Re: [PATCH] pwm: atmel-hlcdc: Fix default PWM polarity

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Tue, 17 May 2016 14:19:17 +0200
Thierry Reding <thierry.reding@gmail.com> wrote:

> On Tue, May 17, 2016 at 02:08:03PM +0200, Boris Brezillon wrote:
> > Hi Thierry,
> > 
> > On Tue, 17 May 2016 13:00:05 +0200
> > Thierry Reding <thierry.reding@gmail.com> wrote:
> >   
> > > On Tue, May 17, 2016 at 11:12:32AM +0200, Boris Brezillon wrote:  
> > > > The PWM device exposed by the HLCDC IP is configured with an inverted
> > > > polarity by default. Registering the PWM chip with the normal polarity
> > > > was not a problem before commit 42e8992c58d4 ("pwm: Add core
> > > > infrastructure to allow atomic updates") because the ->set_polarity()
> > > > hook was called no matter the current polarity state, but this is no longer
> > > > the case.
> > > > 
> > > > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > > > Fixes: 42e8992c58d4 ("pwm: Add core infrastructure to allow atomic updates")    
> > > 
> > > That's not technically correct, because it's the driver that has the
> > > bug. The core change merely exposes it. How about if I sort this into
> > > the pwm-atomic branch and reword the commit message accordingly? That
> > > way things should all stay bisectible.
> > > 
> > > Then again, given the breakage caused by the pwm_args patch I suppose
> > > it doesn't matter much because that's part of a stable branch that I
> > > can't rebase.  
> > 
> > If I understood correctly, you plan to rebase your pwm-atomic branch to
> > insert this commit before commit 42e8992c58d4 ("pwm: Add core
> > infrastructure to allow atomic updates").
> > 
> > Could you consider taking the following commit (or something similar if
> > you already have a fix) as the first commit of your pwm-atomic branch?
> > 
> > Sorry for the mess around the introduction of pwm_args and pwm_state
> > (that's not an excuse, but I've reworked this series so many time that I
> > forgot to check bisectibility on the last versions :-().
> > 
> > ---
> > From ad73fa3a56c7320979425d64ab54c09b9d83d4cf Mon Sep 17 00:00:00 2001
> > From: Boris Brezillon <boris.brezillon@free-electrons.com>
> > Date: Tue, 17 May 2016 13:55:02 +0200
> > Subject: [PATCH] pwm: Fix pwm_apply_args() call sites
> > 
> > pwm_apply_args() is supposed to initialize a PWM device according to the
> > arguments provided by the DT or the PWM lookup, but this function was
> > called inside pwm_device_request(), which in turn was called before the
> > core had a chance to initialize the pwm->args fields.
> > 
> > Fix that by calling pwm_apply_args directly in pwm_get() and of_pwm_get()
> > after initializing pwm->args field.
> > 
> > This commit also fixes an invalid pointer dereference introduced by
> > commit e39c0df1be5a ("pwm: Introduce the pwm_args concept").
> > 
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > Fixes: e39c0df1be5a ("pwm: Introduce the pwm_args concept")
> > ---
> >  drivers/pwm/core.c | 27 +++++++++++++++++----------
> >  1 file changed, 17 insertions(+), 10 deletions(-)  
> 
> This looks good to me. However I can't easily apply this because git
> gets confused by the existing headers. Also manually copying out the
> patch yields patch corruption that I don't exactly know how to fix.
> 
> I think you can inline patches by using a scissor mark (--- >8 ---)
> instead of the signature separator (---). Or you can attach the patch
> with "Content-Disposition: inline".

Ok, it's my PEBKAC day. Here it is with the scissor mark. As mentioned
on IRC, you'll also have to squash those changes [1] into 93c0d9b
("pwm: Keep PWM state in sync with hardware state").

> 
> Rather than putting this into the pwm-atomic branch, I'll probably stick
> it into the pwm-args branch on top of the existing patch. Technically
> only the existing patch needs to be stable, so the branch can still
> evolve.

Ok, great!

Thanks,

Boris

[1]http://code.bulix.org/egoo4y-98645

--->8---
From ad73fa3a56c7320979425d64ab54c09b9d83d4cf Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@free-electrons.com>
Date: Tue, 17 May 2016 13:55:02 +0200
Subject: [PATCH] pwm: Fix pwm_apply_args() call sites

pwm_apply_args() is supposed to initialize a PWM device according to the
arguments provided by the DT or the PWM lookup, but this function was
called inside pwm_device_request(), which in turn was called before the
core had a chance to initialize the pwm->args fields.

Fix that by calling pwm_apply_args directly in pwm_get() and of_pwm_get()
after initializing pwm->args field.

This commit also fixes an invalid pointer dereference introduced by
commit e39c0df1be5a ("pwm: Introduce the pwm_args concept").

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: e39c0df1be5a ("pwm: Introduce the pwm_args concept")
---
 drivers/pwm/core.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 680fbc7..22cf395 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -128,13 +128,6 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
 	set_bit(PWMF_REQUESTED, &pwm->flags);
 	pwm->label = label;
 
-	/*
-	 * FIXME: This should be removed once all PWM users properly make use
-	 * of struct pwm_args to initialize the PWM device. As long as this is
-	 * here, the PWM state and hardware state can get out of sync.
-	 */
-	pwm_apply_args(pwm);
-
 	return 0;
 }
 
@@ -627,6 +620,13 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
 
 	pwm->label = con_id;
 
+	/*
+	 * FIXME: This should be removed once all PWM users properly make use
+	 * of struct pwm_args to initialize the PWM device. As long as this is
+	 * here, the PWM state and hardware state can get out of sync.
+	 */
+	pwm_apply_args(pwm);
+
 put:
 	of_node_put(args.np);
 
@@ -754,13 +754,20 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
 	if (!chip)
 		goto out;
 
-	pwm->args.period = chosen->period;
-	pwm->args.polarity = chosen->polarity;
-
 	pwm = pwm_request_from_chip(chip, chosen->index, con_id ?: dev_id);
 	if (IS_ERR(pwm))
 		goto out;
 
+	pwm->args.period = chosen->period;
+	pwm->args.polarity = chosen->polarity;
+
+	/*
+	 * FIXME: This should be removed once all PWM users properly make use
+	 * of struct pwm_args to initialize the PWM device. As long as this is
+	 * here, the PWM state and hardware state can get out of sync.
+	 */
+	pwm_apply_args(pwm);
+
 out:
 	mutex_unlock(&pwm_lookup_lock);
 	return pwm;