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Message-ID: <1dcd57be-0c97-2025-ff01-42b086833357@codeaurora.org>
Date: Fri, 4 Aug 2017 11:24:55 +0530
From: Archit Taneja <architt@...eaurora.org>
To: Abhishek Sahu <absahu@...eaurora.org>, dwmw2@...radead.org,
computersforpeace@...il.com, boris.brezillon@...e-electrons.com,
marek.vasut@...il.com, richard@....at, cyrille.pitchen@...ev4u.fr,
robh+dt@...nel.org, mark.rutland@....com
Cc: linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
andy.gross@...aro.org, sricharan@...eaurora.org
Subject: Re: [PATCH v2 17/25] mtd: nand: qcom: add BAM DMA descriptor handling
On 07/19/2017 05:18 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.
Reviewed-by: Archit Taneja <architt@...eaurora.org>
>
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
> drivers/mtd/nand/qcom_nandc.c | 143 ++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 130 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
> index fc29c97..589108b 100644
> --- a/drivers/mtd/nand/qcom_nandc.c
> +++ b/drivers/mtd/nand/qcom_nandc.c
> @@ -209,14 +209,23 @@ 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
> + * @adm_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 adm_sgl;
> + struct {
> + struct scatterlist *bam_sgl;
> + int sgl_cnt;
> + };
> + };
> struct dma_async_tx_descriptor *dma_desc;
> };
>
> @@ -580,9 +589,77 @@ static void update_rw_regs(struct qcom_nand_host *host, int num_cw, bool read)
> nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
> }
>
> -static int prep_dma_desc(struct qcom_nand_controller *nandc, bool read,
> - int reg_off, const void *vaddr, int size,
> - bool flow_control)
> +/*
> + * 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)
> +{
> + struct desc_info *desc;
> + struct scatterlist *sgl;
> + unsigned int sgl_cnt;
> + int ret;
> + 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_sgl[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_sgl[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);
> + ret = dma_map_sg(nandc->dev, sgl, sgl_cnt, desc->dir);
> + if (ret == 0) {
> + dev_err(nandc->dev, "failure in mapping desc\n");
> + kfree(desc);
> + return -ENOMEM;
> + }
> +
> + 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_adm_dma_desc(struct qcom_nand_controller *nandc, bool read,
> + int reg_off, const void *vaddr, int size,
> + bool flow_control)
> {
> struct desc_info *desc;
> struct dma_async_tx_descriptor *dma_desc;
> @@ -595,7 +672,7 @@ static int prep_dma_desc(struct qcom_nand_controller *nandc, bool read,
> if (!desc)
> return -ENOMEM;
>
> - sgl = &desc->sgl;
> + sgl = &desc->adm_sgl;
>
> sg_init_one(sgl, vaddr, size);
>
> @@ -671,7 +748,7 @@ static int read_reg_dma(struct qcom_nand_controller *nandc, int first,
> vaddr = nandc->reg_read_buf + nandc->reg_read_pos;
> nandc->reg_read_pos += num_regs;
>
> - return prep_dma_desc(nandc, true, first, vaddr, size, flow_control);
> + return prep_adm_dma_desc(nandc, true, first, vaddr, size, flow_control);
> }
>
> /*
> @@ -702,7 +779,8 @@ static int write_reg_dma(struct qcom_nand_controller *nandc, int first,
>
> size = num_regs * sizeof(u32);
>
> - return prep_dma_desc(nandc, false, first, vaddr, size, flow_control);
> + return prep_adm_dma_desc(nandc, false, first, vaddr, size,
> + flow_control);
> }
>
> /*
> @@ -716,7 +794,7 @@ static int write_reg_dma(struct qcom_nand_controller *nandc, int first,
> static int read_data_dma(struct qcom_nand_controller *nandc, int reg_off,
> const u8 *vaddr, int size)
> {
> - return prep_dma_desc(nandc, true, reg_off, vaddr, size, false);
> + return prep_adm_dma_desc(nandc, true, reg_off, vaddr, size, false);
> }
>
> /*
> @@ -730,7 +808,7 @@ static int read_data_dma(struct qcom_nand_controller *nandc, int reg_off,
> static int write_data_dma(struct qcom_nand_controller *nandc, int reg_off,
> const u8 *vaddr, int size)
> {
> - return prep_dma_desc(nandc, false, reg_off, vaddr, size, false);
> + return prep_adm_dma_desc(nandc, false, reg_off, vaddr, size, false);
> }
>
> /*
> @@ -930,12 +1008,44 @@ 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->props->is_bam) {
> + if (bam_txn->rx_sgl_pos > bam_txn->rx_sgl_start) {
> + 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->props->is_bam) {
> + 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;
> }
> @@ -946,7 +1056,14 @@ 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->props->is_bam)
> + dma_unmap_sg(nandc->dev, desc->bam_sgl,
> + desc->sgl_cnt, desc->dir);
> + else
> + dma_unmap_sg(nandc->dev, &desc->adm_sgl, 1,
> + desc->dir);
> +
> kfree(desc);
> }
> }
>
--
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