linux-kernel - Re: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoid circular references

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Date:	Wed, 30 Oct 2013 00:57:52 +0100
From:	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, mturquette@...aro.org,
	linux@....linux.org.uk, jiada_wang@...tor.com,
	kyungmin.park@...sung.com, linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org, linux-mips@...ux-mips.org,
	linux-sh@...r.kernel.org, LMML <linux-media@...r.kernel.org>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>
Subject: Re: [PATCH v7 1/5] omap3isp: Modify clocks registration to avoid
 circular references

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@...asonboard.com>
>> Signed-off-by: Sylwester Nawrocki<s.nawrocki@...sung.com>
>> Signed-off-by: Kyungmin Park<kyungmin.park@...sung.com>
>
> Acked-by: Laurent Pinchart<laurent.pinchart@...asonboard.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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