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SubjectRe: [PATCH] dmaengine: sprd: Support DMA link-list mode
Hi Vinod,

(Comments from Eric Long)
On 9 August 2018 at 10:32, Vinod <vkoul@kernel.org> wrote:
> On 26-07-18, 16:00, Baolin Wang wrote:
>> From: Eric Long <eric.long@spreadtrum.com>
>>
>> The Spreadtrum DMA can support the link-list transaction mode, which means
>> DMA controller can do transaction one by one automatically once we linked
>> these transaction by link-list register.
>>
>> Signed-off-by: Eric Long <eric.long@spreadtrum.com>
>> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
>> ---
>> drivers/dma/sprd-dma.c | 82 ++++++++++++++++++++++++++++++++++++++----
>> include/linux/dma/sprd-dma.h | 69 +++++++++++++++++++++++++++++++++++
>> 2 files changed, 144 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
>> index 55df0d4..649bd2c 100644
>> --- a/drivers/dma/sprd-dma.c
>> +++ b/drivers/dma/sprd-dma.c
>> @@ -68,6 +68,7 @@
>>
>> /* SPRD_DMA_CHN_CFG register definition */
>> #define SPRD_DMA_CHN_EN BIT(0)
>> +#define SPRD_DMA_LINKLIST_EN BIT(4)
>> #define SPRD_DMA_WAIT_BDONE_OFFSET 24
>> #define SPRD_DMA_DONOT_WAIT_BDONE 1
>>
>> @@ -103,7 +104,7 @@
>> #define SPRD_DMA_REQ_MODE_MASK GENMASK(1, 0)
>> #define SPRD_DMA_FIX_SEL_OFFSET 21
>> #define SPRD_DMA_FIX_EN_OFFSET 20
>> -#define SPRD_DMA_LLIST_END_OFFSET 19
>> +#define SPRD_DMA_LLIST_END BIT(19)
>> #define SPRD_DMA_FRG_LEN_MASK GENMASK(16, 0)
>>
>> /* SPRD_DMA_CHN_BLK_LEN register definition */
>> @@ -164,6 +165,7 @@ struct sprd_dma_desc {
>> struct sprd_dma_chn {
>> struct virt_dma_chan vc;
>> void __iomem *chn_base;
>> + struct sprd_dma_linklist linklist;
>> struct dma_slave_config slave_cfg;
>> u32 chn_num;
>> u32 dev_id;
>> @@ -582,7 +584,8 @@ static int sprd_dma_get_step(enum dma_slave_buswidth buswidth)
>> }
>>
>> static int sprd_dma_fill_desc(struct dma_chan *chan,
>> - struct sprd_dma_desc *sdesc,
>> + struct sprd_dma_chn_hw *hw,
>> + unsigned int sglen, int sg_index,
>> dma_addr_t src, dma_addr_t dst, u32 len,
>> enum dma_transfer_direction dir,
>> unsigned long flags,
>> @@ -590,7 +593,6 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
>> {
>> 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 req_mode = (flags >> SPRD_DMA_REQ_SHIFT) & SPRD_DMA_REQ_MODE_MASK;
>> u32 int_mode = flags & SPRD_DMA_INT_MASK;
>> int src_datawidth, dst_datawidth, src_step, dst_step;
>> @@ -670,12 +672,58 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
>> temp |= (src_step & SPRD_DMA_TRSF_STEP_MASK) << SPRD_DMA_SRC_TRSF_STEP_OFFSET;
>> hw->trsf_step = temp;
>>
>> + /* link-list configuration */
>> + if (schan->linklist.phy_addr) {
>> + if (sg_index == sglen - 1)
>> + hw->frg_len |= SPRD_DMA_LLIST_END;
>> +
>> + hw->cfg |= SPRD_DMA_LINKLIST_EN;
>> + hw->llist_ptr = schan->linklist.phy_addr +
>> + ((sg_index + 1) % sglen) * sizeof(*hw) +
>> + SPRD_DMA_CHN_SRC_ADDR;
>> + } else {
>> + hw->llist_ptr = 0;
>> + }
>> +
>> hw->frg_step = 0;
>> hw->src_blk_step = 0;
>> hw->des_blk_step = 0;
>> return 0;
>> }
>>
>> +static int sprd_dma_fill_linklist_desc(struct dma_chan *chan,
>> + unsigned int sglen, int sg_index,
>> + dma_addr_t src, dma_addr_t dst, u32 len,
>> + enum dma_transfer_direction dir,
>> + unsigned long flags,
>> + struct dma_slave_config *slave_cfg)
>> +{
>> + struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
>> + struct sprd_dma_chn_hw *hw;
>> +
>> + if (sglen < 2 || !schan->linklist.virt_addr)
>> + return -EINVAL;
>
> why the limitation of 2 here?

Spreadtrum DMA link-list mode needs more than 2 link-list
configurations. If there is only one sg, it doesn't need to fill the
link-list configuration. Moreover, we have valided the sg length in
sprd_dma_prep_slave_sg(), so will remove the redundant validation
here.

>
>> +
>> + hw = (struct sprd_dma_chn_hw *)(schan->linklist.virt_addr +
>> + sg_index * sizeof(*hw));
>> +
>> + return sprd_dma_fill_desc(chan, hw, sglen, sg_index, src, dst, len, dir,
>> + flags, slave_cfg);
>> +}
>> +
>> +static int sprd_dma_fill_chn_desc(struct dma_chan *chan,
>> + struct sprd_dma_desc *sdesc,
>> + dma_addr_t src, dma_addr_t dst, u32 len,
>> + enum dma_transfer_direction dir,
>> + unsigned long flags,
>> + struct dma_slave_config *slave_cfg)
>> +{
>> + struct sprd_dma_chn_hw *hw = &sdesc->chn_hw;
>> +
>> + return sprd_dma_fill_desc(chan, hw, 0, 0, src, dst, len, dir,
>> + flags, slave_cfg);
>> +}
>
> this fn does not do much, so why not call sprd_dma_fill_desc() instead
> from caller!

