde30c8da1a1 100644
> > --- a/drivers/staging/greybus/arche-platform.c
> > +++ b/drivers/staging/greybus/arche-platform.c
> > @@ -158,49 +158,52 @@ static irqreturn_t arche_platform_wd_irq(int irq, void *devid)
> >  
> >  	spin_lock_irqsave(&arche_pdata->wake_lock, flags);
> >  
> > -	if (gpiod_get_value(arche_pdata->wake_detect)) {
> > -		/* wake/detect rising */
> > +	if (!gpiod_get_value(arche_pdata->wake_detect))
> > +		goto falling;

I don't like this negative logic here.  Can't this be handled with
positive logic?

> >  
> > +	/* wake/detect rising */
> > +
> > +	/*
> > +	 * If wake/detect line goes high after low, within less than
> > +	 * 30msec, then standby boot sequence is initiated, which is not
> > +	 * supported/implemented as of now. So ignore it.
> > +	 */
> > +	if (arche_pdata->wake_detect_state != WD_STATE_BOOT_INIT)
> > +		goto out;
> 
> This checks that we are in WD_STATE_BOOT_INIT state.

Doesn't this check we are _not_ in WD_STATE_BOOT_INIT?

> 
> > +
> > +	if (time_before(jiffies,
> > +			arche_pdata->wake_detect_start +
> > +			msecs_to_jiffies(WD_COLDBOOT_PULSE_WIDTH_MS))) {
> > +		arche_platform_set_wake_detect_state(arche_pdata,
> > +						     WD_STATE_IDLE);
> > +		got out;
> > +	}
> > +
> > +	/* Check we are not in middle of irq thread already */
> > +	if (arche_pdata->wake_detect_state !=
> > +			WD_STATE_COLDBOOT_START) {
> 
> This checks that we are not in WD_STATE_COLDBOOT_START state.  How are
> we going to be in COLDBOOT if we are in INIT?  Is this changing in the
> background?  Can this check be removed?  This might be took tricky to
> answer but it's important that we understand this before we continue.
> 
> 
> > +		arche_platform_set_wake_detect_state(arche_pdata,
> > +						     WD_STATE_COLDBOOT_TRIG);
> > +		rc = IRQ_WAKE_THREAD;
> > +		goto out;
> > +	}
> 
> Let's assume the above check cannot be removed.
> 
> In the original code if gpiod_get_value(arche_pdata->wake_detect)
> returned true and arche_pdata->wake_detect_state == WD_STATE_IDLE then
> it just returned without doing anything, but now we fall through to the
> falling: label below.

I don't believe we do.  But I think the proposed logic does make this
difficult to detect.

Ira

> 
> So this patch seems like it introduces a bug, but actually it might just
> have a dead code problem.
> 
> regards,
> dan carpenter
> 
> > +
> > +falling:
> > +	/* wake/detect falling */
> > +	if (arche_pdata->wake_detect_state == WD_STATE_IDLE) {
> > +		arche_pdata->wake_detect_start = jiffies;
> >  		/*
> > -		 * If wake/detect line goes high after low, within less than
> > -		 * 30msec, then standby boot sequence is initiated, which is not
> > -		 * supported/implemented as of now. So ignore it.
> > +		 * In the beginning, when wake/detect goes low
> > +		 * (first time), we assume it is meant for coldboot
> > +		 * and set the flag. If wake/detect line stays low
> > +		 * beyond 30msec, then it is coldboot else fallback
> > +		 * to standby boot.
> >  		 */
> > -		if (arche_pdata->wake_detect_state == WD_STATE_BOOT_INIT) {
> > -			if (time_before(jiffies,
> > -					arche_pdata->wake_detect_start +
> > -					msecs_to_jiffies(WD_COLDBOOT_PULSE_WIDTH_MS))) {
> > -				arche_platform_set_wake_detect_state(arche_pdata,
> > -								     WD_STATE_IDLE);
> > -			} else {
> > -				/*
> > -				 * Check we are not in middle of irq thread
> > -				 * already
> > -				 */
> > -				if (arche_pdata->wake_detect_state !=
> > -						WD_STATE_COLDBOOT_START) {
> > -					arche_platform_set_wake_detect_state(arche_pdata,
> > -									     WD_STATE_COLDBOOT_TRIG);
> > -					rc = IRQ_WAKE_THREAD;
> > -				}
> > -			}
> > -		}
> > -	} else {
> > -		/* wake/detect falling */
> > -		if (arche_pdata->wake_detect_state == WD_STATE_IDLE) {
> > -			arche_pdata->wake_detect_start = jiffies;
> > -			/*
> > -			 * In the beginning, when wake/detect goes low
> > -			 * (first time), we assume it is meant for coldboot
> > -			 * and set the flag. If wake/detect line stays low
> > -			 * beyond 30msec, then it is coldboot else fallback
> > -			 * to standby boot.
> > -			 */
> > -			arche_platform_set_wake_detect_state(arche_pdata,
> > -							     WD_STATE_BOOT_INIT);
> > -		}
> > +		arche_platform_set_wake_detect_state(arche_pdata,
> > +						     WD_STATE_BOOT_INIT);
> >  	}
> >  
> > +out:
> >  	spin_unlock_irqrestore(&arche_pdata->wake_lock, flags);
> >  
> >  	return rc;
> > -- 
> > 2.34.1
> > 
>