From ce56098eb4dc2985f27f30ad7b7f5aed6bcf7fb1 Mon Sep 17 00:00:00 2001 From: Jonathan Bell Date: Fri, 19 Jul 2024 15:55:56 +0100 Subject: [PATCH 1193/1215] drivers: dw-axi-dmac: make more sensible choices about memory accesses There's no real need to constrain MEM access widths to 32-bit (or narrower), as the DMAC is intelligent enough to size memory accesses appropriately. Wider accesses are more efficient. Similarly, MEM burst lengths don't need to be a function of DEV burst lengths - the DMAC packs/unpacks data into/from its internal channel FIFOs appropriately. Longer accesses are more efficient. However, the DMAC doesn't have complete support for unaligned accesses, and blocks are always defined in integer multiples of SRC_WIDTH, so odd source lengths or buffer alignments will prevent wide accesses being used, as before. There is an implicit requirement to limit requested DEV read burst lengths to less than the hardware's maximum configured MSIZE - otherwise RX data will be left over at the end of a block. There is no config register that reports this value, so the AXI burst length parameter is used to produce a facsimile of it. Warn if such a request arrives that doesn't respect this. Signed-off-by: Jonathan Bell --- .../dma/dw-axi-dmac/dw-axi-dmac-platform.c | 38 ++++++++++++------- 1 file changed, 25 insertions(+), 13 deletions(-) --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c @@ -261,6 +261,15 @@ static u32 axi_chan_get_xfer_width(struc return __ffs(src | dst | len | BIT(max_width)); } +static u32 axi_dma_encode_msize(u32 max_burst) +{ + if (max_burst <= 1) + return DWAXIDMAC_BURST_TRANS_LEN_1; + if (max_burst > 1024) + return DWAXIDMAC_BURST_TRANS_LEN_1024; + return fls(max_burst) - 2; +} + static inline const char *axi_chan_name(struct axi_dma_chan *chan) { return dma_chan_name(&chan->vc.chan); @@ -685,41 +694,41 @@ static int dw_axi_dma_set_hw_desc(struct size_t axi_block_ts; size_t block_ts; u32 ctllo, ctlhi; - u32 burst_len; + u32 burst_len = 0, mem_burst_msize, reg_burst_msize; axi_block_ts = chan->chip->dw->hdata->block_size[chan->id]; mem_width = __ffs(data_width | mem_addr | len); - if (mem_width > DWAXIDMAC_TRANS_WIDTH_32) - mem_width = DWAXIDMAC_TRANS_WIDTH_32; if (!IS_ALIGNED(mem_addr, 4)) { dev_err(chan->chip->dev, "invalid buffer alignment\n"); return -EINVAL; } + /* Use a reasonable upper limit otherwise residue reporting granularity grows large */ + mem_burst_msize = axi_dma_encode_msize(16); + switch (chan->direction) { case DMA_MEM_TO_DEV: + reg_burst_msize = axi_dma_encode_msize(chan->config.dst_maxburst); reg_width = __ffs(chan->config.dst_addr_width); device_addr = phys_to_dma(chan->chip->dev, chan->config.dst_addr); ctllo = reg_width << CH_CTL_L_DST_WIDTH_POS | mem_width << CH_CTL_L_SRC_WIDTH_POS | - DWAXIDMAC_BURST_TRANS_LEN_1 << CH_CTL_L_DST_MSIZE_POS | - DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_SRC_MSIZE_POS | + reg_burst_msize << CH_CTL_L_DST_MSIZE_POS | + mem_burst_msize << CH_CTL_L_SRC_MSIZE_POS | DWAXIDMAC_CH_CTL_L_NOINC << CH_CTL_L_DST_INC_POS | DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_SRC_INC_POS; block_ts = len >> mem_width; break; case DMA_DEV_TO_MEM: + reg_burst_msize = axi_dma_encode_msize(chan->config.src_maxburst); reg_width = __ffs(chan->config.src_addr_width); - /* Prevent partial access units getting lost */ - if (mem_width > reg_width) - mem_width = reg_width; device_addr = phys_to_dma(chan->chip->dev, chan->config.src_addr); ctllo = reg_width << CH_CTL_L_SRC_WIDTH_POS | mem_width << CH_CTL_L_DST_WIDTH_POS | - DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_DST_MSIZE_POS | - DWAXIDMAC_BURST_TRANS_LEN_1 << CH_CTL_L_SRC_MSIZE_POS | + mem_burst_msize << CH_CTL_L_DST_MSIZE_POS | + reg_burst_msize << CH_CTL_L_SRC_MSIZE_POS | DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_DST_INC_POS | DWAXIDMAC_CH_CTL_L_NOINC << CH_CTL_L_SRC_INC_POS; block_ts = len >> reg_width; @@ -760,6 +769,12 @@ static int dw_axi_dma_set_hw_desc(struct set_desc_src_master(hw_desc); hw_desc->len = len; + + if (burst_len && (chan->config.src_maxburst > burst_len)) + dev_warn_ratelimited(chan2dev(chan), + "%s: requested source burst length %u exceeds supported burst length %u - data may be lost\n", + axi_chan_name(chan), chan->config.src_maxburst, burst_len); + return 0; } @@ -776,9 +791,6 @@ static size_t calculate_block_len(struct case DMA_MEM_TO_DEV: data_width = BIT(chan->chip->dw->hdata->m_data_width); mem_width = __ffs(data_width | dma_addr | buf_len); - if (mem_width > DWAXIDMAC_TRANS_WIDTH_32) - mem_width = DWAXIDMAC_TRANS_WIDTH_32; - block_len = axi_block_ts << mem_width; break; case DMA_DEV_TO_MEM: