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SubjectRe: [PATCH 06/14] qcom: mtd: nand: add bam dma descriptor handling
On 2017-07-04 11:40, Archit Taneja wrote:
> On 06/29/2017 12:45 PM, Abhishek Sahu wrote:
>> 1. prepare_bam_async_desc is the function which will call
>> all the DMA API’s. It will fetch the outstanding scatter gather
>> list for passed channel and will do the DMA descriptor formation.
>> The DMA flag is dependent upon the type of channel.
>>
>> 2. For ADM DMA, the descriptor is being formed for every DMA
>> request so its sgl count will be always 1 while in BAM DMA, the
>> clubbing of descriptor is being done to increase throughput.
>>
>> 3. ADM uses only one channel while in BAM, data descriptors
>> will be submitted to tx channel (for write) or rx channel
>> (for read) and all the registers read/write descriptors in
>> command channel.
>>
>> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
>> ---
>> drivers/mtd/nand/qcom_nandc.c | 119
>> ++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 114 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/qcom_nandc.c
>> b/drivers/mtd/nand/qcom_nandc.c
>> index f8d0bde..7042a65 100644
>> --- a/drivers/mtd/nand/qcom_nandc.c
>> +++ b/drivers/mtd/nand/qcom_nandc.c
>> @@ -206,14 +206,22 @@ struct bam_transaction {
>> * This data type corresponds to the nand dma descriptor
>> * @list - list for desc_info
>> * @dir - DMA transfer direction
>> - * @sgl - sgl which will be used for single sgl dma descriptor
>> + * @sgl - sgl which will be used for single sgl dma descriptor. Only
>> used by ADM
>> + * @bam_sgl - sgl which will be used for dma descriptor. Only used by
>> BAM
>> + * @sgl_cnt - number of SGL in bam_sgl. Only used by BAM
>> * @dma_desc - low level dma engine descriptor
>> */
>> struct desc_info {
>> struct list_head node;
>>
>> enum dma_data_direction dir;
>> - struct scatterlist sgl;
>> + union {
>> + struct scatterlist sgl;
>
> Can you make this adm_sgl instead for consistency? Also, please use
> only
> two tabs instead of one here for indentation.

Sure. I will do the same in v2.

>
>> + struct {
>> + struct scatterlist *bam_sgl;
>> + int sgl_cnt;
>> + };
>> + };
>> struct dma_async_tx_descriptor *dma_desc;
>> };
>>
>> @@ -564,6 +572,68 @@ static void update_rw_regs(struct qcom_nand_host
>> *host, int num_cw, bool read)
>> nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
>> }
>>
>> +/*
>> + * Maps the scatter gather list for DMA transfer and forms the DMA
>> descriptor
>> + * for BAM. This descriptor will be added in the NAND DMA descriptor
>> queue
>> + * which will be submitted to DMA engine.
>> + */
>> +static int prepare_bam_async_desc(struct qcom_nand_controller *nandc,
>> + struct dma_chan *chan,
>> + unsigned long flags)
>
> From what I gathered in patch #10, this would be called by
> prep_dma_desc_data_bam() and prep_dma_desc_command(). Can you rename
> these
> two to something like prep_bam_dma_desc_data() and
> prep_bam_dma_desc_cmd()
>

Sure. I will do the same in v2.

>
>> +{
>> + struct desc_info *desc;
>> + struct scatterlist *sgl;
>> + unsigned int sgl_cnt;
>> + struct bam_transaction *bam_txn = nandc->bam_txn;
>> + enum dma_transfer_direction dir_eng;
>> + struct dma_async_tx_descriptor *dma_desc;
>> +
>> + desc = kzalloc(sizeof(*desc), GFP_KERNEL);
>> + if (!desc)
>> + return -ENOMEM;
>> +
>> + if (chan == nandc->cmd_chan) {
>> + sgl = &bam_txn->cmd_sgl[bam_txn->cmd_sgl_start];
>> + sgl_cnt = bam_txn->cmd_sgl_pos - bam_txn->cmd_sgl_start;
>> + bam_txn->cmd_sgl_start = bam_txn->cmd_sgl_pos;
>> + dir_eng = DMA_MEM_TO_DEV;
>> + desc->dir = DMA_TO_DEVICE;
>> + } else if (chan == nandc->tx_chan) {
>> + sgl = &bam_txn->data_sg[bam_txn->tx_sgl_start];
>> + sgl_cnt = bam_txn->tx_sgl_pos - bam_txn->tx_sgl_start;
>> + bam_txn->tx_sgl_start = bam_txn->tx_sgl_pos;
>> + dir_eng = DMA_MEM_TO_DEV;
>> + desc->dir = DMA_TO_DEVICE;
>> + } else {
>> + sgl = &bam_txn->data_sg[bam_txn->rx_sgl_start];
>> + sgl_cnt = bam_txn->rx_sgl_pos - bam_txn->rx_sgl_start;
>> + bam_txn->rx_sgl_start = bam_txn->rx_sgl_pos;
>> + desc->dir = DMA_FROM_DEVICE;
>> + dir_eng = DMA_DEV_TO_MEM;
>> + }
>> +
>> + sg_mark_end(sgl + sgl_cnt - 1);
>> + dma_map_sg(nandc->dev, sgl, sgl_cnt, desc->dir);
>
> Is it safe to assume here that dma_map_sg won't return an error?
>

