package/boot/uboot-mediatek/patches/000-mtk-11-serial-serial-mtk-rewrite-the-setbrg-function.patch

   1 From d8bde59186dafdea5bbe8d29d3a6ae7cac98e9d0 Mon Sep 17 00:00:00 2001
   2 From: Weijie Gao <weijie.gao@mediatek.com>
   3 Date: Mon, 25 Jan 2021 11:19:08 +0800
   4 Subject: [PATCH 11/21] serial: serial-mtk: rewrite the setbrg function
   5
   6 Currently the setbrg logic of serial-mtk is messy, and should be rewritten.
   7 Also an option is added to make it possible to use highspeed=3 mode for all
   8 bauds.
   9
  10 The new logic is:
  11 1. If baud clock > 12MHz
  12    a) If baud <= 115200, highspeed=0 mode will be used (ns16550 compatible)
  13    b) If baud <= 576000, highspeed=2 mode will be used
  14    c) any baud > 576000, highspeed=3 mode will be used
  15 2. If baud clock <= 12MHz
  16    Always uses highspeed=3 mode
  17    a) If baud <= 115200, calculates the divisor using DIV_ROUND_CLOSEST
  18    b) any baud > 115200, the same as 1. c)
  19
  20 Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
  21 ---
  22  drivers/serial/serial_mtk.c | 74 +++++++++++++++++--------------------
  23  1 file changed, 33 insertions(+), 41 deletions(-)
  24
  25 --- a/drivers/serial/serial_mtk.c
  26 +++ b/drivers/serial/serial_mtk.c
  27 @@ -73,74 +73,64 @@ struct mtk_serial_regs {
  28  struct mtk_serial_priv {
  29         struct mtk_serial_regs __iomem *regs;
  30         u32 clock;
  31 +       bool force_highspeed;
  32  };
  33
  34  static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
  35  {
  36 -       bool support_clk12m_baud115200;
  37 -       u32 quot, samplecount, realbaud;
  38 +       u32 quot, realbaud, samplecount = 1;
  39
  40 -       if ((baud <= 115200) && (priv->clock == 12000000))
  41 -               support_clk12m_baud115200 = true;
  42 -       else
  43 -               support_clk12m_baud115200 = false;
  44 +       /* Special case for low baud clock */
  45 +       if ((baud <= 115200) && (priv->clock == 12000000)) {
  46 +               writel(3, &priv->regs->highspeed);
  47 +
  48 +               quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
  49 +               if (quot == 0)
  50 +                       quot = 1;
  51 +
  52 +               samplecount = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
  53 +
  54 +               realbaud = priv->clock / samplecount / quot;
  55 +               if ((realbaud > BAUD_ALLOW_MAX(baud)) ||
  56 +                   (realbaud < BAUD_ALLOW_MIX(baud))) {
  57 +                       pr_info("baud %d can't be handled\n", baud);
  58 +               }
  59 +
  60 +               goto set_baud;
  61 +       }
  62 +
  63 +       if (priv->force_highspeed)
  64 +               goto use_hs3;
  65
  66         if (baud <= 115200) {
  67                 writel(0, &priv->regs->highspeed);
  68                 quot = DIV_ROUND_CLOSEST(priv->clock, 16 * baud);
  69 -
  70 -               if (support_clk12m_baud115200) {
  71 -                       writel(3, &priv->regs->highspeed);
  72 -                       quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
  73 -                       if (quot == 0)
  74 -                               quot = 1;
  75 -
  76 -                       samplecount = DIV_ROUND_CLOSEST(priv->clock,
  77 -                                                       quot * baud);
  78 -                       if (samplecount != 0) {
  79 -                               realbaud = priv->clock / samplecount / quot;
  80 -                               if ((realbaud > BAUD_ALLOW_MAX(baud)) ||
  81 -                                   (realbaud < BAUD_ALLOW_MIX(baud))) {
  82 -                                       pr_info("baud %d can't be handled\n",
  83 -                                               baud);
  84 -                               }
  85 -                       } else {
  86 -                               pr_info("samplecount is 0\n");
  87 -                       }
  88 -               }
  89         } else if (baud <= 576000) {
  90                 writel(2, &priv->regs->highspeed);
  91
  92                 /* Set to next lower baudrate supported */
  93                 if ((baud == 500000) || (baud == 576000))
  94                         baud = 460800;
  95 +
  96                 quot = DIV_ROUND_UP(priv->clock, 4 * baud);
  97         } else {
  98 +use_hs3:
  99                 writel(3, &priv->regs->highspeed);
 100 +
 101                 quot = DIV_ROUND_UP(priv->clock, 256 * baud);
 102 +               samplecount = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
 103         }
 104
 105 +set_baud:
 106         /* set divisor */
 107         writel(UART_LCR_WLS_8 | UART_LCR_DLAB, &priv->regs->lcr);
 108         writel(quot & 0xff, &priv->regs->dll);
 109         writel((quot >> 8) & 0xff, &priv->regs->dlm);
 110         writel(UART_LCR_WLS_8, &priv->regs->lcr);
 111
 112 -       if (baud > 460800) {
 113 -               u32 tmp;
 114 -
 115 -               tmp = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
 116 -               writel(tmp - 1, &priv->regs->sample_count);
 117 -               writel((tmp - 2) >> 1, &priv->regs->sample_point);
 118 -       } else {
 119 -               writel(0, &priv->regs->sample_count);
 120 -               writel(0xff, &priv->regs->sample_point);
 121 -       }
 122 -
 123 -       if (support_clk12m_baud115200) {
 124 -               writel(samplecount - 1, &priv->regs->sample_count);
 125 -               writel((samplecount - 2) >> 1, &priv->regs->sample_point);
 126 -       }
 127 +       /* set highspeed mode sample count & point */
 128 +       writel(samplecount - 1, &priv->regs->sample_count);
 129 +       writel((samplecount - 2) >> 1, &priv->regs->sample_point);
 130  }
 131
 132  static int _mtk_serial_putc(struct mtk_serial_priv *priv, const char ch)
 133 @@ -248,6 +238,8 @@ static int mtk_serial_of_to_plat(struct
 134                 return -EINVAL;
 135         }
 136
 137 +       priv->force_highspeed = dev_read_bool(dev, "mediatek,force-highspeed");
 138 +
 139         return 0;
 140  }
 141