linux-kernel - Re: [PATCH 2/2] dma: Add Spreadtrum DMA controller driver

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Date:   Tue, 25 Jul 2017 14:28:39 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 2/2] dma: Add Spreadtrum DMA controller driver

Hi,

On 25 July 2017 at 11:38, Vinod Koul <vinod.koul@...el.com> wrote:
> On Mon, Jul 24, 2017 at 02:46:00PM +0800, Baolin Wang wrote:
>> Hi,
>>
>> On 六,  7月 22, 2017 at 01:27:31下午 +0530, Vinod Koul wrote:
>> > On Tue, Jul 18, 2017 at 03:06:12PM +0800, Baolin Wang wrote:
>
>> > > +static void sprd_dma_set_uid(struct sprd_dma_chn *mchan)
>> > > +{
>> > > + struct sprd_dma_dev *sdev = to_sprd_dma_dev(&mchan->chan);
>> > > + u32 dev_id = mchan->dev_id;
>> > > +
>> > > + if (dev_id != DMA_SOFTWARE_UID)
>> >
>> > Whats a UID?
>>
>> It is for users, every user was assigned one unique hardware ID.
>> Then the user can trigger the DMA to transfer by the user ID.
>
> sounds like a slave id to me (hint read again struct dma_slave_config)

Yes.

>
>> > > + u32 fragmens_len;
>> > > + u32 block_len;
>> >
>> > oh please, I think I will stop here now :(
>> >
>> > > + u32 transcation_len;
>> > > + u32 src_step;
>> > > + u32 des_step;
>> > > + u32 src_frag_step;
>> > > + u32 dst_frag_step;
>> > > + u32 src_blk_step;
>> > > + u32 dst_blk_step;
>> > > + u32 wrap_ptr;
>> > > + u32 wrap_to;
>> > > + u32 dev_id;
>> > > + enum dma_end_type is_end;
>> >
>> > Looking at this I think these are overkill, many of them can be handled
>> > properly by current dmaengine interfaces, so please use those before you
>> > invent your own...
>> >
>> > Also the code is bloated because you don't use virt-dma, pls use that. I
>> > skipped many parts of the driver as I feel driver needs more work.
>>
>> OK. I will check the virt-dma. Thanks for your commnets.
>
> Ok, but the bigger concern is that people have defined generic interfaces
> for everyone to use, so you should also use them, the hw doesn't seem
> anything special which cannot be accommodated in the current fwk, if not do
> tell me which parts don't fit before you invent your own interfaces...

OK. I think I missed something and I will check the generic interfaces
again. Thanks for your help.

-- 
Baolin.wang
Best Regards