linux-kernel - Re: [PATCH 4/5] dmaengine: sprd: Add Spreadtrum DMA configuration

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Date:   Fri, 13 Apr 2018 13:44:04 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Eric Long <eric.long@...eadtrum.com>,
        Mark Brown <broonie@...nel.org>, dmaengine@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] dmaengine: sprd: Add Spreadtrum DMA configuration

On 13 April 2018 at 11:39, Vinod Koul <vinod.koul@...el.com> wrote:
> On Thu, Apr 12, 2018 at 07:30:01PM +0800, Baolin Wang wrote:
>
>> >> > what does block and transaction len refer to here
>> >>
>> >>  Our DMA has 3 transfer mode: transaction transfer, block transfer and
>> >> fragment transfer. One transaction transfer can contain several blocks
>> >> transfer, and each block can be set proper block step. One block can
>> >> contain several fragments transfer with proper fragment step. It can
>> >> generate interrupts when one transaction transfer or block transfer or
>> >> fragment transfer is completed if user set the interrupt type. So here
>> >> we should set the length for transaction transfer, block transfer and
>> >> fragment transfer.
>> >
>> > what are the max size these types support?
>>
>> These types max size definition:
>>
>> #define SPRD_DMA_FRG_LEN_MASK GENMASK(16, 0)
>>
>> #define SPRD_DMA_BLK_LEN_MASK GENMASK(16, 0)
>>
>> #define SPRD_DMA_TRSC_LEN_MASK GENMASK(27, 0)
>
> They are register defines. How many items or bytes do each type of txn
> support?

These macros are the max size definitions, for example one fragment
length can support to 0x1ffff bytes, one transaction transfer can
support to 0xfffffff.

-- 
Baolin.wang
Best Regards