We need to check for error. I will fix this in v2.

>> +
>> + desc->sgl_cnt = sgl_cnt;
>> + desc->bam_sgl = sgl;
>> +
>> + dma_desc = dmaengine_prep_slave_sg(chan, sgl, sgl_cnt, dir_eng,
>> + flags);
>> +
>> + if (!dma_desc) {
>> + dev_err(nandc->dev, "failure in prep desc\n");
>> + kfree(desc);
>> + return -EINVAL;
>> + }
>> +
>> + desc->dma_desc = dma_desc;
>> +
>> + list_add_tail(&desc->node, &nandc->desc_list);
>> +
>> + return 0;
>> +}
>> +
>
>
>> static int prep_dma_desc(struct qcom_nand_controller *nandc, bool
>> read,
>> int reg_off, const void *vaddr, int size,
>> bool flow_control)
>
> Could you rename this to prep_adm_dma_desc for consistency?
>
>> @@ -891,12 +961,44 @@ static int submit_descs(struct
>> qcom_nand_controller *nandc)
>> {
>> struct desc_info *desc;
>> dma_cookie_t cookie = 0;
>> + struct bam_transaction *bam_txn = nandc->bam_txn;
>> + int r;
>> +
>> + if (nandc->dma_bam_enabled) {
>> + if (bam_txn->rx_sgl_pos - bam_txn->rx_sgl_start) {
>
> Using '>' instead of '-' here should be more legible.
>

Yes. I will use the same in v2.

>> + r = prepare_bam_async_desc(nandc, nandc->rx_chan, 0);
>> + if (r)
>> + return r;
>> + }
>> +
>> + if (bam_txn->tx_sgl_pos - bam_txn->tx_sgl_start) {
>> + r = prepare_bam_async_desc(nandc, nandc->tx_chan,
>> + DMA_PREP_INTERRUPT);
>> + if (r)
>> + return r;
>> + }
>> +
>> + if (bam_txn->cmd_sgl_pos - bam_txn->cmd_sgl_start) {
>> + r = prepare_bam_async_desc(nandc, nandc->cmd_chan,
>> + DMA_PREP_CMD);
>> + if (r)
>> + return r;
>> + }
>> + }
>>
>> list_for_each_entry(desc, &nandc->desc_list, node)
>> cookie = dmaengine_submit(desc->dma_desc);
>>
>> - if (dma_sync_wait(nandc->chan, cookie) != DMA_COMPLETE)
>> - return -ETIMEDOUT;
>> + if (nandc->dma_bam_enabled) {
>> + dma_async_issue_pending(nandc->tx_chan);
>> + dma_async_issue_pending(nandc->rx_chan);
>> +
>> + if (dma_sync_wait(nandc->cmd_chan, cookie) != DMA_COMPLETE)
>> + return -ETIMEDOUT;
>> + } else {
>> + if (dma_sync_wait(nandc->chan, cookie) != DMA_COMPLETE)
>> + return -ETIMEDOUT;
>> + }
>>
>> return 0;
>> }
>> @@ -907,7 +1009,14 @@ static void free_descs(struct
>> qcom_nand_controller *nandc)
>>
>> list_for_each_entry_safe(desc, n, &nandc->desc_list, node) {
>> list_del(&desc->node);
>> - dma_unmap_sg(nandc->dev, &desc->sgl, 1, desc->dir);
>> +
>> + if (nandc->dma_bam_enabled)
>> + dma_unmap_sg(nandc->dev, desc->bam_sgl,
>> + desc->sgl_cnt, desc->dir);
>> + else
>> + dma_unmap_sg(nandc->dev, &desc->sgl, 1,
>> + desc->dir);
>> +
>> kfree(desc);
>> }
>> }
>>

--
Abhishek Sahu

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