Re: [PATCH RFC 1/8] dmaengine: Actions: get rid of bit fields from dma descriptor
From: Manivannan Sadhasivam <hidden>
Date: 2020-05-10 15:52:15
Also in:
dmaengine
Hi, On Wed, May 06, 2020 at 04:06:03PM +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.
I'm in favor of getting rid of bitfields due to its not so defined way of working (and forgive me for using it in first place) but I don't quite like the current approach. Rather I'd like to have custom bitmasks (S900/S700/S500?) for writing to those fields. Thanks, Mani
quoted hunk ↗ jump to hunk
Suggested-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Amit Singh Tomar <redacted> --- drivers/dma/owl-dma.c | 77 ++++++++++++++++++++++----------------------------- 1 file changed, 33 insertions(+), 44 deletions(-)diff --git a/drivers/dma/owl-dma.c b/drivers/dma/owl-dma.c index c683051257fd..b0d80a2fa383 100644 --- a/drivers/dma/owl-dma.c +++ b/drivers/dma/owl-dma.c@@ -120,30 +120,18 @@ #define BIT_FIELD(val, width, shift, newshift) \ ((((val) >> (shift)) & ((BIT(width)) - 1)) << (newshift)) -/** - * 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 - */ -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; +/* Describe DMA descriptor, hardware link list for dma transfer */ +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 +141,7 @@ 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; };@@ -351,8 +339,9 @@ 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;@@ -365,8 +354,7 @@ 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);@@ -407,22 +395,22 @@ 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; + 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; + lli->hw[OWL_DMADESC_FLEN] = len | 1 << 20; + lli->hw[OWL_DMADESC_CTRLB] = ctrlb; return 0; }@@ -754,7 +742,8 @@ 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 += lli->hw[OWL_DMADESC_FLEN] & + GENMASK(19, 0); break; } }@@ -785,7 +774,7 @@ 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 += lli->hw[OWL_DMADESC_FLEN] & GENMASK(19, 0); } else { bytes = owl_dma_getbytes_chan(vchan); }-- 2.7.4
_______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel