Re: [PATCH v5 02/10] dmaengine: Actions: get rid of bit fields from dma descriptor

From: Manivannan Sadhasivam
Date: Sun Jul 12 2020 - 13:11:12 EST

On Thu, Jul 02, 2020 at 08:22:48PM +0530, Amit Singh Tomar wrote:
> At the moment, Driver uses bit fields to describe registers of the DMA
> descriptor structure that makes it less portable and maintainable, and
> Andre suugested(and even sketched important bits for it) to make use of
> array to describe this DMA descriptors instead. It gives the flexibility
> while extending support for other platform such as Actions S700.
>
> This commit removes the "owl_dma_lli_hw" (that includes bit-fields) and
> uses array to describe DMA descriptor.
>
> Suggested-by: Andre Przywara <andre.przywara@xxxxxxx>
> Signed-off-by: Amit Singh Tomar <amittomer25@xxxxxxxxx>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>

Thanks,
Mani

> ---
> Changes since v4:
> * Reordered it from 01/10 to 02/10.
> Changes since v3:
> * Added description for enum fields.
> * Restored the old comment.
> * Added detailed comment about, the way FLEN
> and FCNT values are filled.
> Changes since v2:
> * No change.
> Changes since v1:
> * Defined macro for frame count value.
> * Introduced llc_hw_flen() from patch 2/9.
> * Removed the unnecessary line break.
> Changes since rfc:
> * No change.
> ---
> drivers/dma/owl-dma.c | 98 +++++++++++++++++++++++++++++----------------------
> 1 file changed, 56 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/dma/owl-dma.c b/drivers/dma/owl-dma.c
> index 66ef70b00ec0..948d1bead860 100644
> --- a/drivers/dma/owl-dma.c
> +++ b/drivers/dma/owl-dma.c
> @@ -120,30 +120,33 @@
> #define BIT_FIELD(val, width, shift, newshift) \
> ((((val) >> (shift)) & ((BIT(width)) - 1)) << (newshift))
>
> +/* Frame count value is fixed as 1 */
> +#define FCNT_VAL 0x1
> +
> /**
> - * struct owl_dma_lli_hw - Hardware link list for dma transfer
> - * @next_lli: physical address of the next link list
> - * @saddr: source physical address
> - * @daddr: destination physical address
> - * @flen: frame length
> - * @fcnt: frame count
> - * @src_stride: source stride
> - * @dst_stride: destination stride
> - * @ctrla: dma_mode and linklist ctrl config
> - * @ctrlb: interrupt config
> - * @const_num: data for constant fill
> + * owl_dmadesc_offsets - Describe DMA descriptor, hardware link
> + * list for dma transfer
> + * @OWL_DMADESC_NEXT_LLI: physical address of the next link list
> + * @OWL_DMADESC_SADDR: source physical address
> + * @OWL_DMADESC_DADDR: destination physical address
> + * @OWL_DMADESC_FLEN: frame length
> + * @OWL_DMADESC_SRC_STRIDE: source stride
> + * @OWL_DMADESC_DST_STRIDE: destination stride
> + * @OWL_DMADESC_CTRLA: dma_mode and linklist ctrl config
> + * @OWL_DMADESC_CTRLB: interrupt config
> + * @OWL_DMADESC_CONST_NUM: data for constant fill
> */
> -struct owl_dma_lli_hw {
> - u32 next_lli;
> - u32 saddr;
> - u32 daddr;
> - u32 flen:20;
> - u32 fcnt:12;
> - u32 src_stride;
> - u32 dst_stride;
> - u32 ctrla;
> - u32 ctrlb;
> - u32 const_num;
> +enum owl_dmadesc_offsets {
> + OWL_DMADESC_NEXT_LLI = 0,
> + OWL_DMADESC_SADDR,
> + OWL_DMADESC_DADDR,
> + OWL_DMADESC_FLEN,
> + OWL_DMADESC_SRC_STRIDE,
> + OWL_DMADESC_DST_STRIDE,
