Heyi, I think it should be ok to always calculate it.
I think the only time the #define default rate should be used is if the BaudRate is 0. Similar to setting the SerialInTimeOut, you can check in the periodic timer event notification function to see if the Baud Rate, Data Bits, Stop Bits, or Receive FIFO depth have changed, and if they have, compute and set the new periodic timer rate for the event. Mike >-----Original Message----- >From: Heyi Guo [mailto:heyi....@linaro.org] >Sent: Tuesday, November 10, 2015 7:07 PM >To: Kinney, Michael D; edk2-devel@lists.01.org >Cc: Tian, Feng >Subject: Re: [edk2] [RFC] Adaptively set serial terminal input polling interval > > > >On 11/11/2015 10:06 AM, Kinney, Michael D wrote: >> 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? >Sure, it's my pleasure. > >Do you think it is necessary to still use the default rate if the >calculated result is *larger* than it, to make it back compatible? It is >possible some old code has wrong FIFO depth stated. > >Thanks. >> >> Thanks, >> >> Mike >> >>> -----Original Message----- >>> From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of Heyi >>> Guo >>> Sent: Tuesday, November 10, 2015 5:27 PM >>> To: Kinney, Michael D; edk2-devel@lists.01.org >>> 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:edk2-devel-boun...@lists.01.org] On Behalf Of >>>>> Heyi Guo >>>>> Sent: Monday, November 09, 2015 10:23 PM >>>>> To: Kinney, Michael D; edk2-devel@lists.01.org >>>>> 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:edk2-devel-boun...@lists.01.org] On Behalf Of >>>>>>> Heyi >>>>>>> Guo >>>>>>> Sent: Monday, November 09, 2015 1:48 AM >>>>>>> To: edk2-devel@lists.01.org >>>>>>> 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 >>>>>>> edk2-devel@lists.01.org >>>>>>> https://lists.01.org/mailman/listinfo/edk2-devel >>>>> _______________________________________________ >>>>> edk2-devel mailing list >>>>> edk2-devel@lists.01.org >>>>> https://lists.01.org/mailman/listinfo/edk2-devel >>> _______________________________________________ >>> edk2-devel mailing list >>> edk2-devel@lists.01.org >>> https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
