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Date: Thu, 17 May 2018 14:28:36 +0800
From: Baolin Wang <baolin.wang@...aro.org>
To: Vinod <vkoul@...nel.org>
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 v3 2/2] dmaengine: sprd: Add Spreadtrum DMA configuration
On 17 May 2018 at 14:11, Vinod <vkoul@...nel.org> wrote:
> On 17-05-18, 14:02, Baolin Wang wrote:
>> Hi Vinod,
>>
>> On 17 May 2018 at 13:14, Vinod <vkoul@...nel.org> wrote:
>> > On 11-05-18, 21:06, Baolin Wang wrote:
>> >> +struct sprd_dma_config {
>> >> + struct dma_slave_config cfg;
>> >> + u32 block_len;
>> >> + u32 transcation_len;
>> >
>> > /s/transcation/transaction
>>
>> OK.
>>
>> >
>> > now in code I see block_len and this filled by len which is sg_dma_len()?
>> > So why two varibales when you are using only one.
>>
>> Like I explained before, we have transaction transfer, block transfer
>> and fragment transfer, and we should set the length for each transfer.
>> In future, we we will use these two variables in cyclic mode, but for
>> prep_sg, we just make them equal to
>
> Please add them when you have use for it. Sorry linux kernel is not a place for
> dumping future use work
We now use them, since we have registers to configure, and we just set
the same values for them now.
>>
>> >
>> > Second, you are storing parameters programmed thru _prep call into
>> > _dma_config. That is not correct.
>> >
>> > We use these to store channel parameters and NOT transaction parameters which
>> > would differ with each txn. No wonder you can only support only 1 txn :)
>>
>> Fine, we can remove block_len/transcation_len from 'struct
>> sprd_dma_config'. Any other issues for the 'struct sprd_dma_config'?
>
> Yes see the comments on prep_
OK.
>>
>> >
>> > Lastly, if these are same values why not use src/dstn_max_burst?
>>
>> The fragment length will be filled by src/dstn_max_burst,so we can not
>> use it again.
>>
>> >
>> >> +static enum sprd_dma_datawidth
>> >> +sprd_dma_get_datawidth(enum dma_slave_buswidth buswidth)
>> >> +{
>> >> + switch (buswidth) {
>> >> + case DMA_SLAVE_BUSWIDTH_1_BYTE:
>> >> + case DMA_SLAVE_BUSWIDTH_2_BYTES:
>> >> + case DMA_SLAVE_BUSWIDTH_4_BYTES:
>> >> + case DMA_SLAVE_BUSWIDTH_8_BYTES:
>> >> + return ffs(buswidth) - 1;
>> >> + default:
>> >> + return SPRD_DMA_DATAWIDTH_4_BYTES;
>> >
>> > Does default make sense, should we error out?
>>
>> Not one error, maybe we can give some warning information.
>
> well client programmed a wrong value, so I expect this to error out.
OK.
>
>>
>> >
>> >> +static u32 sprd_dma_get_step(enum dma_slave_buswidth buswidth)
>> >> +{
>> >> + switch (buswidth) {
>> >> + case DMA_SLAVE_BUSWIDTH_1_BYTE:
>> >> + case DMA_SLAVE_BUSWIDTH_2_BYTES:
>> >> + case DMA_SLAVE_BUSWIDTH_4_BYTES:
>> >> + case DMA_SLAVE_BUSWIDTH_8_BYTES:
>> >> + return buswidth;
>> >> +
>> >> + default:
>> >> + return SPRD_DMA_DWORD_STEP;
>> >
>> > Does default make sense, should we error out?
>>
>> Ditto.
