serial: mtk: add support for using dynamic baud clock souce

The baud clock on some platform may change due to assigned-clock-parent
set in DT. In current flow the baud clock is only retrieved during probe
stage. If the parent of the source clock changes after probe stage, the
setbrg will set wrong baudrate.

To get the right clock rate, this patch records the baud clk struct to the
driver's priv, and changes the driver's flow to get the clock rate before
calling _mtk_serial_setbrg().

Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>

diff --git a/drivers/serial/serial_mtk.c b/drivers/serial/serial_mtk.c
index 22251c5f4ce4f8828ed06a80a5802a04e0107970..03b9e86bfc209598c741b53674f0b5360ae2f0af 100644 (file)
--- a/drivers/serial/serial_mtk.c
+++ b/drivers/serial/serial_mtk.c
@@ -10,6 +10,7 @@
 #include <common.h>
 #include <div64.h>
 #include <dm.h>
+#include <dm/device_compat.h>
 #include <errno.h>
 #include <log.h>
 #include <serial.h>
@@ -70,27 +71,37 @@ struct mtk_serial_regs {
 #define BAUD_ALLOW_MAX(baud)   ((baud) + (baud) * 3 / 100)
 #define BAUD_ALLOW_MIX(baud)   ((baud) - (baud) * 3 / 100)
 
+/* struct mtk_serial_priv -    Structure holding all information used by the
+ *                             driver
+ * @regs:                      Register base of the serial port
+ * @clk:                       The baud clock device
+ * @fixed_clk_rate:            Fallback fixed baud clock rate if baud clock
+ *                             device is not specified
+ * @force_highspeed:           Force using high-speed mode
+ */
 struct mtk_serial_priv {
        struct mtk_serial_regs __iomem *regs;
-       u32 clock;
+       struct clk clk;
+       u32 fixed_clk_rate;
        bool force_highspeed;
 };
 
-static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
+static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud,
+                              uint clk_rate)
 {
        u32 quot, realbaud, samplecount = 1;
 
        /* Special case for low baud clock */
-       if (baud <= 115200 && priv->clock <= 12000000) {
+       if (baud <= 115200 && clk_rate == 12000000) {
                writel(3, &priv->regs->highspeed);
 
-               quot = DIV_ROUND_CLOSEST(priv->clock, 256 * baud);
+               quot = DIV_ROUND_CLOSEST(clk_rate, 256 * baud);
                if (quot == 0)
                        quot = 1;
 
-               samplecount = DIV_ROUND_CLOSEST(priv->clock, quot * baud);
+               samplecount = DIV_ROUND_CLOSEST(clk_rate, quot * baud);
 
-               realbaud = priv->clock / samplecount / quot;
+               realbaud = clk_rate / samplecount / quot;
                if (realbaud > BAUD_ALLOW_MAX(baud) ||
                    realbaud < BAUD_ALLOW_MIX(baud)) {
                        pr_info("baud %d can't be handled\n", baud);
@@ -104,7 +115,7 @@ static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
 
        if (baud <= 115200) {
                writel(0, &priv->regs->highspeed);
-               quot = DIV_ROUND_CLOSEST(priv->clock, 16 * baud);
+               quot = DIV_ROUND_CLOSEST(clk_rate, 16 * baud);
        } else if (baud <= 576000) {
                writel(2, &priv->regs->highspeed);
 
@@ -112,13 +123,13 @@ static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud)
                if ((baud == 500000) || (baud == 576000))
                        baud = 460800;
 
-               quot = DIV_ROUND_UP(priv->clock, 4 * baud);
+               quot = DIV_ROUND_UP(clk_rate, 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);
+               quot = DIV_ROUND_UP(clk_rate, 256 * baud);
+               samplecount = DIV_ROUND_CLOSEST(clk_rate, quot * baud);
        }
 
 set_baud:
@@ -167,8 +178,13 @@ static int _mtk_serial_pending(struct mtk_serial_priv *priv, bool input)
 static int mtk_serial_setbrg(struct udevice *dev, int baudrate)
 {
        struct mtk_serial_priv *priv = dev_get_priv(dev);
+       u32 clk_rate;
+
+       clk_rate = clk_get_rate(&priv->clk);
+       if (IS_ERR_VALUE(clk_rate) || clk_rate == 0)
+               clk_rate = priv->fixed_clk_rate;
 
