Ard, Many handlers running at the same TPL are ok as long as each of the handlers run for very short periods of time. Any event handlers that execute as raised TPL for extended periods of time will impact other event handlers.
In a worst case scenario, if the execution time at raised TPL in a handler or group of handlers is greater than or equal to their poll rates, then a live lock condition can occur where the code at lower TPLs never gets to make forward progress. This means that event handlers at raised TPL need to be very efficient and do their work quickly and potentially just set some flags or queue some data for work to be done at a lower TPL at a slower event rate. Mike > -----Original Message----- > From: Ard Biesheuvel [mailto:[email protected]] > Sent: Monday, March 28, 2016 11:08 PM > To: Kinney, Michael D <[email protected]> > Cc: Heyi Guo <[email protected]>; Ni, Ruiyu <[email protected]>; edk2- > [email protected]; Tian, Feng <[email protected]>; Zeng, Star > <[email protected]> > Subject: Re: [edk2] [PATCH v2 3/3] MdeModulePkg/TerminalDxe: Set polling rate > by serial > IO mode > > On 29 March 2016 at 06:09, Kinney, Michael D <[email protected]> > wrote: > > Ard, > > > > What is the timer rate in the system you are using? > > > > I am going to let Heyi respond with the actual numbers. > > > The timer event rate of a UEFI driver can not go any faster or a smaller > > granularity > than the system timer rate. > > > > The original formula may be correct, but may not be compensating for the > > granularity > of the timer rate. > > > > Is the issue also resolved if you increase the system timer tick rate? > > > > I agree that there is likely a significant quantization error once the > poll rate approaches the system tick rate. But I think Heyi's analysis > is correct that handlers executing at the same TPL may cause jitter > that needs to be compensated for by bias towards zero on the poll > rate. > > > Ard. > > >> -----Original Message----- > >> From: edk2-devel [mailto:[email protected]] On Behalf Of > >> Heyi Guo > >> Sent: Monday, March 28, 2016 8:06 PM > >> To: Ard Biesheuvel <[email protected]>; Ni, Ruiyu > >> <[email protected]> > >> Cc: [email protected]; Tian, Feng <[email protected]>; Zeng, Star > >> <[email protected]> > >> Subject: Re: [edk2] [PATCH v2 3/3] MdeModulePkg/TerminalDxe: Set polling > >> rate by > serial > >> IO mode > >> > >> > >> > >> On 03/25/2016 01:56 PM, Ard Biesheuvel wrote: > >> > On 25 March 2016 at 03:52, Ni, Ruiyu <[email protected]> wrote: > >> >> Heyi, > >> >> I was not able to remove the blue bar in the beginning of every line if > >> >> I > embedded > >> my reply. > >> >> So I will directly write down here. > >> >> > >> >> > >> >> 1. I would like to know in what circumstance the key loss happens. > >> >> Because your UART hardware has 32 FIFO buffer to receive the keys. > >> >> A typical escape keys (corresponding to Arrow Left, Arrow Right, or > >> >> F1-F12) > >> combination > >> >> would only need 3-4 bytes. The FIFO buffer is sufficient to hold about > >> >> 10 > >> >> combinations. > >> >> > >> > The loss of input characters occurs typically when you copy-paste > >> > something into the terminal window. > >> > >> Thanks Ard for helping me to reply; that's really the case I want to fix :) > >> > >> > > >> >> 2. Your system's timer hardware is fast enough so your timer > >> >> callback can be > >> triggered > >> >> every 2 (2.78) ms, then terminal driver should be able to capture all > >> >> the escape > >> keys. > >> >> Now since terminal driver cannot capture all the escape keys, so you > >> >> guess the > >> callback is > >> >> not triggered every 2ms. > >> >> Can you find a way to prove it? for example, save the time every time > >> >> the > callback > >> is called. > >> >> Then after like 100 rounds of callback, dump