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SubjectRe: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoid circular references
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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.

> ---
> 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,

Laurent Pinchart



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