linux-kernel - Re: [PATCH v3 RESEND 02/11] pwm: imx: remove ipg clock

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Message-ID: <20161228230116.4bf078ce@jawa>
Date:   Wed, 28 Dec 2016 23:01:16 +0100
From:   Lukasz Majewski <l.majewski@...ess.pl>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-pwm@...r.kernel.org,
        Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>,
        linux-kernel@...r.kernel.org,
        Fabio Estevam <fabio.estevam@....com>,
        Fabio Estevam <festevam@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Lothar Wassmann <LW@...o-electronics.de>,
        kernel@...gutronix.de, Philipp Zabel <p.zabel@...gutronix.de>
Subject: Re: [PATCH v3 RESEND 02/11] pwm: imx: remove ipg clock

Hi Stefan,

> Hi Stefan,
> 
> > On 2016-12-26 23:55, Lukasz Majewski wrote:
> > > From: Sascha Hauer <s.hauer@...gutronix.de>
> > > 
> > > The use of the ipg clock was introduced with commit 7b27c160c681
> > > ("pwm: i.MX: fix clock lookup").
> > > In the commit message it was claimed that the ipg clock is enabled
> > > for register accesses. This is true for the ->config() callback,
> > > but not for the ->set_enable() callback. Given that the ipg clock
> > > is not consistently enabled for all register accesses we can
> > > assume that either it is not required at all or that the current
> > > code does not work. Remove the ipg clock code for now so that
> > > it's no longer in the way of refactoring the driver.
> > 
> > Hi Lukasz,
> > 
> > Has my concern addressed in any way with this resend?
> > https://lkml.org/lkml/2016/11/22/729
> 
> Unfortunately not, since I don't have iMX7 for testing.
> 
> > 
> > Breaking hardware is usually not an option :-)
> 
> Yes, I know, but
> 
> Please look on the patch set from my perspective:
> 
> I originally wanted to add polarity inversion to PWM. Then, there was
> the request from you and Boris to go with "atomicity" support, so I
> converted the driver to support it.
> 
> This patch set has been resent on purpose at the end of merge window,
> so we do have some time to fix it if it would be accepted to -next
> tree (or any other PWM related one). Moreover, the burden for
> preparing patches would be smaller - since we all have agreed that
> "atomicity" is a more than welcome feature.
> 
> 
> > 
> > I checked the i.MX 7 reference manual again, and in this case the
> > peripheral access clock is a clock line named "ipg_clk_s" (Table
> > 12-20), with a clock root "PWM1_CLK_ROOT" (Table 5-12). In i.MX 7
> > all clocks are behind a single gate, so in fact it does not matter
> > which clock we take. Given that others have peripheral access
> > behind the "pwm" gate, I guess we should take the "pwm" gate...
> 
> 
> If possible please prepare a patch. It would be the best solution.

If I might ask - are you willing to prepare patch to fix iMX7 or shall
I roll back to the ipg code already present in main line ?


Best regards,
Łukasz Majewski

> 
> Thanks in advance,
> Łukasz Majewski
> 
> > 
> > --
> > Stefan
> > 
> > > 
> > > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > > Cc: Philipp Zabel <p.zabel@...gutronix.de>
> > > ---
> > > [commit message text refactored by Lukasz Majewski
> > > <l.majewski@...ess.pl>] ---
> > > Changes for v3:
> > > - New patch
> > > ---
> > >  drivers/pwm/pwm-imx.c | 19 +------------------
> > >  1 file changed, 1 insertion(+), 18 deletions(-)
> > > 
> > > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> > > index d600fd5..70609ef2 100644
> > > --- a/drivers/pwm/pwm-imx.c
> > > +++ b/drivers/pwm/pwm-imx.c
> > > @@ -49,7 +49,6 @@
> > >  
> > >  struct imx_chip {
> > >  	struct clk	*clk_per;
> > > -	struct clk	*clk_ipg;
> > >  
> > >  	void __iomem	*mmio_base;
> > >  
> > > @@ -204,17 +203,8 @@ static int imx_pwm_config(struct pwm_chip
> > > *chip, struct pwm_device *pwm, int duty_ns, int period_ns)
> > >  {
> > >  	struct imx_chip *imx = to_imx_chip(chip);
> > > -	int ret;
> > > -
> > > -	ret = clk_prepare_enable(imx->clk_ipg);
> > > -	if (ret)
> > > -		return ret;
> > >  
> > > -	ret = imx->config(chip, pwm, duty_ns, period_ns);
> > > -
> > > -	clk_disable_unprepare(imx->clk_ipg);
> > > -
> > > -	return ret;
> > > +	return imx->config(chip, pwm, duty_ns, period_ns);
> > >  }
> > >  
> > >  static int imx_pwm_enable(struct pwm_chip *chip, struct
> > > pwm_device *pwm) @@ -293,13 +283,6 @@ static int
> > > imx_pwm_probe(struct platform_device *pdev) return
> > > PTR_ERR(imx->clk_per); }
> > >  
> > > -	imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
> > > -	if (IS_ERR(imx->clk_ipg)) {
> > > -		dev_err(&pdev->dev, "getting ipg clock failed
> > > with %ld\n",
> > > -				PTR_ERR(imx->clk_ipg));
> > > -		return PTR_ERR(imx->clk_ipg);
> > > -	}
> > > -
> > >  	imx->chip.ops = &imx_pwm_ops;
> > >  	imx->chip.dev = &pdev->dev;
> > >  	imx->chip.base = -1;
> 

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