* Re: tty: uart: custom speed [not found] ` <20190304132302.GA9869@kroah.com> @ 2019-03-04 14:49 ` Subhashini Rao Beerisetty 2019-03-04 14:57 ` Greg KH 0 siblings, 1 reply; 6+ messages in thread From: Subhashini Rao Beerisetty @ 2019-03-04 14:49 UTC (permalink / raw) To: Greg KH; +Cc: linux-serial, kernelnewbies On Mon, Mar 4, 2019 at 6:53 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Mon, Mar 04, 2019 at 05:46:54PM +0530, Subhashini Rao Beerisetty wrote: > > Hi All, > > > > > > I’ve an UART ports on Xilinx FPGA board and it gets connected to PC > > via PCIe bus. I could not find any kernel serial driver which supports > > our hardware so I plan to develop a new driver. I see two approaches > > to develop an UART driver i.e. either by using tty_register_driver() > > or an uart_register_driver(). > > > > > > Regarding my UART module, it has a counter of 16 bits and runs on a > > 32Mhz clock. It supports all the standard & non-standard baud’s up to > > 4Mbps. > > What type of UART is it? Odds are it is based on an existing design, no > one creates a brand-new UART anymore. Hopefully. If not, what a > waste... For UART type, I see the permitted types are none, 8250, 16450, 16550, 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. Looking into the data sheet I haven’t found any register or parameter defining any of those UART types. Is ‘UART type’ is determined from a register settings point of view or a pinout point of view? > > > If I used struct tty_operations, I noticed that baud rate changing is > > done via “.set_termios” API, but this method only supports standard > > baud rates. I’d like to know why this API does not support > > non-standard baud rates? > > Why do you think it does not? From data sheet point of view I'm clear on how to set the non-standard baud rate, even I exposed a custom Ioctl for this. But here I’m trying to understand how it is achieved by using available UART kernel framework. For non-standard baud rate requests, observed that tty->termios.c_ispeed & tty->termios.c_ospeed set to 38400. I did not understood why it changes? > > Anyway, use the uart interface as odds are your uart is already > supported. Get the data sheet and start reading :) > > good luck, > > greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: tty: uart: custom speed 2019-03-04 14:49 ` tty: uart: custom speed Subhashini Rao Beerisetty @ 2019-03-04 14:57 ` Greg KH 2019-03-04 15:23 ` Subhashini Rao Beerisetty 0 siblings, 1 reply; 6+ messages in thread From: Greg KH @ 2019-03-04 14:57 UTC (permalink / raw) To: Subhashini Rao Beerisetty; +Cc: linux-serial, kernelnewbies On Mon, Mar 04, 2019 at 08:19:44PM +0530, Subhashini Rao Beerisetty wrote: > On Mon, Mar 4, 2019 at 6:53 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > On Mon, Mar 04, 2019 at 05:46:54PM +0530, Subhashini Rao Beerisetty wrote: > > > Hi All, > > > > > > > > > I’ve an UART ports on Xilinx FPGA board and it gets connected to PC > > > via PCIe bus. I could not find any kernel serial driver which supports > > > our hardware so I plan to develop a new driver. I see two approaches > > > to develop an UART driver i.e. either by using tty_register_driver() > > > or an uart_register_driver(). > > > > > > > > > Regarding my UART module, it has a counter of 16 bits and runs on a > > > 32Mhz clock. It supports all the standard & non-standard baud’s up to > > > 4Mbps. > > > > What type of UART is it? Odds are it is based on an existing design, no > > one creates a brand-new UART anymore. Hopefully. If not, what a > > waste... > > For UART type, I see the permitted types are none, 8250, 16450, 16550, > 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. > Looking into the data sheet I haven’t found any register or parameter > defining any of those UART types. Is ‘UART type’ is determined from a > register settings point of view or a pinout point of view? register settings point of view. I suggest you do some basic research into how UARTs work before continuing with this effort, it will save you a lot of time in the end :) > > > If I used struct tty_operations, I noticed that baud rate changing is > > > done via “.set_termios” API, but this method only supports standard > > > baud rates. I’d like to know why this API does not support > > > non-standard baud rates? > > > > Why do you think it does not? > From data sheet point of view I'm clear on how to set the non-standard > baud rate, even I exposed a custom Ioctl for this. But here I’m trying > to understand how it is achieved by using available UART kernel > framework. > For non-standard baud rate requests, observed that > tty->termios.c_ispeed & tty->termios.c_ospeed set to 38400. I did not > understood why it changes? Have you read the documentation on how to set custom baud rates? I can't find the link to it at the moment, but it is very possible to do that today, no special ioctls are needed at all. I think someone was finally working on getting glibc to support it directly, but I do not know if those patches ever got merged, so you would just have to "open code" it in userspace if you want to do this. good luck! greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: tty: uart: custom speed 2019-03-04 14:57 ` Greg KH @ 2019-03-04 15:23 ` Subhashini Rao Beerisetty 2019-03-04 17:16 ` Vladimir Zapolskiy 2019-03-04 18:47 ` Grant Edwards 0 siblings, 2 replies; 6+ messages in thread From: Subhashini Rao Beerisetty @ 2019-03-04 15:23 UTC (permalink / raw) To: Greg KH; +Cc: linux-serial, kernelnewbies On Mon, Mar 4, 2019 at 8:27 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Mon, Mar 04, 2019 at 08:19:44PM +0530, Subhashini Rao Beerisetty wrote: > > On Mon, Mar 4, 2019 at 6:53 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > > > On Mon, Mar 04, 2019 at 05:46:54PM +0530, Subhashini Rao Beerisetty wrote: > > > > Hi All, > > > > > > > > > > > > I’ve an UART ports on Xilinx FPGA board and it gets connected to PC > > > > via PCIe bus. I could not find any kernel serial driver which supports > > > > our hardware so I plan to develop a new driver. I see two approaches > > > > to develop an UART driver i.e. either by using tty_register_driver() > > > > or an uart_register_driver(). > > > > > > > > > > > > Regarding my UART module, it has a counter of 16 bits and runs on a > > > > 32Mhz clock. It supports all the standard & non-standard baud’s up to > > > > 4Mbps. > > > > > > What type of UART is it? Odds are it is based on an existing design, no > > > one creates a brand-new UART anymore. Hopefully. If not, what a > > > waste... > > > > For UART type, I see the permitted types are none, 8250, 16450, 16550, > > 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. > > Looking into the data sheet I haven’t found any register or parameter > > defining any of those UART types. Is ‘UART type’ is determined from a > > register settings point of view or a pinout point of view? > > register settings point of view. > > I suggest you do some basic research into how UARTs work before > continuing with this effort, it will save you a lot of time in the end > :) Thanks for you suggestion. I will study on this, I’m glad if you can point some good documentation links on this. > > > > > If I used struct tty_operations, I noticed that baud rate changing is > > > > done via “.set_termios” API, but this method only supports standard > > > > baud rates. I’d like to know why this API does not support > > > > non-standard baud rates? > > > > > > Why do you think it does not? > > From data sheet point of view I'm clear on how to set the non-standard > > baud rate, even I exposed a custom Ioctl for this. But here I’m trying > > to understand how it is achieved by using available UART kernel > > framework. > > For non-standard baud rate requests, observed that > > tty->termios.c_ispeed & tty->termios.c_ospeed set to 38400. I did not > > understood why it changes? > > Have you read the documentation on how to set custom baud rates? I > can't find the link to it at the moment, but it is very possible to do > that today, no special ioctls are needed at all. I think someone was > finally working on getting glibc to support it directly, but I do not > know if those patches ever got merged, so you would just have to "open > code" it in userspace if you want to do this. I could not find clear documentation on this, I’m very much thankful if someone point me on this. I thought of exploring TIOCGSERIAL and TIOCSSERIAL Ioctl’s to set custom baud rates. Now it looks like I should read the kernel code to understand how to achieve this without special ioctls. > > good luck! > > greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: tty: uart: custom speed 2019-03-04 15:23 ` Subhashini Rao Beerisetty @ 2019-03-04 17:16 ` Vladimir Zapolskiy 2019-03-04 18:47 ` Grant Edwards 1 sibling, 0 replies; 6+ messages in thread From: Vladimir Zapolskiy @ 2019-03-04 17:16 UTC (permalink / raw) To: Subhashini Rao Beerisetty; +Cc: Greg KH, linux-serial, kernelnewbies On 03/04/2019 05:23 PM, Subhashini Rao Beerisetty wrote: > On Mon, Mar 4, 2019 at 8:27 PM Greg KH <gregkh@linuxfoundation.org> wrote: >> >> On Mon, Mar 04, 2019 at 08:19:44PM +0530, Subhashini Rao Beerisetty wrote: >>> On Mon, Mar 4, 2019 at 6:53 PM Greg KH <gregkh@linuxfoundation.org> wrote: >>>> >>>> On Mon, Mar 04, 2019 at 05:46:54PM +0530, Subhashini Rao Beerisetty wrote: >>>>> Hi All, >>>>> >>>>> >>>>> I’ve an UART ports on Xilinx FPGA board and it gets connected to PC >>>>> via PCIe bus. I could not find any kernel serial driver which supports >>>>> our hardware so I plan to develop a new driver. I see two approaches >>>>> to develop an UART driver i.e. either by using tty_register_driver() >>>>> or an uart_register_driver(). >>>>> >>>>> >>>>> Regarding my UART module, it has a counter of 16 bits and runs on a >>>>> 32Mhz clock. It supports all the standard & non-standard baud’s up to >>>>> 4Mbps. >>>> >>>> What type of UART is it? Odds are it is based on an existing design, no >>>> one creates a brand-new UART anymore. Hopefully. If not, what a >>>> waste... >>> >>> For UART type, I see the permitted types are none, 8250, 16450, 16550, >>> 16550A, 16650, 16650V2, 16654, 16750, 16850, 16950, and 16954 etc. >>> Looking into the data sheet I haven’t found any register or parameter >>> defining any of those UART types. Is ‘UART type’ is determined from a >>> register settings point of view or a pinout point of view? >> >> register settings point of view. >> >> I suggest you do some basic research into how UARTs work before >> continuing with this effort, it will save you a lot of time in the end >> :) > > Thanks for you suggestion. I will study on this, I’m glad if you can > point some good documentation links on this. > >> >>>>> If I used struct tty_operations, I noticed that baud rate changing is >>>>> done via “.set_termios” API, but this method only supports standard >>>>> baud rates. I’d like to know why this API does not support >>>>> non-standard baud rates? >>>> >>>> Why do you think it does not? >>> From data sheet point of view I'm clear on how to set the non-standard >>> baud rate, even I exposed a custom Ioctl for this. But here I’m trying >>> to understand how it is achieved by using available UART kernel >>> framework. >>> For non-standard baud rate requests, observed that >>> tty->termios.c_ispeed & tty->termios.c_ospeed set to 38400. I did not >>> understood why it changes? >> >> Have you read the documentation on how to set custom baud rates? I >> can't find the link to it at the moment, but it is very possible to do >> that today, no special ioctls are needed at all. I think someone was >> finally working on getting glibc to support it directly, but I do not >> know if those patches ever got merged, so you would just have to "open >> code" it in userspace if you want to do this. > > I could not find clear documentation on this, I’m very much thankful > if someone point me on this. I thought of exploring TIOCGSERIAL and > TIOCSSERIAL Ioctl’s to set custom baud rates. Now it looks like I > should read the kernel code to understand how to achieve this without > special ioctls. > You should try to set a custom baudrate with help of TCSETS2: ----8<---- static int set_speed(int fd, speed_t speed) { struct termios2 tio; int ret; ret = ioctl(fd, TCGETS2, &tio); if (ret) { printf("TCGETS2 failed: %d\n", ret); return ret; } tio.c_cflag &= ~CBAUD; tio.c_cflag |= BOTHER; tio.c_ispeed = speed; tio.c_ospeed = speed; ret = ioctl(fd, TCSETS2, &tio); if (ret) { printf("TCSETS2 failed to set speed %u: %d\n", speed, ret); return ret; } return 0; } ----8<---- -- Best wishes, Vladimir _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: tty: uart: custom speed 2019-03-04 15:23 ` Subhashini Rao Beerisetty 2019-03-04 17:16 ` Vladimir Zapolskiy @ 2019-03-04 18:47 ` Grant Edwards 1 sibling, 0 replies; 6+ messages in thread From: Grant Edwards @ 2019-03-04 18:47 UTC (permalink / raw) To: kernelnewbies; +Cc: linux-serial On 2019-03-04, Subhashini Rao Beerisetty <subhashbeerisetty@gmail.com> wrote: > On Mon, Mar 4, 2019 at 8:27 PM Greg KH <gregkh@linuxfoundation.org> wrote: > >> Have you read the documentation on how to set custom baud rates? I >> can't find the link to it at the moment, but it is very possible to do >> that today, no special ioctls are needed at all. I think someone was >> finally working on getting glibc to support it directly, but I do not >> know if those patches ever got merged, so you would just have to "open >> code" it in userspace if you want to do this. > > I could not find clear documentation on this, I’m very much thankful > if someone point me on this. I thought of exploring TIOCGSERIAL and > TIOCSSERIAL Ioctl’s to set custom baud rates. Now it looks like I > should read the kernel code to understand how to achieve this without > special ioctls. You use the termios2 structure and TCGETS2/TCSETS ioctl calls: http://www.panix.com/~grante/arbitrary-baud.c -- Grant _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* tty: uart: custom speed @ 2019-03-04 12:12 Subhashini Rao Beerisetty 0 siblings, 0 replies; 6+ messages in thread From: Subhashini Rao Beerisetty @ 2019-03-04 12:12 UTC (permalink / raw) To: kernelnewbies; +Cc: linux-tty Hi All, I’ve an UART ports on Xilinx FPGA board and it gets connected to PC via PCIe bus. I could not find any kernel serial driver which supports our hardware so I plan to develop a new driver. I see two approaches to develop an UART driver i.e. either by using tty_register_driver() or an uart_register_driver(). Regarding my UART module, it has a counter of 16 bits and runs on a 32Mhz clock. It supports all the standard & non-standard baud’s up to 4Mbps. If I used struct tty_operations, I noticed that baud rate changing is done via “.set_termios” API, but this method only supports standard baud rates. I’d like to know why this API does not support non-standard baud rates? Okay, what methods a good driver should implement to support non-standard baud rates? Thanks _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-03-04 18:47 UTC | newest]
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[not found] ` <20190304132302.GA9869@kroah.com>
2019-03-04 14:49 ` tty: uart: custom speed Subhashini Rao Beerisetty
2019-03-04 14:57 ` Greg KH
2019-03-04 15:23 ` Subhashini Rao Beerisetty
2019-03-04 17:16 ` Vladimir Zapolskiy
2019-03-04 18:47 ` Grant Edwards
2019-03-04 12:12 Subhashini Rao Beerisetty
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