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Date: Thu, 23 Jan 2014 11:52:03 +0000
From: Russell King - ARM Linux <linux@....linux.org.uk>
To: Lothar Waßmann <LW@...O-electronics.de>
Cc: Sascha Hauer <s.hauer@...gutronix.de>,
Mark Rutland <mark.rutland@....com>, linux-pwm@...r.kernel.org,
Rob Landley <rob@...dley.net>, Pawel Moll <pawel.moll@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
Thierry Reding <thierry.reding@...il.com>,
Sascha Hauer <kernel@...gutronix.de>,
Kumar Gala <galak@...eaurora.org>,
Shawn Guo <shawn.guo@...aro.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2 2/2] pwm: imx: support polarity inversion
On Thu, Jan 23, 2014 at 08:37:14AM +0100, Lothar Waßmann wrote:
> This wouldn't buy much without a material change to of_pwm_get().
> The function of_parse_phandle_with_args() called by of_pwm_get()
> requires the number of args in the pwms property be greater or equal to
> the #pwm-cells property in the pwm node. Thus, the interesting case of
> having #pwm-cells = <3> without changing the existing users is
> prohibited by of_parse_phandle_with_args().
I really don't think that's a problem we need to be concerned with at
the moment. What we need is for the kernel to be able to parse files
with #pwm-cells = <2> with the pwms property containing two arguments,
and when they're updated to #pwm-cells = <3> with the pwms property
containing three arguments.
Yes, that means all the board dt files need to be updated at the same
time to include the additional argument, but I don't see that as a big
problem.
What we do need to do is to adjust the PWM parsing code such that it's
possible to use either specification without causing any side effects.
I would test this, but as u-boot is rather fscked at the moment and the
networking has broken on my cubox-i as a result... and it seems that the
u-boot developers have pissed off cubox-i u-boot hackers soo much that
they've dropped u-boot in favour of barebox...
drivers/pwm/core.c | 59 +++++++++++++++++++++++++++++------------------------
include/linux/pwm.h | 2 ++
2 files changed, 34 insertions(+), 27 deletions(-)
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 2ca95042a0b9..40adbce8ef0c 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -132,14 +132,11 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
}
struct pwm_device *
-of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
+of_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
{
struct pwm_device *pwm;
- if (pc->of_pwm_n_cells < 3)
- return ERR_PTR(-EINVAL);
-
- if (args->args[0] >= pc->npwm)
+ if (args->args_count < 2)
return ERR_PTR(-EINVAL);
pwm = pwm_request_from_chip(pc, args->args[0], NULL);
@@ -148,33 +145,45 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
pwm_set_period(pwm, args->args[1]);
- if (args->args[2] & PWM_POLARITY_INVERTED)
- pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
- else
- pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
+ if (args->args_count > 2) {
+ int err;
+
+ if (args->args[2] & PWM_POLARITY_INVERTED)
+ err = pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
+ else
+ err = pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
+
+ pwm_put(pwm);
+ return ERR_PTR(err);
+ }
return pwm;
}
+EXPORT_SYMBOL(of_pwm_xlate);
+
+struct pwm_device *
+of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
+{
+ if (pc->of_pwm_n_cells < 3)
+ return ERR_PTR(-EINVAL);
+
+ if (args->args_count != pc->of_pwm_n_cells)
+ return ERR_PTR(-EINVAL);
+
+ return of_pwm_xlate(pc, args);
+}
EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
static struct pwm_device *
of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
{
- struct pwm_device *pwm;
-
if (pc->of_pwm_n_cells < 2)
return ERR_PTR(-EINVAL);
- if (args->args[0] >= pc->npwm)
+ if (args->args_count != pc->of_pwm_n_cells)
return ERR_PTR(-EINVAL);
- pwm = pwm_request_from_chip(pc, args->args[0], NULL);
- if (IS_ERR(pwm))
- return pwm;
-
- pwm_set_period(pwm, args->args[1]);
-
- return pwm;
+ return of_pwm_xlate(pc, args);
}
static void of_pwmchip_add(struct pwm_chip *chip)
@@ -536,16 +545,12 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
goto put;
}
- if (args.args_count != pc->of_pwm_n_cells) {
- pr_debug("%s: wrong #pwm-cells for %s\n", np->full_name,
- args.np->full_name);
- pwm = ERR_PTR(-EINVAL);
- goto put;
- }
-
pwm = pc->of_xlate(pc, &args);
- if (IS_ERR(pwm))
+ if (IS_ERR(pwm)) {
+ pr_debug("%s: of_xlate failed for %s: %d\n", np->full_name,
+ args.np->full_name, (int)PTR_ERR(pwm));
goto put;
+ }
/*
* If a consumer name was not given, try to look it up from the
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index f0feafd184a0..14a823f77c31 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -188,6 +188,8 @@ struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
unsigned int index,
const char *label);
+struct pwm_device *of_pwm_xlate(struct pwm_chip *pc,
+ const struct of_phandle_args *args);
struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
const struct of_phandle_args *args);
--
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in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".
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