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serial: mtk: rewrite the setbrg function

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Currently the setbrg logic of serial-mtk is messy, and should be rewritten.
Also an option is added to make it possible to use highspeed-3 mode for all
bauds.

The new logic is:
1. If baud clock > 12MHz
   a) If baud <= 115200, highspeed-0 mode will be used (ns16550 compatible)
   b) If baud <= 576000, highspeed-2 mode will be used
   c) any bauds > 576000, highspeed-3 mode will be used
2. If baud clock <= 12MHz
   Forced highspeed-3 mode
   a) If baud <= 115200, calculates the divisor using DIV_ROUND_CLOSEST
   b) any bauds > 115200, the same as 1. c)

Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
This commit is contained in:
Weijie Gao 2021-03-05 10:35:39 +08:00 committed by Tom Rini
parent e8b98f0270
commit 0b9f1ae586
1 changed files with 33 additions and 41 deletions
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74
drivers/serial/serial_mtk.c
View file

@ -73,74 +73,64 @@ struct mtk_serial_regs {
struct mtk_serial_priv {
struct mtk_serial_regs __iomem *regs;
u32 clock;
bool force_highspeed;
};
static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
{
bool support_clk12m_baud115200;
u32 quot, samplecount, realbaud;
u32 quot, realbaud, samplecount = 1;
if ((baud <= 115200) && (priv->clock == 12000000))
support_clk12m_baud115200 = true;
else
support_clk12m_baud115200 = false;
/* Special case for low baud clock */
if (baud <= 115200 && priv->clock <= 12000000) {
writel(3, &priv->regs->highspeed);
quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
if (quot == 0)
quot = 1;
samplecount = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
realbaud = priv->clock / samplecount / quot;
if (realbaud > BAUD_ALLOW_MAX(baud) ||
realbaud < BAUD_ALLOW_MIX(baud)) {
pr_info("baud %d can't be handled\n", baud);
}
goto set_baud;
}
if (priv->force_highspeed)
goto use_hs3;
if (baud <= 115200) {
writel(0, &priv->regs->highspeed);
quot = DIV_ROUND_CLOSEST(priv->clock, 16 * baud);
if (support_clk12m_baud115200) {
writel(3, &priv->regs->highspeed);
quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
if (quot == 0)
quot = 1;
samplecount = DIV_ROUND_CLOSEST(priv->clock,
quot * baud);
if (samplecount != 0) {
realbaud = priv->clock / samplecount / quot;
if ((realbaud > BAUD_ALLOW_MAX(baud)) ||
(realbaud < BAUD_ALLOW_MIX(baud))) {
pr_info("baud %d can't be handled\n",
baud);
}
} else {
pr_info("samplecount is 0\n");
}
}
} else if (baud <= 576000) {
writel(2, &priv->regs->highspeed);
/* Set to next lower baudrate supported */
if ((baud == 500000) || (baud == 576000))
baud = 460800;
quot = DIV_ROUND_UP(priv->clock, 4 * baud);
} else {
use_hs3:
writel(3, &priv->regs->highspeed);
quot = DIV_ROUND_UP(priv->clock, 256 * baud);
samplecount = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
}
set_baud:
/* set divisor */
writel(UART_LCR_WLS_8 | UART_LCR_DLAB, &priv->regs->lcr);
writel(quot & 0xff, &priv->regs->dll);
writel((quot >> 8) & 0xff, &priv->regs->dlm);
writel(UART_LCR_WLS_8, &priv->regs->lcr);
if (baud > 460800) {
u32 tmp;
tmp = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
writel(tmp - 1, &priv->regs->sample_count);
writel((tmp - 2) >> 1, &priv->regs->sample_point);
} else {
writel(0, &priv->regs->sample_count);
writel(0xff, &priv->regs->sample_point);
}
if (support_clk12m_baud115200) {
writel(samplecount - 1, &priv->regs->sample_count);
writel((samplecount - 2) >> 1, &priv->regs->sample_point);
}
/* set highspeed mode sample count & point */
writel(samplecount - 1, &priv->regs->sample_count);
writel((samplecount - 2) >> 1, &priv->regs->sample_point);
}
static int _mtk_serial_putc(struct mtk_serial_priv *priv, const char ch)
@ -248,6 +238,8 @@ static int mtk_serial_of_to_plat(struct udevice *dev)
return -EINVAL;
}
priv->force_highspeed = dev_read_bool(dev, "mediatek,force-highspeed");
return 0;
}