Consider moving the init of pl330 to earlier?

Consider moving the init of pl330 to earlier?

[Ray Jui]

Hi,

How do you guys like the idea of moving the driver initialization of the 
pl330 DMA driver to earlier? For example, to arch_initcall_sync or 
subsys_initcall? Currently the pl330 driver is registered through 
module_amba_driver call, which translates to device_initcall in the end. 
This is a bit late considering in many systems, DMA controller is one of 
the core components that may have many slave devices depending on. Most 
slave drivers are typically done at device_initcall. When done at the 
same level, DMA may not be ready while the slave devices are being 
initialized. In addition, under the drivers/dma directory, we currently 
have various other DMA drivers also done at subsys_initcall.

One issue that I'm seeing with the Broadcom Cygnus SoC is that, when we 
try to use DMA with SPI (PL022), the request for DMA channel would fail 
because the spi-pl022 driver we use is initialized at subsys_initcall. 
At the time the PL330 driver is not yet initialized. The reason why 
spi-pl022 is done at subsys_initcall is that some regulators communicate 
through the SPI bus so people decided to move it to earlier (commit 
25c8e03b by Linus Walleij), which seems to be a valid reason to me.

Thanks,

Ray

Re: Consider moving the init of pl330 to earlier?

[Vinod Koul]

On Thu, Oct 09, 2014 at 02:35:11PM -0700, Ray Jui wrote:
> Hi,
> 
> How do you guys like the idea of moving the driver initialization of
> the pl330 DMA driver to earlier? For example, to arch_initcall_sync
> or subsys_initcall? Currently the pl330 driver is registered through
> module_amba_driver call, which translates to device_initcall in the
> end. This is a bit late considering in many systems, DMA controller
> is one of the core components that may have many slave devices
> depending on. Most slave drivers are typically done at
> device_initcall. When done at the same level, DMA may not be ready
> while the slave devices are being initialized. In addition, under
> the drivers/dma directory, we currently have various other DMA
> drivers also done at subsys_initcall.
> 
> One issue that I'm seeing with the Broadcom Cygnus SoC is that, when
> we try to use DMA with SPI (PL022), the request for DMA channel
> would fail because the spi-pl022 driver we use is initialized at
> subsys_initcall. At the time the PL330 driver is not yet
> initialized. The reason why spi-pl022 is done at subsys_initcall is
> that some regulators communicate through the SPI bus so people
> decided to move it to earlier (commit 25c8e03b by Linus Walleij),
> which seems to be a valid reason to me.
As a subsytem we encourage folks to use early init calls and then have
clients use late_init so that dependency is solved.

So feel free to send the patch

-- 
~Vinod

Re: Consider moving the init of pl330 to earlier?

[Ray Jui]

On 10/15/2014 11:59 PM, Vinod Koul wrote:
> On Thu, Oct 09, 2014 at 02:35:11PM -0700, Ray Jui wrote:
>> Hi,
>>
>> How do you guys like the idea of moving the driver initialization of
>> the pl330 DMA driver to earlier? For example, to arch_initcall_sync
>> or subsys_initcall? Currently the pl330 driver is registered through
>> module_amba_driver call, which translates to device_initcall in the
>> end. This is a bit late considering in many systems, DMA controller
>> is one of the core components that may have many slave devices
>> depending on. Most slave drivers are typically done at
>> device_initcall. When done at the same level, DMA may not be ready
>> while the slave devices are being initialized. In addition, under
>> the drivers/dma directory, we currently have various other DMA
>> drivers also done at subsys_initcall.
>>
>> One issue that I'm seeing with the Broadcom Cygnus SoC is that, when
>> we try to use DMA with SPI (PL022), the request for DMA channel
>> would fail because the spi-pl022 driver we use is initialized at
>> subsys_initcall. At the time the PL330 driver is not yet
>> initialized. The reason why spi-pl022 is done at subsys_initcall is
>> that some regulators communicate through the SPI bus so people
>> decided to move it to earlier (commit 25c8e03b by Linus Walleij),
>> which seems to be a valid reason to me.
> As a subsytem we encourage folks to use early init calls and then have
> clients use late_init so that dependency is solved.
>
> So feel free to send the patch
>
Will do. Thanks!

Ray