linux-kernel - Re: [PATCH v2 1/3] PM / clock_ops: Add pm_clk_add

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Date:	Wed, 22 Oct 2014 13:14:09 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	ssantosh@...nel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	khilman@...aro.org, Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-pm@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	grant.likely@...retlab.ca, ulf.hansson@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] PM / clock_ops: Add pm_clk_add_clk()

On Wed, Oct 22, 2014 at 10:02:41PM +0300, Grygorii Strashko wrote:
> On 10/22/2014 08:38 PM, Dmitry Torokhov wrote:
> >On Mon, Oct 20, 2014 at 03:56:02PM +0300, Grygorii Strashko wrote:
> >>From: Geert Uytterhoeven <geert+renesas@...der.be>
> >>
> >>The existing pm_clk_add() allows to pass a clock by con_id. However,
> >>when referring to a specific clock from DT, no con_id is available.
> >>
> >>Add pm_clk_add_clk(), which allows to specify the struct clk * directly.
> >>
> >>Reviewed-by: Kevin Hilman <khilman@...aro.org>
> >>Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >>Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> >>---
> >>
> >>  Pay attantion pls, that there is another series of patches
> >>  which have been posted already and which depends from this patch
> >>    "[PATCH v4 0/3] ARM: rk3288 : Add PM Domain support"
> >>    https://lkml.org/lkml/2014/10/20/105
> >>
> >>  drivers/base/power/clock_ops.c | 41 +++++++++++++++++++++++++++++++----------
> >>  include/linux/pm_clock.h       |  8 ++++++++
> >>  2 files changed, 39 insertions(+), 10 deletions(-)
> >>
> >>diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
> >>index 7836930..f14b767 100644
> >>--- a/drivers/base/power/clock_ops.c
> >>+++ b/drivers/base/power/clock_ops.c
> >>@@ -53,7 +53,8 @@ static inline int __pm_clk_enable(struct device *dev, struct clk *clk)
> >>   */
> >>  static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
> >>  {
> >>-	ce->clk = clk_get(dev, ce->con_id);
> >>+	if (!ce->clk)
> >>+		ce->clk = clk_get(dev, ce->con_id);
> >>  	if (IS_ERR(ce->clk)) {
> >>  		ce->status = PCE_STATUS_ERROR;
> >>  	} else {
> >>@@ -63,15 +64,8 @@ static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
> >>  	}
> >>  }
> >>
> >>-/**
> >>- * pm_clk_add - Start using a device clock for power management.
> >>- * @dev: Device whose clock is going to be used for power management.
> >>- * @con_id: Connection ID of the clock.
> >>- *
> >>- * Add the clock represented by @con_id to the list of clocks used for
> >>- * the power management of @dev.
> >>- */
> >>-int pm_clk_add(struct device *dev, const char *con_id)
> >>+static int __pm_clk_add(struct device *dev, const char *con_id,
> >>+			struct clk *clk)
> >>  {
> >>  	struct pm_subsys_data *psd = dev_to_psd(dev);
> >>  	struct pm_clock_entry *ce;
> >>@@ -93,6 +87,8 @@ int pm_clk_add(struct device *dev, const char *con_id)
> >>  			kfree(ce);
> >>  			return -ENOMEM;
> >>  		}
> >>+	} else {
> >>+		ce->clk = clk;
> >>  	}
> >>
> >>  	pm_clk_acquire(dev, ce);
> >>@@ -104,6 +100,31 @@ int pm_clk_add(struct device *dev, const char *con_id)
> >>  }
> >>
> >>  /**
> >>+ * pm_clk_add - Start using a device clock for power management.
> >>+ * @dev: Device whose clock is going to be used for power management.
> >>+ * @con_id: Connection ID of the clock.
> >>+ *
> >>+ * Add the clock represented by @con_id to the list of clocks used for
> >>+ * the power management of @dev.
> >>+ */
> >>+int pm_clk_add(struct device *dev, const char *con_id)
> >>+{
> >>+	return __pm_clk_add(dev, con_id, NULL);
> >
> >Bikeshedding: why do we need __pm_clk_add() and not simply have
> >"canonical" pm_clk_add_clk() and then do:
> >
> >int pm_clk_add(struct device *dev, const char *con_id)
> >{
> >	struct clk *clk;
> >
> >	clk = clk_get(dev, con_id);
> >	...
> >	return pm_clk_add_clk(dev, clk);
> >}
> 
> Hm. I did fast look at code and:
> 1) agree - there is a lot of thing which can be optimized ;)
> 2) in my strong opinion, this patch is the fastest and simplest
> way to introduce new API (take a look on pm_clock_entry->con_id
> management code) and It is exactly what we need as of now.

Yeah, I guess. We are lucky we do not crash when we are tryign to print
NULL strings (see pm_clk_acquire).

BTW, what is the point of doing pm_clk_add(dev, NULL)? We add clock
entry with status PCE_STATUS_ERROR and then have to handle it
everywhere? Can we just return -EINVAL if someone triies to pass NULL
ass con_id?

Thanks.

-- 
Dmitry
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