Re: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoidcircular references

[Sylwester Nawrocki]

Hi Laurent,

(adding Mauro and LMML at Cc)

On 10/29/2013 11:28 PM, Laurent Pinchart wrote:
> Hi Sylwester,
>
> Thank you for the patch.
>
> On Tuesday 29 October 2013 20:51:04 Sylwester Nawrocki wrote:
> > The clock core code is going to be modified so clk_get() takes
> > reference on the clock provider module. Until the potential circular
> > reference issue is properly addressed, we pass NULL as as the first
> > argument to clk_register(), in order to disallow sub-devices taking
> > a reference on the ISP module back trough clk_get(). This should
> > prevent locking the modules in memory.
> >
> > Cc: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Sylwester Nawrocki<s.nawrocki@xxxxxxxxxxx>
> > Signed-off-by: Kyungmin Park<kyungmin.park@xxxxxxxxxxx>
>
> Acked-by: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> Do you plan to push this to mainline as part of this patch series ? I don't
> have pending patches for the omap3isp that would conflict with this patch, so
> that would be fine with me.

Thanks, yes I thought this patch might be merged together through the clk
tree, if Mike is willing to take it and we get yours and Mauro's Ack on it.

> > ---
> > This patch has been "compile tested" only.
> >
> > ---
> >   drivers/media/platform/omap3isp/isp.c |   22 ++++++++++++++++------
> >   drivers/media/platform/omap3isp/isp.h |    1 +
> >   2 files changed, 17 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/platform/omap3isp/isp.c
> > b/drivers/media/platform/omap3isp/isp.c index df3a0ec..286027a 100644
> > --- a/drivers/media/platform/omap3isp/isp.c
> > +++ b/drivers/media/platform/omap3isp/isp.c
> > @@ -290,9 +290,11 @@ static int isp_xclk_init(struct isp_device *isp)
> >   	struct clk_init_data init;
> >   	unsigned int i;
> >
> > +	for (i = 0; i<  ARRAY_SIZE(isp->xclks); ++i)
> > +		isp->xclks[i].clk = ERR_PTR(-EINVAL);
> > +
> >   	for (i = 0; i<  ARRAY_SIZE(isp->xclks); ++i) {
> >   		struct isp_xclk *xclk =&isp->xclks[i];
> > -		struct clk *clk;
> >
> >   		xclk->isp = isp;
> >   		xclk->id = i == 0 ? ISP_XCLK_A : ISP_XCLK_B;
> > @@ -305,10 +307,15 @@ static int isp_xclk_init(struct isp_device *isp)
> >   		init.num_parents = 1;
> >
> >   		xclk->hw.init =&init;
> > -
> > -		clk = devm_clk_register(isp->dev,&xclk->hw);
> > -		if (IS_ERR(clk))
> > -			return PTR_ERR(clk);
> > +		/*
> > +		 * The first argument is NULL in order to avoid circular
> > +		 * reference, as this driver takes reference on the
> > +		 * sensor subdevice modules and the sensors would take
> > +		 * reference on this module through clk_get().
> > +		 */
> > +		xclk->clk = clk_register(NULL,&xclk->hw);
> > +		if (IS_ERR(xclk->clk))
> > +			return PTR_ERR(xclk->clk);
> >
> >   		if (pdata->xclks[i].con_id == NULL&&
> >   		pdata->xclks[i].dev_id == NULL)
> > @@ -320,7 +327,7 @@ static int isp_xclk_init(struct isp_device *isp)
> >
> >   		xclk->lookup->con_id = pdata->xclks[i].con_id;
> >   		xclk->lookup->dev_id = pdata->xclks[i].dev_id;
> > -		xclk->lookup->clk = clk;
> > +		xclk->lookup->clk = xclk->clk;
> >
> >   		clkdev_add(xclk->lookup);
> >   	}
> > @@ -335,6 +342,9 @@ static void isp_xclk_cleanup(struct isp_device *isp)
> >   	for (i = 0; i<  ARRAY_SIZE(isp->xclks); ++i) {
> >   		struct isp_xclk *xclk =&isp->xclks[i];
> >
> > +		if (!IS_ERR(xclk->clk))
> > +			clk_unregister(xclk->clk);
> > +
> >   		if (xclk->lookup)
> >   			clkdev_drop(xclk->lookup);
> >   	}
> > diff --git a/drivers/media/platform/omap3isp/isp.h
> > b/drivers/media/platform/omap3isp/isp.h index cd3eff4..1498f2b 100644
> > --- a/drivers/media/platform/omap3isp/isp.h
> > +++ b/drivers/media/platform/omap3isp/isp.h
> > @@ -135,6 +135,7 @@ struct isp_xclk {
> >   	struct isp_device *isp;
> >   	struct clk_hw hw;
> >   	struct clk_lookup *lookup;
> > +	struct clk *clk;
> >   	enum isp_xclk_id id;
> >
> >   	spinlock_t lock;	/* Protects enabled and divider */

--
Regards,
Sylwester
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