On Sun, 4 Jan 2015, Laurent Pinchart wrote:
> Hi Guennadi,
>
> Thank you for the patch.
>
> On Friday 02 January 2015 21:18:41 Guennadi Liakhovetski wrote:
> > From aeaee56e04d023f3a019d2595ef5128015acdb06 Mon Sep 17 00:00:00 2001
> > From: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > Date: Fri, 2 Jan 2015 12:26:41 +0100
> > Subject: [PATCH 2/2] V4L2: add CCF support to the v4l2_clk API
> >
> > V4L2 clocks, e.g. used by camera sensors for their master clock, do not
> > have to be supplied by a different V4L2 driver, they can also be
> > supplied by an independent source. In this case the standart kernel
> > clock API should be used to handle such clocks. This patch adds support
> > for such cases.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> >
> > Hi Laurent,
> > Thanks for the comment. The idea of allocating a new object for each "get"
> > operation seems a bit weird to me, and completely trusting the user is a
> > bit scary... :) But yes, it can work this way too, I think, and the user
> > can screw either way too, anyway.
>
> The user needs to get it right for when we'll replace v4l2_clk_get() with
> clk_get(), so I'd rather force it to get it right now.
>
> > So, here comes a v2. Something like this?
> >
> > v2: don't add CCF-related clocks on the global list, just allocate a new
> > instance on each v4l2_clk_get()
> >
> > drivers/media/v4l2-core/v4l2-clk.c | 45 +++++++++++++++++++++++++++++++---
> > include/media/v4l2-clk.h | 2 ++
> > 2 files changed, 44 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-clk.c
> > b/drivers/media/v4l2-core/v4l2-clk.c index c210906..f5d1688 100644
> > --- a/drivers/media/v4l2-core/v4l2-clk.c
> > +++ b/drivers/media/v4l2-core/v4l2-clk.c
> > @@ -9,6 +9,7 @@
> > */
> >
> > #include <linux/atomic.h>
> > +#include <linux/clk.h>
> > #include <linux/device.h>
> > #include <linux/errno.h>
> > #include <linux/list.h>
> > @@ -42,6 +43,18 @@ static struct v4l2_clk *v4l2_clk_find(const char *dev_id,
> > const char *id) struct v4l2_clk *v4l2_clk_get(struct device *dev, const
> > char *id) {
> > struct v4l2_clk *clk;
> > + struct clk *ccf_clk = clk_get(dev, id);
> > +
> > + if (!IS_ERR(ccf_clk)) {
> > + clk = kzalloc(sizeof(struct v4l2_clk), GFP_KERNEL);
> > + if (!clk) {
> > + clk_put(ccf_clk);
> > + return ERR_PTR(-ENOMEM);
> > + }
> > + clk->clk = ccf_clk;
> > +
> > + return clk;
> > + }
>
> If clk_get() returns -EPROBE_DEFER I think you should return the error code to
> the user instead of falling back to the v4l2 clocks.
This is the case, when a clock is correctly set up in DT, but no suitable
provider is registered yet, right? I think such a case isn't very likely,
but yes, can do, makes more sense, perhaps.
> > mutex_lock(&clk_lock);
> > clk = v4l2_clk_find(dev_name(dev), id);
> > @@ -61,6 +74,12 @@ void v4l2_clk_put(struct v4l2_clk *clk)
> > if (IS_ERR(clk))
> > return;
> >
> > + if (clk->clk) {
> > + clk_put(clk->clk);
> > + kfree(clk);
> > + return;
> > + }
> > +
> > mutex_lock(&clk_lock);
> >
> > list_for_each_entry(tmp, &clk_list, list)
> > @@ -98,8 +117,12 @@ static void v4l2_clk_unlock_driver(struct v4l2_clk *clk)
> >
> > int v4l2_clk_enable(struct v4l2_clk *clk)
> > {
> > - int ret = v4l2_clk_lock_driver(clk);
> > + int ret;
> >
> > + if (clk->clk)
> > + return clk_enable(clk->clk);
>
> Shouldn't you use clk_prepare_enable() ? CCF requires a prepare call before
> enabling the clock.
Right, my fault, thanks for pointing out.
> > +
> > + ret = v4l2_clk_lock_driver(clk);
> > if (ret < 0)
> > return ret;
> >
> > @@ -125,6 +148,9 @@ void v4l2_clk_disable(struct v4l2_clk *clk)
> > {
> > int enable;
> >
> > + if (clk->clk)
> > + return clk_disable(clk->clk);
>
> Likewise, clk_disable_unprepare() ?
Sure. Ok, these are trivial changes, perhaps we can wait for Josh's test
results, then I can submit a v3 with (hopefully) all required changes.
Thanks
Guennadi
> > +
> > mutex_lock(&clk->lock);
> >
> > enable = --clk->enable;
> > @@ -142,8 +168,12 @@ EXPORT_SYMBOL(v4l2_clk_disable);
> >
> > unsigned long v4l2_clk_get_rate(struct v4l2_clk *clk)
> > {
> > - int ret = v4l2_clk_lock_driver(clk);
> > + int ret;
> > +
> > + if (clk->clk)
> > + return clk_get_rate(clk->clk);
> >
> > + ret = v4l2_clk_lock_driver(clk);
> > if (ret < 0)
> > return ret;
> >
> > @@ -162,7 +192,16 @@ EXPORT_SYMBOL(v4l2_clk_get_rate);
> >
> > int v4l2_clk_set_rate(struct v4l2_clk *clk, unsigned long rate)
> > {
> > - int ret = v4l2_clk_lock_driver(clk);
> > + int ret;
> > +
> > + if (clk->clk) {
> > + long r = clk_round_rate(clk->clk, rate);
> > + if (r < 0)
> > + return r;
> > + return clk_set_rate(clk->clk, r);
> > + }
> > +
> > + ret = v4l2_clk_lock_driver(clk);
> >
> > if (ret < 0)
> > return ret;
> > diff --git a/include/media/v4l2-clk.h b/include/media/v4l2-clk.h
> > index 8f06967..4402b2d 100644
> > --- a/include/media/v4l2-clk.h
> > +++ b/include/media/v4l2-clk.h
> > @@ -22,6 +22,7 @@
> > struct module;
> > struct device;
> >
> > +struct clk;
> > struct v4l2_clk {
> > struct list_head list;
> > const struct v4l2_clk_ops *ops;
> > @@ -30,6 +31,7 @@ struct v4l2_clk {
> > int enable;
> > struct mutex lock; /* Protect the enable count */
> > atomic_t use_count;
> > + struct clk *clk;
> > void *priv;
> > };
>
> --
> Regards,
>
> Laurent Pinchart
>
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