From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Cousson, Benoit" <b-cousson@ti.com>
Subject: Re: [PATCH 04/11] OMAP3: DMA: HWMOD: Add hwmod data structures
Date: Wed, 04 Aug 2010 12:08:17 +0200
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To: "G, Manjunath Kondaiah" <manjugk@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>, "linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>, Paul Walmsley <paul@pwsan.com>, Tony Lindgren <tony@atomide.com>, "Sawant, Anand" <sawant@ti.com>, "Shilimkar, Santosh" <santosh.shilimkar@ti.com>, "Nayak, Rajendra" <rnayak@ti.com>, "Basak, Partha" <p-basak2@ti.com>, "Varadarajan, Charulatha" <charu@ti.com>

On 8/4/2010 2:35 AM, G, Manjunath Kondaiah wrote:
> Kevin,
>
>> From: Kevin Hilman [mailto:khilman@deeprootsystems.com]
>> Sent: Wednesday, August 04, 2010 3:27 AM
>>
>> Manjunatha GK<manjugk@ti.com>  writes:
>>
>>> This patch adds OMAP3 DMA hwmod structures.
>>>
>>> Signed-off-by: Manjunatha GK<manjugk@ti.com>
>>
>> [...]
>>
>>> +static struct omap_hwmod omap3xxx_dma_system_hwmod = {
>>> +	.name		= "dma",
>>> +	.class		=&omap3xxx_dma_hwmod_class,
>>> +	.mpu_irqs	= omap3xxx_dma_system_irqs,
>>> +	.mpu_irqs_cnt	= ARRAY_SIZE(omap3xxx_dma_system_irqs),
>>> +	.main_clk	= "l3_div_ck",
>>> +	.prcm = {
>>> +		.omap2 = {
>>> +			/* .clkctrl_reg = NULL, */
>>> +		},
>>> +	},
>>
>> Has this been tested?  Without valid fields here the hwmod
>> will never be
>> enabled.
>
> This patch series has been tested on both omap3 and omap4. I didn't find
> any entries for DMA module in prcm-common.h(for assigning .module_bit etc)
> hence I commented this for clarification.

There is no explicit PRCM control for the SDMA. You can just access the 
standby status and change the sysconfig idle and standby settings.
It uses the L3 interface clock as functional clock.
You should still use HWMOD_NO_IDLEST status to prevent the enable to crash.

In your case, I think that you are probably never explicitly enabling or 
disabling the dma device due to the library kind of API and the fact 
that the HW is managing is automatically, isn't it?

We had the same kind of discussion for the hwspinlock. Since these IPs 
are using interface clock as a functional clock, there is no need to 
explicitly enable them. But we should, otherwise we have no way to track 
the usage of this IP and potentially to enable the power domain that 
contains these IP.

Each time a dma channel is requested, you should call the 
pm_runtime_get, and pm_runtime_put() when the channel is not needed anymore.

Regards,
Benoit