>>
>> >
>> >> +static int sprd_dma_config(struct dma_chan *chan, struct sprd_dma_desc *sdesc,
>> >> + dma_addr_t src, dma_addr_t dst,
>> >> + struct sprd_dma_config *slave_cfg)
>> >> +{
>> >> + struct sprd_dma_dev *sdev = to_sprd_dma_dev(chan);
>> >> + struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
>> >> + struct sprd_dma_chn_hw *hw = &sdesc->chn_hw;
>> >> + u32 fix_mode = 0, fix_en = 0, wrap_en = 0, wrap_mode = 0;
>> >> + u32 src_datawidth, dst_datawidth, temp;
>> >> +
>> >> + if (slave_cfg->cfg.slave_id)
>> >> + schan->dev_id = slave_cfg->cfg.slave_id;
>> >> +
>> >> + hw->cfg = SPRD_DMA_DONOT_WAIT_BDONE << SPRD_DMA_WAIT_BDONE_OFFSET;
>> >> +
>> >> + temp = slave_cfg->wrap_ptr & SPRD_DMA_LOW_ADDR_MASK;
>> >> + temp |= (src >> SPRD_DMA_HIGH_ADDR_OFFSET) & SPRD_DMA_HIGH_ADDR_MASK;
>> >> + hw->wrap_ptr = temp;
>> >> +
>> >> + temp = slave_cfg->wrap_to & SPRD_DMA_LOW_ADDR_MASK;
>> >> + temp |= (dst >> SPRD_DMA_HIGH_ADDR_OFFSET) & SPRD_DMA_HIGH_ADDR_MASK;
>> >> + hw->wrap_to = temp;
>> >> +
>> >> + hw->src_addr = src & SPRD_DMA_LOW_ADDR_MASK;
>> >> + hw->des_addr = dst & SPRD_DMA_LOW_ADDR_MASK;
>> >> +
>> >> + if ((slave_cfg->src_step != 0 && slave_cfg->dst_step != 0)
>> >> + || (slave_cfg->src_step | slave_cfg->dst_step) == 0) {
>> >
>> > this check doesnt seem right to me, what are you trying here?
>>
>> This is SPRD DMA internal feature: address-fix transfer. If the src
>> step and dst step both are 0 or both are not 0, that means we can not
>> enable the fix mode.
>> If one is 0 and another one is not, we can enable the fix mode.
>
> A comment here would help explain this :)
Sure.
>>
>> >
>> >> + fix_en = 0;
>> >> + } else {
>> >> + fix_en = 1;
>> >> + if (slave_cfg->src_step)
>> >> + fix_mode = 1;
>> >> + else
>> >> + fix_mode = 0;
>> >> + }
>> >> +
>> >> + if (slave_cfg->wrap_ptr && slave_cfg->wrap_to) {
>> >> + wrap_en = 1;
>> >> + if (slave_cfg->wrap_to == src) {
>> >> + wrap_mode = 0;
>> >> + } else if (slave_cfg->wrap_to == dst) {
>> >> + wrap_mode = 1;
>> >> + } else {
>> >> + dev_err(sdev->dma_dev.dev, "invalid wrap mode\n");
>> >> + return -EINVAL;
>> >> + }
>> >> + }
>> >> +
>> >> + hw->intc = slave_cfg->int_mode | SPRD_DMA_CFG_ERR_INT_EN;
>> >> +
>> >> + src_datawidth = sprd_dma_get_datawidth(slave_cfg->cfg.src_addr_width);
>> >> + dst_datawidth = sprd_dma_get_datawidth(slave_cfg->cfg.dst_addr_width);
>> >> +
>> >> + temp = src_datawidth << SPRD_DMA_SRC_DATAWIDTH_OFFSET;
>> >> + temp |= dst_datawidth << SPRD_DMA_DES_DATAWIDTH_OFFSET;
>> >> + temp |= slave_cfg->req_mode << SPRD_DMA_REQ_MODE_OFFSET;
>> >> + temp |= wrap_mode << SPRD_DMA_WRAP_SEL_OFFSET;
>> >> + temp |= wrap_en << SPRD_DMA_WRAP_EN_OFFSET;
>> >> + temp |= fix_mode << SPRD_DMA_FIX_SEL_OFFSET;
>> >> + temp |= fix_en << SPRD_DMA_FIX_EN_OFFSET;
>> >> + temp |= slave_cfg->cfg.src_maxburst & SPRD_DMA_FRG_LEN_MASK;
