Re: [PATCH] ARM: SAMSUNG: dma: Remove unnecessary code

[Padma Venkat <padma.kvr@gmail.com>]

Hi Arnd,

On Mon, Feb 4, 2013 at 11:13 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Monday 04 February 2013, Padmavathi Venna wrote:
>> diff --git a/arch/arm/plat-samsung/dma-ops.c b/arch/arm/plat-samsung/dma-ops.c
>> index 71d58dd..ec0d731 100644
>> --- a/arch/arm/plat-samsung/dma-ops.c
>> +++ b/arch/arm/plat-samsung/dma-ops.c
>> @@ -23,23 +23,15 @@ static unsigned samsung_dmadev_request(enum dma_ch dma_ch,
>>                               struct device *dev, char *ch_name)
>>  {
>>       dma_cap_mask_t mask;
>> -     void *filter_param;
>>
>>       dma_cap_zero(mask);
>>       dma_cap_set(param->cap, mask);
>>
>> -     /*
>> -      * If a dma channel property of a device node from device tree is
>> -      * specified, use that as the fliter parameter.
>> -      */
>> -     filter_param = (dma_ch == DMACH_DT_PROP) ?
>> -             (void *)param->dt_dmach_prop : (void *)dma_ch;
>> -
>>       if (dev->of_node)
>>               return (unsigned)dma_request_slave_channel(dev, ch_name);
>>       else
>>               return (unsigned)dma_request_channel(mask, pl330_filter,
>> -                                                     filter_param);
>> +                                                     (void *)dma_ch);
>>  }
>
> This still looks wrong to me, because the pl330_filter function now tkes
> a struct dma_pl330_filter_args pointer argument, not dma_ch name.

Below is my understanding about generic dma and our discussion on
previous versions of my patches.

I can’t pass single dma channel number(may be not dma_ch name in your
comment above) as void* argument to pl330_filter.  Because I also need
to compare against the dma controller device node, as my requested
channel can belong to any of the available dma controller on SoC.  So
I either need to pass pointer to dma_spec as void* argument which
holds the dma controller node and required channel number or I can
pass pointer to dma_pl330_filter_args as per your dw_dmac patches.

If I pass pointer to dma_spec I can have a check like below in my
filter function
return ((chan->private == dma_spec->np) && (chan->chan_id == dma_spec->args[0]))

Or if I pass dma_pl330_filter_args I can have a check like below.
return ((chan->device == &fargs->pdmac->ddma) && (chan->chan_id ==
fargs->chan_id));

I modified  the pl330_filter function based on your dw_dmac patches.
Indeed I don’t need to pass pointer to pdmac object as 3rd arg in
of_dma_controller_register .  Even I pass NULL here works for me.
Can I pass NULL here as the third argument in of_dma_controller_register?
Please clarify me which is best way of doing this and correct me if my
understanding is wrong.

>
>         Arnd
Thanks
Padma