linux-kernel - Re: [PATCH] pwm: pwm-omap-dmtimer: fix probing problems by returning EPROBE

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Date:   Sun, 29 Jul 2018 20:08:04 +0200
From:   Ladislav Michl <ladis@...ux-mips.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Andreas Kemnade <andreas@...nade.info>,
        David Rivshin <drivshin@...worx.com>,
        linux-pwm@...r.kernel.org, linux-omap <linux-omap@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>, Keerthy <j-keerthy@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH] pwm: pwm-omap-dmtimer: fix probing problems by returning
 EPROBE_DEFER

On Sun, Jul 29, 2018 at 08:32:41AM +0200, H. Nikolaus Schaller wrote:
> Hi,
> 
> > Am 28.07.2018 um 22:35 schrieb Ladislav Michl <ladis@...ux-mips.org>:
> > 
> > Hi Andreas,
> > 
> > On Sat, Jul 28, 2018 at 06:59:14PM +0200, Andreas Kemnade wrote:
> >> I got this in the kernel log:
> >> [    0.756042] omap-dmtimer-pwm dmtimer-pwm: dmtimer pdata structure NULL
> >> [    0.756134] omap-dmtimer-pwm: probe of dmtimer-pwm failed with error -22
> >> 
> >> the probe function has to wait until omap_dm_timer_probe() in
> >> clocksource/timer-ti-dm.c has initialized pdata, so defer probing
> > 
> > There already is a patch by David Rivshin addressing the same issue...
> 
> Here it is:
> 
> https://patchwork.ozlabs.org/patch/943148/
> 
> but hasn't arrived in linux-next.

That's because there'll be v3.

> But it is questionable if a driver should dev_info() about doing deferred probing.
> IMHO, it should just do it which is how Andreas' patch works.

See here: https://patchwork.ozlabs.org/patch/949659/

> >> Fixes: b7290cf6ff78 (pwm: pwm-omap-dmtimer: Adapt driver to utilize dmtimer pdata ops)
> >> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> >> ---
> >> drivers/pwm/pwm-omap-dmtimer.c | 3 +--
> >> 1 file changed, 1 insertion(+), 2 deletions(-)
> >> 
> >> diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
> >> index 665da3c8fbce..808835179c2e 100644
> >> --- a/drivers/pwm/pwm-omap-dmtimer.c
> >> +++ b/drivers/pwm/pwm-omap-dmtimer.c
> >> @@ -264,8 +264,7 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
> >> 
> >> 	timer_pdata = dev_get_platdata(&timer_pdev->dev);
> >> 	if (!timer_pdata) {
> >> -		dev_err(&pdev->dev, "dmtimer pdata structure NULL\n");
> >> -		ret = -EINVAL;
> >> +		ret = -EPROBE_DEFER;
> >> 		goto put;
> >> 	}
> >> 
> >> -- 
> >> 2.11.0
> >> 
> 
> BR,
> Nikolaus
>