>> >> + hw->frg_len = temp;
>> >> +
>> >> + hw->blk_len = slave_cfg->block_len & SPRD_DMA_BLK_LEN_MASK;
>> >> + hw->trsc_len = slave_cfg->transcation_len & SPRD_DMA_TRSC_LEN_MASK;
>> >> +
>> >> + temp = (slave_cfg->dst_step & SPRD_DMA_TRSF_STEP_MASK) <<
>> >> + SPRD_DMA_DEST_TRSF_STEP_OFFSET;
>> >> + temp |= (slave_cfg->src_step & SPRD_DMA_TRSF_STEP_MASK) <<
>> >> + SPRD_DMA_SRC_TRSF_STEP_OFFSET;
>> >> + hw->trsf_step = temp;
>> >> +
>> >> + hw->frg_step = 0;
>> >> + hw->src_blk_step = 0;
>> >> + hw->des_blk_step = 0;
>> >> + return 0;
>> >> +}
>> >> +static struct dma_async_tx_descriptor *
>> >> +sprd_dma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>> >> + unsigned int sglen, enum dma_transfer_direction dir,
>> >> + unsigned long flags, void *context)
>> >> +{
>> >> + struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
>> >> + struct sprd_dma_config *slave_cfg = &schan->slave_cfg;
>> >> + u32 src_step = 0, dst_step = 0, len = 0;
>> >> + dma_addr_t src = 0, dst = 0;
>> >> + struct sprd_dma_desc *sdesc;
>> >> + struct scatterlist *sg;
>> >> + int ret, i;
>> >> +
>> >> + /* TODO: now we only support one sg for each DMA configuration. */
>> >> + if (!is_slave_direction(dir) || sglen > 1)
>> >> + return NULL;
>> >> +
>> >> + sdesc = kzalloc(sizeof(*sdesc), GFP_NOWAIT);
>> >> + if (!sdesc)
>> >> + return NULL;
>> >> +
>> >> + for_each_sg(sgl, sg, sglen, i) {
>> >> + len = sg_dma_len(sg);
>> >> +
>> >> + if (dir == DMA_MEM_TO_DEV) {
>> >> + src = sg_dma_address(sg);
>> >> + dst = slave_cfg->cfg.dst_addr;
>> >> + src_step = sprd_dma_get_step(slave_cfg->cfg.src_addr_width);
>> >> + dst_step = SPRD_DMA_NONE_STEP;
>> >> + } else {
>> >> + src = slave_cfg->cfg.src_addr;
>> >> + dst = sg_dma_address(sg);
>> >> + src_step = SPRD_DMA_NONE_STEP;
>> >> + dst_step = sprd_dma_get_step(slave_cfg->cfg.dst_addr_width);
>> >> + }
>> >> + }
>> >> +
>> >> + sprd_dma_fill_config(slave_cfg, src_step, dst_step, len, flags);
>> >> +
>> >> + ret = sprd_dma_config(chan, sdesc, src, dst, slave_cfg);
>> >> + if (ret) {
>> >> + kfree(sdesc);
>> >> + return NULL;
>> >> + }
>> >
>> > Am more intrigued here, the above call fills you config struct but you do not
>> > use it.. so what is the use of that.
>>
>> I did not get you here. We have passed the slave_cfg to
>> sprd_dma_config() to configure DMA hardware channel. Thanks.
>
> But you are not using that... So why bother configuring!
No, we used it. We use some configuration (src_maxburst, addr_width
and slave id) from slave_cfg to configure our DMA hardware channel.
>
> Again this is a channel specific data structure and not transaction specific.
> The values should go into descriptor and not something which is channel specific
Make sense.
--
Baolin.wang
Best Regards
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