linux-kernel - Re: [PATCH v2 2/2] dmaengine: sprd: Add Spreadtrum DMA configuration

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Message-ID: <CAMz4kuKP2+SGoAqQPkt2sFuh3DZiO=7tQ=KHrbPUwQBqn-Mkgw@mail.gmail.com>
Date:   Fri, 11 May 2018 20:20:24 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Vinod Koul <vinod.koul@...aro.org>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Long <eric.long@...eadtrum.com>,
        Mark Brown <broonie@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        dmaengine@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] dmaengine: sprd: Add Spreadtrum DMA configuration

On 11 May 2018 at 20:04, Vinod Koul <vinod.koul@...aro.org> wrote:
> On 11-05-18, 19:58, Baolin Wang wrote:
>> On 11 May 2018 at 19:53, Vinod Koul <vkoul@...nel.org> wrote:
>> >> >
>> >> >> +/*
>> >> >> + * struct sprd_dma_config - DMA configuration structure
>> >> >> + * @cfg: dma slave channel runtime config
>> >> >> + * @src_addr: the source physical address
>> >> >> + * @dst_addr: the destination physical address
>> >> >> + * @block_len: specify one block transfer length
>> >> >> + * @transcation_len: specify one transcation transfer length
>> >> >> + * @src_step: source transfer step
>> >> >> + * @dst_step: destination transfer step
>> >> >> + * @wrap_ptr: wrap pointer address, once the transfer address reaches the
>> >> >> + * 'wrap_ptr', the next transfer address will jump to the 'wrap_to' address.
>> >> >> + * @wrap_to: wrap jump to address
>> >> >> + * @req_mode: specify the DMA request mode
>> >> >> + * @int_mode: specify the DMA interrupt type
>> >> >> + */
>> >> >> +struct sprd_dma_config {
>> >> >> +     struct dma_slave_config cfg;
>> >> >> +     phys_addr_t src_addr;
>> >> >> +     phys_addr_t dst_addr;
>> >> >
>> >> > these are already in cfg so why duplicate, same for few more here.
>> >>
>> >> We save them in 'struct sprd_dma_config' as one parameter for
>> >> sprd_dma_config(), otherwise we need add 2 more parameters (src and
>> >> dst) for sprd_dma_config().
>> >
>> > I am not sure I follow...
>> >
>> > I meant you can use sprd_dma_config.cfg->src_addr/dst_addr and remove src_addr &
>> > dst_addr in the sprd_dma_config. It duplicate..
>>
>> But we can not set values if dir == DMA_MEM_TO_DEV, since they
>> represent the device address, right?
>> sprd_dma_config.cfg->src_addr = sg_dma_address(sg);
>
> Ah right and that is another issue to fix then :) we should not store addresses
> you get for prep_ calls. They are supposed to be stored in the descriptor.
> Current approach is not correct.

OK. But we do not want to touch the descriptor structure, so we plan
to add 2 more parameters for sprd_dma_config().
And remove these 2 values from struct sprd_dma_config.

>
> You can get different prepare calls  (i think fixing this will remove 1 sg
> limitation).. and use the argument values and store in respective descriptors.
> Pls do see the other driver examples..
>
> --
> ~Vinod



-- 
Baolin.wang
Best Regards