git.openwrt.org Git - openwrt/staging/linusw.git/blob

   1 From ce56098eb4dc2985f27f30ad7b7f5aed6bcf7fb1 Mon Sep 17 00:00:00 2001
   2 From: Jonathan Bell <jonathan@raspberrypi.com>
   3 Date: Fri, 19 Jul 2024 15:55:56 +0100
   4 Subject: [PATCH 1193/1215] drivers: dw-axi-dmac: make more sensible choices
   5  about memory accesses
   6
   7 There's no real need to constrain MEM access widths to 32-bit (or
   8 narrower), as the DMAC is intelligent enough to size memory accesses
   9 appropriately. Wider accesses are more efficient.
  10
  11 Similarly, MEM burst lengths don't need to be a function of DEV burst
  12 lengths - the DMAC packs/unpacks data into/from its internal channel
  13 FIFOs appropriately. Longer accesses are more efficient.
  14
  15 However, the DMAC doesn't have complete support for unaligned accesses,
  16 and blocks are always defined in integer multiples of SRC_WIDTH, so odd
  17 source lengths or buffer alignments will prevent wide accesses being
  18 used, as before.
  19
  20 There is an implicit requirement to limit requested DEV read burst
  21 lengths to less than the hardware's maximum configured MSIZE - otherwise
  22 RX data will be left over at the end of a block. There is no config
  23 register that reports this value, so the AXI burst length parameter is
  24 used to produce a facsimile of it. Warn if such a request arrives that
  25 doesn't respect this.
  26
  27 Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
  28 ---
  29  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    | 38 ++++++++++++-------
  30  1 file changed, 25 insertions(+), 13 deletions(-)
  31
  32 --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
  33 +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
  34 @@ -261,6 +261,15 @@ static u32 axi_chan_get_xfer_width(struc
  35         return __ffs(src | dst | len | BIT(max_width));
  36  }
  37
  38 +static u32 axi_dma_encode_msize(u32 max_burst)
  39 +{
  40 +       if (max_burst <= 1)
  41 +               return DWAXIDMAC_BURST_TRANS_LEN_1;
  42 +       if (max_burst > 1024)
  43 +               return DWAXIDMAC_BURST_TRANS_LEN_1024;
  44 +       return fls(max_burst) - 2;
  45 +}
  46 +
  47  static inline const char *axi_chan_name(struct axi_dma_chan *chan)
  48  {
  49         return dma_chan_name(&chan->vc.chan);
  50 @@ -685,41 +694,41 @@ static int dw_axi_dma_set_hw_desc(struct
  51         size_t axi_block_ts;
  52         size_t block_ts;
  53         u32 ctllo, ctlhi;
  54 -       u32 burst_len;
  55 +       u32 burst_len = 0, mem_burst_msize, reg_burst_msize;
  56
  57         axi_block_ts = chan->chip->dw->hdata->block_size[chan->id];
  58
  59         mem_width = __ffs(data_width | mem_addr | len);
  60 -       if (mem_width > DWAXIDMAC_TRANS_WIDTH_32)
  61 -               mem_width = DWAXIDMAC_TRANS_WIDTH_32;
  62
  63         if (!IS_ALIGNED(mem_addr, 4)) {
  64                 dev_err(chan->chip->dev, "invalid buffer alignment\n");
  65                 return -EINVAL;
  66         }
  67
  68 +       /* Use a reasonable upper limit otherwise residue reporting granularity grows large */
  69 +       mem_burst_msize = axi_dma_encode_msize(16);
  70 +
  71         switch (chan->direction) {
  72         case DMA_MEM_TO_DEV:
  73 +               reg_burst_msize = axi_dma_encode_msize(chan->config.dst_maxburst);
  74                 reg_width = __ffs(chan->config.dst_addr_width);
  75                 device_addr = phys_to_dma(chan->chip->dev, chan->config.dst_addr);
  76                 ctllo = reg_width << CH_CTL_L_DST_WIDTH_POS |
  77                         mem_width << CH_CTL_L_SRC_WIDTH_POS |
  78 -                       DWAXIDMAC_BURST_TRANS_LEN_1 << CH_CTL_L_DST_MSIZE_POS |
  79 -                       DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_SRC_MSIZE_POS |
  80 +                       reg_burst_msize << CH_CTL_L_DST_MSIZE_POS |
  81 +                       mem_burst_msize << CH_CTL_L_SRC_MSIZE_POS |
  82                         DWAXIDMAC_CH_CTL_L_NOINC << CH_CTL_L_DST_INC_POS |
  83                         DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_SRC_INC_POS;
  84                 block_ts = len >> mem_width;
  85                 break;
  86         case DMA_DEV_TO_MEM:
  87 +               reg_burst_msize = axi_dma_encode_msize(chan->config.src_maxburst);
  88                 reg_width = __ffs(chan->config.src_addr_width);
  89 -               /* Prevent partial access units getting lost */
  90 -               if (mem_width > reg_width)
  91 -                       mem_width = reg_width;
  92                 device_addr = phys_to_dma(chan->chip->dev, chan->config.src_addr);
  93                 ctllo = reg_width << CH_CTL_L_SRC_WIDTH_POS |
  94                         mem_width << CH_CTL_L_DST_WIDTH_POS |
  95 -                       DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_DST_MSIZE_POS |
  96 -                       DWAXIDMAC_BURST_TRANS_LEN_1 << CH_CTL_L_SRC_MSIZE_POS |
  97 +                       mem_burst_msize << CH_CTL_L_DST_MSIZE_POS |
  98 +                       reg_burst_msize << CH_CTL_L_SRC_MSIZE_POS |
  99                         DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_DST_INC_POS |
 100                         DWAXIDMAC_CH_CTL_L_NOINC << CH_CTL_L_SRC_INC_POS;
 101                 block_ts = len >> reg_width;
 102 @@ -760,6 +769,12 @@ static int dw_axi_dma_set_hw_desc(struct
 103         set_desc_src_master(hw_desc);
 104
 105         hw_desc->len = len;
 106 +
 107 +       if (burst_len && (chan->config.src_maxburst > burst_len))
 108 +               dev_warn_ratelimited(chan2dev(chan),
 109 +                                    "%s: requested source burst length %u exceeds supported burst length %u - data may be lost\n",
 110 +                                    axi_chan_name(chan), chan->config.src_maxburst, burst_len);
 111 +
 112         return 0;
 113  }
 114
 115 @@ -776,9 +791,6 @@ static size_t calculate_block_len(struct
 116         case DMA_MEM_TO_DEV:
 117                 data_width = BIT(chan->chip->dw->hdata->m_data_width);
 118                 mem_width = __ffs(data_width | dma_addr | buf_len);
 119 -               if (mem_width > DWAXIDMAC_TRANS_WIDTH_32)
 120 -                       mem_width = DWAXIDMAC_TRANS_WIDTH_32;
 121 -
 122                 block_len = axi_block_ts << mem_width;
 123                 break;
 124         case DMA_DEV_TO_MEM: