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Subject[PATCH 3/4] msm_serial: Make baud_code detection more dynamic
Date
Currently msm_set_baud_rate() assumes the uart clock rate is
1.8432 MHz. This is not always true, and limits our options to
program the baud rate. Instead of assuming the rate and
hard-coding the baud_code based on it, calculate the divider that
we want and try to find the closest baud_code that matches. This
allows us to support uarts with faster clock speeds.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
drivers/tty/serial/msm_serial.c | 98 ++++++++++++++++++-----------------------
drivers/tty/serial/msm_serial.h | 18 ++------
2 files changed, 48 insertions(+), 68 deletions(-)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index cab4105..cef8f40 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -322,70 +322,60 @@ static void msm_break_ctl(struct uart_port *port, int break_ctl)
msm_write(port, UART_CR_CMD_STOP_BREAK, UART_CR);
}

+struct msm_baud_map {
+ u16 divisor;
+ u8 code;
+ u8 rxstale;
+};
+
+static const struct msm_baud_map *
+msm_find_best_baud(struct uart_port *port, unsigned int baud)
+{
+ unsigned int i, divisor;
+ const struct msm_baud_map *entry;
+ static const struct msm_baud_map table[] = {
+ { 1536, 0x00, 1 },
+ { 768, 0x11, 1 },
+ { 384, 0x22, 1 },
+ { 192, 0x33, 1 },
+ { 96, 0x44, 1 },
+ { 48, 0x55, 1 },
+ { 32, 0x66, 1 },
+ { 24, 0x77, 1 },
+ { 16, 0x88, 1 },
+ { 12, 0x99, 6 },
+ { 8, 0xaa, 6 },
+ { 6, 0xbb, 6 },
+ { 4, 0xcc, 6 },
+ { 3, 0xdd, 8 },
+ { 2, 0xee, 16 },
+ { 1, 0xff, 31 },
+ };
+
+ divisor = uart_get_divisor(port, baud);
+
+ for (i = 0, entry = table; i < ARRAY_SIZE(table); i++, entry++)
+ if (entry->divisor <= divisor)
+ break;
+
+ return entry; /* Default to smallest divider */
+}
+
static int msm_set_baud_rate(struct uart_port *port, unsigned int baud)
{
- unsigned int baud_code, rxstale, watermark;
+ unsigned int rxstale, watermark;
struct msm_port *msm_port = UART_TO_MSM(port);
+ const struct msm_baud_map *entry;

- switch (baud) {
- case 300:
- baud_code = UART_CSR_300;
- rxstale = 1;
- break;
- case 600:
- baud_code = UART_CSR_600;
- rxstale = 1;
- break;
- case 1200:
- baud_code = UART_CSR_1200;
- rxstale = 1;
- break;
- case 2400:
- baud_code = UART_CSR_2400;
- rxstale = 1;
- break;
- case 4800:
- baud_code = UART_CSR_4800;
- rxstale = 1;
- break;
- case 9600:
- baud_code = UART_CSR_9600;
- rxstale = 2;
- break;
- case 14400:
- baud_code = UART_CSR_14400;
- rxstale = 3;
- break;
- case 19200:
- baud_code = UART_CSR_19200;
- rxstale = 4;
- break;
- case 28800:
- baud_code = UART_CSR_28800;
- rxstale = 6;
- break;
- case 38400:
- baud_code = UART_CSR_38400;
- rxstale = 8;
- break;
- case 57600:
- baud_code = UART_CSR_57600;
- rxstale = 16;
- break;
- case 115200:
- default:
- baud_code = UART_CSR_115200;
- baud = 115200;
- rxstale = 31;
- break;
- }
+ entry = msm_find_best_baud(port, baud);

if (msm_port->is_uartdm)
msm_write(port, UART_CR_CMD_RESET_RX, UART_CR);

- msm_write(port, baud_code, UART_CSR);
+ msm_write(port, entry->code, UART_CSR);

/* RX stale watermark */
+ rxstale = entry->rxstale;
watermark = UART_IPR_STALE_LSB & rxstale;
watermark |= UART_IPR_RXSTALE_LAST;
watermark |= UART_IPR_STALE_TIMEOUT_MSB & (rxstale << 2);
diff --git a/drivers/tty/serial/msm_serial.h b/drivers/tty/serial/msm_serial.h
index 15c186e..469fda5 100644
--- a/drivers/tty/serial/msm_serial.h
+++ b/drivers/tty/serial/msm_serial.h
@@ -38,19 +38,7 @@
#define UART_MR2_PARITY_MODE_SPACE 0x3
#define UART_MR2_PARITY_MODE 0x3

-#define UART_CSR 0x0008
-#define UART_CSR_115200 0xFF
-#define UART_CSR_57600 0xEE
-#define UART_CSR_38400 0xDD
-#define UART_CSR_28800 0xCC
-#define UART_CSR_19200 0xBB
-#define UART_CSR_14400 0xAA
-#define UART_CSR_9600 0x99
-#define UART_CSR_4800 0x77
-#define UART_CSR_2400 0x55
-#define UART_CSR_1200 0x44
-#define UART_CSR_600 0x33
-#define UART_CSR_300 0x22
+#define UART_CSR 0x0008

#define UART_TF 0x000C
#define UARTDM_TF 0x0070
@@ -152,6 +140,7 @@ static inline void msm_serial_set_mnd_regs_tcxo(struct uart_port *port)
msm_write(port, 0xF1, UART_NREG);
msm_write(port, 0x0F, UART_DREG);
msm_write(port, 0x1A, UART_MNDREG);
+ port->uartclk = 1843200;
}

/*
@@ -163,6 +152,7 @@ static inline void msm_serial_set_mnd_regs_tcxoby4(struct uart_port *port)
msm_write(port, 0xF6, UART_NREG);
msm_write(port, 0x0F, UART_DREG);
msm_write(port, 0x0A, UART_MNDREG);
+ port->uartclk = 1843200;
}

static inline
@@ -170,7 +160,7 @@ void msm_serial_set_mnd_regs_from_uartclk(struct uart_port *port)
{
if (port->uartclk == 19200000)
msm_serial_set_mnd_regs_tcxo(port);
- else
+ else if (port->uartclk == 4800000)
msm_serial_set_mnd_regs_tcxoby4(port);
}

--
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