Implement setbrg in amlogic/meson serial device with driver model
similar to how the meson_uart.c driver does it in Linux. Also
configure (probe) the serial device with the new reg5 register.
Signed-off-by: Edoardo Tomelleri <[email protected]>
---
drivers/serial/serial_meson.c | 70 +++++++++++++++++++++++++++++++++++
include/configs/meson64.h | 7 ++++
2 files changed, 77 insertions(+)
diff --git a/drivers/serial/serial_meson.c b/drivers/serial/serial_meson.c
index d69ec221..90c370cf 100644
--- a/drivers/serial/serial_meson.c
+++ b/drivers/serial/serial_meson.c
@@ -7,9 +7,11 @@
#include <dm.h>
#include <errno.h>
#include <fdtdec.h>
+#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/compiler.h>
#include <serial.h>
+#include <clk.h>
struct meson_uart {
u32 wfifo;
@@ -17,6 +19,7 @@ struct meson_uart {
u32 control;
u32 status;
u32 misc;
+ u32 reg5; /* New baud control register */
};
struct meson_serial_plat {
@@ -42,6 +45,35 @@ struct meson_serial_plat {
#define AML_UART_RX_RST BIT(23)
#define AML_UART_CLR_ERR BIT(24)
+/* AML_UART_REG5 bits */
+#define AML_UART_REG5_XTAL_DIV2 BIT(27)
+#define AML_UART_REG5_XTAL_CLK_SEL BIT(26) /* default 0 (div by 3), 1 for
no div */
+#define AML_UART_REG5_USE_XTAL_CLK BIT(24) /* default 1 (use crystal as
clock source) */
+#define AML_UART_REG5_USE_NEW_BAUD BIT(23) /* default 1 (use new baud rate
register) */
+#define AML_UART_REG5_BAUD_MASK 0x7fffff
+
+static u32 meson_calc_baud_divisor(ulong src_rate, u32 baud)
+{
+ /*
+ * Usually src_rate is 24 MHz (from crystal) as clock source for serial
+ * device. Since 8 Mb/s is the maximum supported baud rate, use div by 3
+ * to derive baud rate. This choice is used also in meson_serial_setbrg.
+ */
+ return DIV_ROUND_CLOSEST(src_rate / 3, baud) - 1;
+}
+
+static void meson_serial_set_baud(struct meson_uart *uart, ulong src_rate, u32
baud)
+{
+ /*
+ * Set crystal divided by 3 (regardless of device tree clock property)
+ * as clock source and the corresponding divisor to approximate baud
+ */
+ u32 divisor = meson_calc_baud_divisor(src_rate, baud);
+ u32 val = AML_UART_REG5_USE_XTAL_CLK | AML_UART_REG5_USE_NEW_BAUD |
+ (divisor & AML_UART_REG5_BAUD_MASK);
+ writel(val, &uart->reg5);
+}
+
static void meson_serial_init(struct meson_uart *uart)
{
u32 val;
@@ -59,7 +91,14 @@ static int meson_serial_probe(struct udevice *dev)
{
struct meson_serial_plat *plat = dev_get_plat(dev);
struct meson_uart *const uart = plat->reg;
+ struct clk per_clk;
+ int ret = clk_get_by_name(dev, "baud", &per_clk);
+
+ if (ret)
+ return ret;
+ ulong rate = clk_get_rate(&per_clk);
+ meson_serial_set_baud(uart, rate, CONFIG_BAUDRATE);
meson_serial_init(uart);
return 0;
@@ -111,6 +150,36 @@ static int meson_serial_putc(struct udevice *dev, const
char ch)
return 0;
}
+static int meson_serial_setbrg(struct udevice *dev, const int baud)
+{
+ /*
+ * Change device baud rate if baud is reasonable (considering a 23 bit
+ * counter with an 8 MHz clock input) and the actual baud
+ * rate is within 2% of the requested value (2% is arbitrary).
+ */
+ if (baud < 1 || baud > 8000000)
+ return -EINVAL;
+
+ struct meson_serial_plat *const plat = dev_get_plat(dev);
+ struct meson_uart *const uart = plat->reg;
+ struct clk per_clk;
+ int ret = clk_get_by_name(dev, "baud", &per_clk);
+
+ if (ret)
+ return ret;
+ ulong rate = clk_get_rate(&per_clk);
+ u32 divisor = meson_calc_baud_divisor(rate, baud);
+ u32 calc_baud = (rate / 3) / (divisor + 1);
+ u32 calc_err = baud > calc_baud ? baud - calc_baud : calc_baud - baud;
+
+ if (((calc_err * 100) / baud) > 2)
+ return -EINVAL;
+
+ meson_serial_set_baud(uart, rate, baud);
+
+ return 0;
+}
+
static int meson_serial_pending(struct udevice *dev, bool input)
{
struct meson_serial_plat *plat = dev_get_plat(dev);
@@ -154,6 +223,7 @@ static const struct dm_serial_ops meson_serial_ops = {
.putc = meson_serial_putc,
.pending = meson_serial_pending,
.getc = meson_serial_getc,
+ .setbrg = meson_serial_setbrg,
};
static const struct udevice_id meson_serial_ids[] = {
diff --git a/include/configs/meson64.h b/include/configs/meson64.h
index 196e58ed..01413a02 100644
--- a/include/configs/meson64.h
+++ b/include/configs/meson64.h
@@ -16,6 +16,13 @@
#define GICC_BASE 0xc4302000
#endif
+/* Serial drivers */
+/* The following table includes the supported baudrates */
+#define CONFIG_SYS_BAUDRATE_TABLE \
+ {300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, \
+ 230400, 250000, 460800, 500000, 1000000, 2000000, 4000000, \
+ 8000000 }
+
/* For splashscreen */
#ifdef CONFIG_DM_VIDEO
#define STDOUT_CFG "vidconsole,serial"