-       _mtk_serial_setbrg(priv, baudrate);
+       _mtk_serial_setbrg(priv, baudrate, clk_rate);
 
        return 0;
 }
@@ -211,7 +227,6 @@ static int mtk_serial_of_to_plat(struct udevice *dev)
 {
        struct mtk_serial_priv *priv = dev_get_priv(dev);
        fdt_addr_t addr;
-       struct clk clk;
        int err;
 
        addr = dev_read_addr(dev);
@@ -220,22 +235,19 @@ static int mtk_serial_of_to_plat(struct udevice *dev)
 
        priv->regs = map_physmem(addr, 0, MAP_NOCACHE);
 
-       err = clk_get_by_index(dev, 0, &clk);
-       if (!err) {
-               err = clk_get_rate(&clk);
-               if (!IS_ERR_VALUE(err))
-                       priv->clock = err;
-       } else if (err != -ENOENT && err != -ENODEV && err != -ENOSYS) {
-               debug("mtk_serial: failed to get clock\n");
-               return err;
-       }
-
-       if (!priv->clock)
-               priv->clock = dev_read_u32_default(dev, "clock-frequency", 0);
-
-       if (!priv->clock) {
-               debug("mtk_serial: clock not defined\n");
-               return -EINVAL;
+       err = clk_get_by_index(dev, 0, &priv->clk);
+       if (err) {
+               err = dev_read_u32(dev, "clock-frequency", &priv->fixed_clk_rate);
+               if (err) {
+                       dev_err(dev, "baud clock not defined\n");
+                       return -EINVAL;
+               }
+       } else {
+               err = clk_get_rate(&priv->clk);
+               if (IS_ERR_VALUE(err)) {
+                       dev_err(dev, "invalid baud clock\n");
+                       return -EINVAL;
+               }
        }
 
        priv->force_highspeed = dev_read_bool(dev, "mediatek,force-highspeed");
@@ -273,7 +285,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #define DECLARE_HSUART_PRIV(port) \
        static struct mtk_serial_priv mtk_hsuart##port = { \
        .regs = (struct mtk_serial_regs *)CONFIG_SYS_NS16550_COM##port, \
-       .clock = CONFIG_SYS_NS16550_CLK \
+       .fixed_clk_rate = CONFIG_SYS_NS16550_CLK \
 };
 
 #define DECLARE_HSUART_FUNCTIONS(port) \
@@ -282,12 +294,14 @@ DECLARE_GLOBAL_DATA_PTR;
                writel(0, &mtk_hsuart##port.regs->ier); \
                writel(UART_MCRVAL, &mtk_hsuart##port.regs->mcr); \
                writel(UART_FCRVAL, &mtk_hsuart##port.regs->fcr); \
-               _mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate); \
+               _mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
+                                  mtk_hsuart##port.fixed_clk_rate); \
                return 0 ; \
        } \
        static void mtk_serial##port##_setbrg(void) \
        { \
-               _mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate); \
+               _mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
+                                  mtk_hsuart##port.fixed_clk_rate); \
        } \
        static int mtk_serial##port##_getc(void) \
        { \
@@ -427,13 +441,13 @@ static inline void _debug_uart_init(void)
        struct mtk_serial_priv priv;
 
        priv.regs = (void *) CONFIG_VAL(DEBUG_UART_BASE);
-       priv.clock = CONFIG_DEBUG_UART_CLOCK;
+       priv.fixed_clk_rate = CONFIG_DEBUG_UART_CLOCK;
 
        writel(0, &priv.regs->ier);
        writel(UART_MCRVAL, &priv.regs->mcr);
        writel(UART_FCRVAL, &priv.regs->fcr);
 
-       _mtk_serial_setbrg(&priv, CONFIG_BAUDRATE);
+       _mtk_serial_setbrg(&priv, CONFIG_BAUDRATE, priv.fixed_clk_rate);
 }
 
 static inline void _debug_uart_putc(int ch)