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Re: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoid circula

To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Subject: Re: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoid circular references
From: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Date: Wed, 30 Oct 2013 00:57:52 +0100
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>, linux-arm-kernel@lists.infradead.org, mturquette@linaro.org, linux@arm.linux.org.uk, jiada_wang@mentor.com, kyungmin.park@samsung.com, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, LMML <linux-media@vger.kernel.org>, Mauro Carvalho Chehab <m.chehab@samsung.com>
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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@ideasonboard.com>
Signed-off-by: Sylwester Nawrocki<s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park<kyungmin.park@samsung.com>

Acked-by: Laurent Pinchart<laurent.pinchart@ideasonboard.com>

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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