Alan, FYI: I am not using application, rather I have a Bluetooth driver invoking encode_baud_rate(...), please find log below. I made sure that c_ispeed = c_ospeed = 4.05M Baud, however I see tty_termios_encode_baud_rate(...) is normalizing to 4.0 manual trace log below: ====================================================================================== 4.05M Arbitrary Baud Setting Sequence: [ 9.664703] alloc_set_baud_rate_cmd Setting arbitrary baudrate using BOTHER baudrate:89 c_cflag:020000016262 [ 9.774658] XXXXXX_hci_uart_set_baudrate c_cflag:020000016262 baud:4050000 [ 9.781646] XXXXXX_hci_uart_set_baudrate arb flag set [ 9.786956] tty_termios_encode_baud_rate c_ispeed:4050000 c_ospeed:4050000 [ 9.794006] tty_termios_encode_baud_rate checking precise weird baudrate:0x80001cb2 [ 9.802032] tty_termios_encode_baud_rate checking precise weird baudrate c_cflag:020000006260 [ 9.810943] tty_termios_encode_baud_rate did we find close match? i:31 n_baud_table31 ifound:30 ofound:30 [ 9.820739] tty_termios_encode_baud_rate BOTHER, c_cflag:020000016277 [ 9.827209] tty_termios_baud_rate c_cflag:020000016277 cbaud:010017 [ 9.833648] tty_termios_baud_rate:(Arb'ry baud BOTHER not set) c_cflag:020000016277 cbaud:010017 [ 9.842773] tty_termios_baud_rate:cbaud:036 baud_val:4000000 [ 9.848480] tty_termios_baud_rate c_cflag:020000016277 cbaud:010017 [ 9.855499] tty_termios_baud_rate:(Arb'ry baud BOTHER not set) c_cflag:020000016277 cbaud:010017 [ 9.864471] tty_termios_baud_rate:cbaud:036 baud_val:4000000 [ 9.864501] pl011_set_termios baud:4000000 uart_clk:38400000 port:0 IBRD:1 FBRD:13 [ 10.674652] XXXXXX-uart XXXXXX-uart.0: Failed to set new baud rate (4) [ 10.681213] XXXXXX-uart XXXXXX-uart.0: Set chip power: DISABLE [ 10.692596] tty_termios_encode_baud_rate c_ispeed:0 c_ospeed:0 [ 10.698822] tty_termios_encode_baud_rate checking precise weird baudrate:0x80001cbf [ 10.706756] tty_termios_encode_baud_rate checking precise weird baudrate c_cflag:020000006260 [ 10.715698] tty_termios_encode_baud_rate did we find close match? i:31 n_baud_table31 ifound:0 ofound:0 [ 10.725769] tty_termios_encode_baud_rate BOTHER, c_cflag:020000006260 [ 10.732574] tty_termios_baud_rate c_cflag:020000006260 cbaud:00 [ 10.739929] tty_termios_baud_rate:(Arb'ry baud BOTHER not set) c_cflag:020000006260 cbaud:00 [ 10.749176] tty_termios_baud_rate:cbaud:00 baud_val:0 [ 10.754638] tty_termios_baud_rate c_cflag:020000006260 cbaud:00 [ 10.761505] tty_termios_baud_rate:(Arb'ry baud BOTHER not set) c_cflag:020000006260 cbaud:00 [ 10.770660] tty_termios_baud_rate:cbaud:00 baud_val:0 4.05 is failing: alloc_set_baud_rate_cmd Setting arbitrary baudrate using BOTHER baudrate:89 c_cflag:020000016262 [ 9.325225] av8100_hdmi av8100_hdmi.3: HDMI display probed [ 9.334686] XXXXXX_hci_uart_set_baudrate c_cflag:020000016262 baud:4050000, ispeed:4050000 ospeed:4050000 [ 9.345275] tty_termios_encode_baud_rate c_ispeed:4050000 c_ospeed:4050000 [ 9.352539] tty_termios_encode_baud_rate checking precise weird baudrate:0x80001cb2 [ 9.360717] tty_termios_encode_baud_rate checking precise weird baudrate c_cflag:020000006260 [ 9.369659] tty_termios_encode_baud_rate did we find close match? i:31 n_baud_table31 ifound:30 ofound:30 [ 9.380035] tty_termios_encode_baud_rate BOTHER, c_cflag:020000016277 [ 9.387237] tty_termios_baud_rate c_cflag:020000016277 cbaud:010017 [ 9.393829] pl011_set_termios i_speed:4050000 o_speed:4050000 [ 9.399993] tty_termios_baud_rate c_cflag:020000016277 cbaud:010017 4.8M Arbitrary BaudSetting Sequence: [ 10.004699] alloc_set_baud_rate_cmd Setting arbitrary baudrate using BOTHER baudrate:90 c_cflag:020000016262 [ 10.114624] XXXXXX_hci_uart_set_baudrate c_cflag:020000016262 baud:4800000 [ 10.122009] XXXXXX_hci_uart_set_baudrate arb flag set [ 10.127624] tty_termios_encode_baud_rate c_ispeed:4800000 c_ospeed:4800000 [ 10.134887] tty_termios_encode_baud_rate checking precise weird baudrate:0x80001cb2 [ 10.143218] tty_termios_encode_baud_rate checking precise weird baudrate c_cflag:020000006260 [ 10.154113] tty_termios_encode_baud_rate did we find close match? i:31 n_baud_table31 ifound:-1 ofound:-1 [ 10.172149] tty_termios_encode_baud_rate BOTHER, c_cflag:020000016260 [ 10.178833] tty_termios_baud_rate c_cflag:020000016260 cbaud:010000 [ 10.185424] tty_termios_baud_rate (Arb'ry baud set) c_cflag:020000016260 cbaud:010000 [ 10.193572] i_speed:4800000 o_speed:4800000 [ 10.197845] tty_termios_baud_rate c_cflag:020000016260 cbaud:010000 [ 10.204620] tty_termios_baud_rate (Arb'ry baud set) c_cflag:020000016260 cbaud:010000 [ 10.212799] pl011_set_termios baud:4800000 uart_clk:38400000 port:0 IBRD:1 FBRD:0 [ 10.220764] XXXXXX-uart XXXXXX-uart.0: Baud rate changed to 4800000 baud [ 10.973632] Bluetooth: XXXXXX BT core is enabled [ 11.101867] Bluetooth: XXXXXX BT core is disabled ====================================================================================== Thanks, Rajanikanth -----Original Message----- From: Alan Cox [mailto:alan@xxxxxxxxxxxxxxxxxxx] Sent: Thursday, January 12, 2012 5:19 PM To: Rajanikanth H V Cc: linux-serial@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; gregkh@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Subject: Re: tty/serial: Need clarification on Support for 4+M Baudrate On Thu, 12 Jan 2012 10:49:38 +0100 Rajanikanth H V <rajanikanth.hv@xxxxxxxxxxxxxx> wrote: > Alan, > > Thanks for your response, suggested modification helped to get 4.8M baud > but not 4.05M as this is being approximated to 4.0M baud which happens in > tty_termios_encode_baud_rate(...). Only if you don't have the BOTHER flag set and only for returned data to user space. When you do a TCSETS2 ioctl and have BOTHER set as the rate as well as a c_ispeed/c_ospeed the exactly value is given to the driver. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