> + OWL_DMADESC_CTRLA,
> + OWL_DMADESC_CTRLB,
> + OWL_DMADESC_CONST_NUM,
> + OWL_DMADESC_SIZE
> };
>
> /**
> @@ -153,7 +156,7 @@ struct owl_dma_lli_hw {
> * @node: node for txd's lli_list
> */
> struct owl_dma_lli {
> - struct owl_dma_lli_hw hw;
> + u32 hw[OWL_DMADESC_SIZE];
> dma_addr_t phys;
> struct list_head node;
> };
> @@ -318,6 +321,11 @@ static inline u32 llc_hw_ctrlb(u32 int_ctl)
> return ctl;
> }
>
> +static u32 llc_hw_flen(struct owl_dma_lli *lli)
> +{
> + return lli->hw[OWL_DMADESC_FLEN] & GENMASK(19, 0);
> +}
> +
> static void owl_dma_free_lli(struct owl_dma *od,
> struct owl_dma_lli *lli)
> {
> @@ -349,8 +357,9 @@ static struct owl_dma_lli *owl_dma_add_lli(struct owl_dma_txd *txd,
> list_add_tail(&next->node, &txd->lli_list);
>
> if (prev) {
> - prev->hw.next_lli = next->phys;
> - prev->hw.ctrla |= llc_hw_ctrla(OWL_DMA_MODE_LME, 0);
> + prev->hw[OWL_DMADESC_NEXT_LLI] = next->phys;
> + prev->hw[OWL_DMADESC_CTRLA] |=
> + llc_hw_ctrla(OWL_DMA_MODE_LME, 0);
> }
>
> return next;
> @@ -363,8 +372,7 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
> struct dma_slave_config *sconfig,
> bool is_cyclic)
> {
> - struct owl_dma_lli_hw *hw = &lli->hw;
> - u32 mode;
> + u32 mode, ctrlb;
>
> mode = OWL_DMA_MODE_PW(0);
>
> @@ -405,22 +413,28 @@ static inline int owl_dma_cfg_lli(struct owl_dma_vchan *vchan,
> return -EINVAL;
> }
>
> - hw->next_lli = 0; /* One link list by default */
> - hw->saddr = src;
> - hw->daddr = dst;
> -
> - hw->fcnt = 1; /* Frame count fixed as 1 */
> - hw->flen = len; /* Max frame length is 1MB */
> - hw->src_stride = 0;
> - hw->dst_stride = 0;
> - hw->ctrla = llc_hw_ctrla(mode,
> - OWL_DMA_LLC_SAV_LOAD_NEXT |
> - OWL_DMA_LLC_DAV_LOAD_NEXT);
> + lli->hw[OWL_DMADESC_CTRLA] = llc_hw_ctrla(mode,
> + OWL_DMA_LLC_SAV_LOAD_NEXT |
> + OWL_DMA_LLC_DAV_LOAD_NEXT);
>
> if (is_cyclic)
> - hw->ctrlb = llc_hw_ctrlb(OWL_DMA_INTCTL_BLOCK);
> + ctrlb = llc_hw_ctrlb(OWL_DMA_INTCTL_BLOCK);
> else
> - hw->ctrlb = llc_hw_ctrlb(OWL_DMA_INTCTL_SUPER_BLOCK);
> + ctrlb = llc_hw_ctrlb(OWL_DMA_INTCTL_SUPER_BLOCK);
> +
> + lli->hw[OWL_DMADESC_NEXT_LLI] = 0; /* One link list by default */
> + lli->hw[OWL_DMADESC_SADDR] = src;
> + lli->hw[OWL_DMADESC_DADDR] = dst;
> + lli->hw[OWL_DMADESC_SRC_STRIDE] = 0;
> + lli->hw[OWL_DMADESC_DST_STRIDE] = 0;
> + /*
> + * Word starts from offset 0xC is shared between frame length
> + * (max frame length is 1MB) and frame count, where first 20
> + * bits are for frame length and rest of 12 bits are for frame
> + * count.
> + */
> + lli->hw[OWL_DMADESC_FLEN] = len | FCNT_VAL << 20;
> + lli->hw[OWL_DMADESC_CTRLB] = ctrlb;
>
> return 0;
> }
> @@ -752,7 +766,7 @@ static u32 owl_dma_getbytes_chan(struct owl_dma_vchan *vchan)
> /* Start from the next active node */
> if (lli->phys == next_lli_phy) {
> list_for_each_entry(lli, &txd->lli_list, node)
> - bytes += lli->hw.flen;
> + bytes += llc_hw_flen(lli);
> break;
> }
> }
> @@ -783,7 +797,7 @@ static enum dma_status owl_dma_tx_status(struct dma_chan *chan,
> if (vd) {
> txd = to_owl_txd(&vd->tx);
> list_for_each_entry(lli, &txd->lli_list, node)
> - bytes += lli->hw.flen;
> + bytes += llc_hw_flen(lli);
> } else {
> bytes = owl_dma_getbytes_chan(vchan);
> }
> --
> 2.7.4
>