Heyi, Yes. I think computing the poll rate is a good addition to the TerminalDxe module.
If any of the information required to compute the rate is not available, then the #define default rate can be used. Do you want to prepare a patch with this enhancement? Thanks, Mike >-----Original Message----- >From: edk2-devel [mailto:[email protected]] On Behalf Of Heyi Guo >Sent: Tuesday, November 10, 2015 5:27 PM >To: Kinney, Michael D; [email protected] >Cc: Tian, Feng >Subject: Re: [edk2] [RFC] Adaptively set serial terminal input polling interval > > > >On 11/11/2015 04:34 AM, Kinney, Michael D wrote: >> Heyi, >> >> All timers in UEFI are the minimum time. So the only way to guarantee that >> a FIFO will never overflow is to use flow control. >> >> Setting the poll rate based on FIFO depth and baud rate, data bits, and stop >> bits with flow control disabled means it should work >most of the time, but another UEFI event notification function running at the >same TPL or higher can block the Terminal event >notification function and input characters could be lost. >> >> I agree that the current 20ms periodic timer can overflow depending in the >> FIFO depth and the baud rate, and that we could reduce >data loss in flow control disabled configurations if this periodic rate was >computed instead of using a hard coded #define. Another >constraint is the system timer interrupt rate provided by the Timer >Architectural Protocol. A request for a periodic timer event that is >faster than the current system timer rate will call the event notification >function at the rate of the system timer. So even if you >reduce the periodic timer event time to a computed value, the time between >event notification function calls may not change. >Totally agree. However normally we will have platform configuration >interface for interrupt rate of system timer, like PCD or even driver >override, but I can't find any interface to configure polling rate of >the terminal driver, and I really don't like to override the whole >terminal driver when I only want to change the polling rate :). That's >the reason why I want to make a patch for terminal driver. > >> >> In order to prevent overflows, I think the timer rate in 100ns units could >> be computed as follows: >> >> Receive FIFO depth * (1 + DataBits + StopBits) * 10,000,000 >> >> ---------------------------------------------------------------------------------- >> BaudRate >> >> For example, a 16 byte receive FIFO with 8 data bits and 1 stop bit at >> 115200 would be: >> >> 16 * (1 + 8 + 1) * 10,000,000 / 115200 = 15277 >> >> Which is 0.00153 seconds or 1.53 ms. >Can I consider this as your agreement on calculating polling rate in >terminal driver? > >After all, really appreciate your detailed answer on this issue. > >Heyi > >> >> Best regards, >> >> Mike >> >>> -----Original Message----- >>> From: edk2-devel [mailto:[email protected]] On Behalf Of Heyi >>> Guo >>> Sent: Monday, November 09, 2015 10:23 PM >>> To: Kinney, Michael D; [email protected] >>> Cc: Tian, Feng >>> Subject: Re: [edk2] [RFC] Adaptively set serial terminal input polling >>> interval >>> >>> Hi Michael, >>> >>> Yes we can see terminal input truncated when we use copy-paste to input >>> characters. >>> >>> I don't quite understand the relationship between SerialInTimeOut and >>> timer event poll rate; and I don't see the periodic timer rate is to be >>> updated later; we are using 0.02ms period all over, aren't we? >>> >>> If the timer event polls the serial device at a fixed rate, how can we >>> guarantee the FIFO of the device will not overflow during a burst input? >>> >>> Thanks. >>> >>> On 11/10/2015 01:25 AM, Kinney, Michael D wrote: >>>> Heyi, >>>> >>>> The function TerminalConInTimerHandler () computes a timeout based on the >>>> baud rate, data bits, and stop bits >>>> >>>> // >>>> // According to BAUD rate to calculate the timeout value. >>>> // >>>> SerialInTimeOut = (1 + Mode->DataBits + Mode->StopBits) * 2 * >>>> 1000000 / (UINTN) Mode->BaudRate; >>>> >>>> The #define is used to set the initial periodic timer rate before the rest >>>> of the information to compute a timeout is known. >>>> >>>> Are you observing an issue? >>>> >>>> Mike >>>> >>>>> -----Original Message----- >>>>> From: edk2-devel [mailto:[email protected]] On Behalf Of >>>>> Heyi >>>>> Guo >>>>> Sent: Monday, November 09, 2015 1:48 AM >>>>> To: [email protected] >>>>> Cc: Tian, Feng >>>>> Subject: [edk2] [RFC] Adaptively set serial terminal input polling >>>>> interval >>>>> >>>>> Hi All, >>>>> >>>>> In MdeModulePkg/Universal/Console/TerminalDxe/TerminalDxe.inf, the >>>>> polling interval is fixed by macro: >>>>> >>>>> #define KEYBOARD_TIMER_INTERVAL 200000 // 0.02s >>>>> >>>>> However, this may cause fast input to be truncated on some platform. For >>>>> example, we have a serial console with below features: >>>>> 1. Baud rate: 115200 >>>>> 2. FIFO depth of UART device: 32 >>>>> >>>>> If we want to capture all input, we need to poll with the interval of 32 >>>>> / (115200 / (8 + 1 + 1)) = 2.8 ms, 8 + 1 + 1 for data bits + start bit + >>>>> stop bit. >>>>> >>>>> So, I suppose to use a PCD to set the interval per platform, or >>>>> calculate from serial IO protocol IO Mode, which contains FIFO depth and >>>>> data bits, etc, and we can use 200000 as the maximum for compatibility, >>>>> or default value when fifo depth is 0. >>>>> >>>>> Please let me know your comments. >>>>> >>>>> Thanks. >>>>> >>>>> Heyi >>>>> _______________________________________________ >>>>> edk2-devel mailing list >>>>> [email protected] >>>>> https://lists.01.org/mailman/listinfo/edk2-devel >>> _______________________________________________ >>> edk2-devel mailing list >>> [email protected] >>> https://lists.01.org/mailman/listinfo/edk2-devel > >_______________________________________________ >edk2-devel mailing list >[email protected] >https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
