| Message ID | 1374691051-28544-4-git-send-email-sboyd@codeaurora.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Wed, Jul 24, 2013 at 11:37:30AM -0700, Stephen Boyd wrote: >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(-) Acked-by: David Brown <davidb@codeaurora.org>
On Wed, Jul 24, 2013 at 10:37 AM, Stephen Boyd <sboyd@codeaurora.org> wrote: > [snip] > + 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 */ Shouldn't matter, but you're not defaulting to the smallest divider. Your are defaulting to an undefined value, as `entry` will be off the array once i == ARRAY_SIZE(). Regards, Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 07/25, Bjorn Andersson wrote: > On Wed, Jul 24, 2013 at 10:37 AM, Stephen Boyd <sboyd@codeaurora.org> wrote: > > [snip] > > + 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 */ > > Shouldn't matter, but you're not defaulting to the smallest divider. > Your are defaulting to an undefined value, as `entry` will be off the > array once i == ARRAY_SIZE(). > Yes because the if condition will always be true. Perhaps that's too confusing? We could add a subtraction by 1 to make it more obvious. for (i = 0; entry = table; i < ARRAY_SIZE(table) - 1; i++, entry++) if (entry->divisor <= divisor) break; return entry; /* Default to smallest divider*/
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); }
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(-)