OK, will fix it.

>
>> +
>> static struct dma_async_tx_descriptor *
>> sprd_dma_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
>> size_t len, unsigned long flags)
>> @@ -744,10 +792,20 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
>> u32 len = 0;
>> int ret, i;
>>
>> - /* TODO: now we only support one sg for each DMA configuration. */
>> - if (!is_slave_direction(dir) || sglen > 1)
>> + if (!is_slave_direction(dir))
>> return NULL;
>>
>> + if (context) {
>> + struct sprd_dma_linklist *ll_cfg =
>> + (struct sprd_dma_linklist *)context;
>> +
>> + schan->linklist.phy_addr = ll_cfg->phy_addr;
>> + schan->linklist.virt_addr = ll_cfg->virt_addr;
>> + } else {
>> + schan->linklist.phy_addr = 0;
>> + schan->linklist.virt_addr = 0;
>> + }
>> +
>> sdesc = kzalloc(sizeof(*sdesc), GFP_NOWAIT);
>> if (!sdesc)
>> return NULL;
>> @@ -762,10 +820,20 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
>> src = slave_cfg->src_addr;
>> dst = sg_dma_address(sg);
>> }
>> +
>> + if (sglen < 2)
>> + break;
>
> ?

Like I said above, dma link-list mode needs more than 2
configurations, I will add some comments to explain why.

>
>> +
>> + ret = sprd_dma_fill_linklist_desc(chan, sglen, i, src, dst, len,
>> + dir, flags, slave_cfg);
>> + if (ret) {
>> + kfree(sdesc);
>> + return NULL;
>> + }
>> }
>>
>> - ret = sprd_dma_fill_desc(chan, sdesc, src, dst, len, dir, flags,
>> - slave_cfg);
>> + ret = sprd_dma_fill_chn_desc(chan, sdesc, src, dst, len, dir, flags,
>> + slave_cfg);
>> if (ret) {
>> kfree(sdesc);
>> return NULL;
>> diff --git a/include/linux/dma/sprd-dma.h b/include/linux/dma/sprd-dma.h
>> index b0115e3..c51c705 100644
>> --- a/include/linux/dma/sprd-dma.h
>> +++ b/include/linux/dma/sprd-dma.h
>> @@ -58,4 +58,73 @@ enum sprd_dma_int_type {
>> SPRD_DMA_CFGERR_INT,
>> };
>>
>> +/*
>> + * struct sprd_dma_linklist - DMA link-list address structure
>> + * @virt_addr: link-list virtual address to configure link-list node
>> + * @phy_addr: link-list physical address to link DMA transfer
>> + *
>> + * The Spreadtrum DMA controller supports the link-list mode, that means slaves
>> + * can supply several groups configurations (each configuration represents one
>> + * DMA transfer) saved in memory, and DMA controller will link these groups
>> + * configurations by writing the physical address of each configuration into the
>> + * link-list register.
>> + *
>> + * Just as shown below, the link-list pointer register will be pointed to the
>> + * phycial address of 'configuration 1', and the 'configuration 1' link-list
>
> /s/phycial/physical

Sorry for typos and will fix.

>
>> + * pointer will be pointed to 'configuration 2', and so on.
>> + * Once trigger the DMA transfer, the DMA controller will load 'configureation
>
> /s/configureation/configuration

Will fix.

>
>> + * 1' to its registers automatically, after 'configuration 1' transation is
>
> /s/transation/transaction

Will fix.

>
>> + * done, DMA controller will load 'configuration 2' automatically, until all
>> + * DMA transactions are done.
>> + *
>> + * Note: The last link-list pointer should point to the physical address
>> + * of 'configuration 1', which can avoid DMA controller loads incorrect
>> + * configuration when the last configuration transaction is done.
>> + *
>> + * DMA controller linklist memory
>> + * ====================== -----------------------
>> + *| | | configuration 1 |<---
>> + *| DMA controller | ------->| | |
>> + *| | | | | |
>> + *| | | | | |
>> + *| | | | | |
>> + *| linklist pointer reg |---- ----| linklist pointer | |
>> + * ====================== | ----------------------- |
>> + * | |
>> + * | ----------------------- |
>> + * | | configuration 2 | |
>> + * --->| | |
>> + * | | |
>> + * | | |
>> + * | | |
>> + * ----| linklist pointer | |
>> + * | ----------------------- |
>> + * | |
>> + * | ----------------------- |
>> + * | | configuration 3 | |
>> + * --->| | |
>> + * | | |
>> + * | . | |
>> + * . |
>> + * . |
>> + * . |
>> + * | . |
>> + * | ----------------------- |
>> + * | | configuration n | |
>> + * --->| | |
>> + * | | |
>> + * | | |
>> + * | | |
>> + * | linklist pointer |----
>> + * -----------------------
>> + *
>> + * To support the link-list mode, DMA slaves should allocate one segment memory
>> + * from always-on IRAM or dma coherent memory to store these groups of DMA
>> + * configuration, and pass the virtual and physical addess to DMA controller.
>
> /s/addess/address

Will fix in next version. Thanks for your comments.

--
Baolin Wang
Best Regards

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