all the 100 time values. > >> >> Let's see the real time interval value. > >> OK, I'll try that and let you know the result. > >> > >> Thanks and regards. > >> > >> Heyi > >> > >> >> > >> >> 3. I forget about the FIFO depth change. The FIFO depth change > >> >> doesn't cause > >> the device > >> >> > >> >> path reinstallation. I agree we need to detect the FIFO depth change in > >> >> timer > call > >> back > >> >> > >> >> to update the interval. > >> >> > >> >> > >> >> Regards, > >> >> Ray > >> >> > >> >> From: Heyi Guo [mailto:[email protected]] > >> >> Sent: Thursday, March 24, 2016 10:59 PM > >> >> To: Ni, Ruiyu <[email protected]>; [email protected] > >> >> Cc: Tian, Feng <[email protected]>; Zeng, Star <[email protected]> > >> >> Subject: Re: [edk2] [PATCH v2 3/3] MdeModulePkg/TerminalDxe: Set > >> >> polling rate by > >> serial IO mode > >> >> > >> >> Hi Ruiyu, > >> >> > >> >> I had seen the other comments and I just needed more time to think > >> >> about them :) > >> >> > >> >> Please see my comments below. > >> >> On 03/24/2016 03:26 PM, Ni, Ruiyu wrote: > >> >> Heyi, > >> >> I had 7 comments in previous mail. I guess you may miss the other > >> >> comments. > >> >> > >> >> What Timer driver are you using? How many ms does one system tick cost? > >> >> If you are using a less-precise timer driver/hardware, one tick may be > >> >> larger > than > >> >> what you expected. > >> >> We are using ArmPlatformPkg/Drivers/SP804TimerDxe/SP804TimerDxe.inf as > >> >> timer > driver. > >> >> The frequency of the timer is 200MHz. Timer interrupt period is set to > >> >> 1ms. > >> >> > >> >> > >> >> > >> >> And can you tell me all the UART parameters in your case? What timer > >> >> interval > >> >> did you get using the equation? > >> >> Baud rate = 115200 > >> >> FIFO depth = 32 > >> >> Parity = 0 > >> >> stop = 1 > >> >> Data size = 8 > >> >> Polling interval = (1 + 8 + 0 + 1) * 32 / 115200 = 0.00278 (2.78ms) > >> >> > >> >> And please continue to see my opinions for other comments below: > >> >> > >> >> > >> >> > >> >> Regards, > >> >> Ray > >> >> > >> >> > >> >>> -----Original Message----- > >> >>> From: Heyi Guo [mailto:[email protected]] > >> >>> Sent: Wednesday, March 23, 2016 5:44 PM > >> >>> To: Ni, Ruiyu <[email protected]><mailto:[email protected]>; edk2- > >> [email protected]<mailto:[email protected]> > >> >>> Cc: Tian, Feng <[email protected]><mailto:[email protected]>; > >> >>> Zeng, Star > >> <[email protected]><mailto:[email protected]>; Kinney, Michael D > >> <[email protected]><mailto:[email protected]> > >> >>> Subject: Re: [edk2] [PATCH v2 3/3] MdeModulePkg/TerminalDxe: Set > >> >>> polling rate by > >> serial IO mode > >> >>> > >> >>> Hi Ruiyu, > >> >>> > >> >>> Many thanks for your review. > >> >>> > >> >>> For questions 2#, I tested equation #1 with copy-paste on serial > >> >>> terminal, and found it still missing some characters when the FIFO was > >> >>> almost full (i.e. near the end of input). I think it is because time > >> >>> event is not real-time interrupt; it may be pending for equal or > >> >>> higher TPL. > >> >>> > >> >>> And a little faster polling rate tested well on real environment. > >> >>> > >> >>> Please let me know your suggestion. > >> >>> > >> >>> Regards. > >> >>> > >> >>> Heyi > >> >>> > >> >>> On 03/23/2016 04:03 PM, Ni, Ruiyu wrote: > >> >>>> Heyi, > >> >>>> I have comments in below. > >> >>>> > >> >>>> Regards, > >> >>>> Ray > >> >>>> > >> >>>> > >> >>>>> -----Original Message----- > >> >>>>> From: edk2-devel [mailto:[email protected]] On Behalf > >> >>>>> Of Heyi > Guo > >> >>>>> Sent: Thursday, March 17, 2016 10:37 PM > >> >>>>> To: [email protected]<mailto:[email protected]> > >> >>>>> Cc: Heyi Guo <[email protected]><mailto:[email protected]>; > >> >>>>> Tian, Feng > >> <[email protected]><mailto:[email protected]>; Zeng, Star > >> <[email protected]><mailto:[email protected]> > >> >>>>> Subject: [edk2] [PATCH v2 3/3] MdeModulePkg/TerminalDxe: Set polling > >> >>>>> rate by > >> serial IO mode > >> >>>>> > >> >>>>> Calculate serial input polling rate according to parameters from > >> >>>>> serial IO mode as below, to fix potential input truncation with fixed > >> >>>>> polling interval 0.02s. > >> >>>>> > >> >>>>> Polling interval (100ns) = > >> >>>>> FifoDepth * (ParityBits + StopBits + DataBits) * 10,000,000 / > >> >>>>> BaudRate > >> >>>> 1. The above equation (let's call it equation #1) looks good. > >> >>>> > >> >> Sorry I think I missed the start bit, which should always be 1 bit. > >> >> > >> >> > >> >>>>> However, as UEFI events will probably delayed by other code of higher > >> >>>>> TPL, we use below equation to make polling rate fast enough: > >> >>>>> > >> >>>>> FifoDepth * DataBits * 10,000,000 * 2 / (BaudRate * 3) > >> >>>> 2. Can you tell me why you multiple two in the left of "/" and > >> >>>> multiple 3 in > the > >> right? > >> >>>> Did you meet any real problem when using the original equation (#1)? > >> >>>> > >> >>>> I have more comments in below. > >> >>>> > >> >>>>> Signed-off-by: Heyi Guo > >> >>>>> <[email protected]><mailto:[email protected]> > >> >>>>> Cc: Feng Tian <[email protected]><mailto:[email protected]> > >> >>>>> Cc: Star Zeng <[email protected]><mailto:[email protected]> > >> >>>>> --- > >> >>>>> .../Universal/Console/TerminalDxe/Terminal.c | 5 +- > >> >>>>> .../Universal/Console/TerminalDxe/Terminal.h | 27 ++++++++- > >> >>>>> .../Universal/Console/TerminalDxe/TerminalConIn.c | 68 > >> >>>>> ++++++++++++++++++++++ > >> >>>>> 3 files changed, 98 insertions(+), 2 deletions(-) > >> >>>>> > >> >>>>> diff --git a/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.c > >> >>>>> b/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.c > >> >>>>> index 5adaa97..db790f3 100644 > >> >>>>> --- a/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.c > >> >>>>> +++ b/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.c > >> >>>>> @@ -71,6 +71,7 @@ TERMINAL_DEV mTerminalDevTemplate = { > >> >>>>> }, > >> >>>>> NULL, // TerminalConsoleModeData > >> >>>>> 0, // SerialInTimeOut > >> >>>>> + DEFAULT_KEYBOARD_TIMER_INTERVAL, // KeyboardTimerInterval > >> >>>> 3. Can you remove the default timer interval? > >> >>>> We should be able to calculate the timer interval from the default > >> >>>> setting (DataBits, StopBits, BaudRate, etc). > >> >>>> > >> >> See below. > >> >> > >> >>>>> NULL, // RawFifo > >> >>>>> NULL, // UnicodeFiFo > >> >>>>> @@ -984,10 +985,12 @@ TerminalDriverBindingStart ( > >> >>>>> ); > >> >>>>> ASSERT_EFI_ERROR (Status); > >> >>>>> > >> >>>>> + TerminalDevice->KeyboardTimerInterval = > >> >>>>> GetKeyboardTimerInterval (Mode); > >> >>>>> + > >> >>>>> Status = gBS->SetTimer ( > >> >>>>> TerminalDevice->TimerEvent, > >> >>>>> TimerPeriodic, > >> >>>>> - KEYBOARD_TIMER_INTERVAL > >> >>>>> + TerminalDevice->KeyboardTimerInterval > >> >>>>> ); > >> >>>>> ASSERT_EFI_ERROR (Status); > >> >>>>> > >> >>>>> diff --git a/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.h > >> >>>>> b/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.h > >> >>>>> index 269d2ae..58d5664 100644 > >> >>>>> --- a/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.h > >> >>>>> +++ b/MdeModulePkg/Universal/Console/TerminalDxe/Terminal.h > >> >>>>> @@ -68,7 +68,7 @@ typedef struct { > >> >>>>> UINTN Rows; > >> >>>>> } TERMINAL_CONSOLE_MODE_DATA; > >> >>>>> > >> >>>>> -#define KEYBOARD_TIMER_INTERVAL 200000 // 0.02s > >> >>>>> +#define DEFAULT_KEYBOARD_TIMER_INTERVAL 200000 // 0.02s > >> >>>> 4. Same question as #3. > >> >>>> > >> >>>>> #define TERMINAL_DEV_SIGNATURE SIGNATURE_32 ('t', 'm', 'n', 'l') > >> >>>>> > >> >>>>> @@ -91,6 +91,7 @@ typedef struct { > >> >>>>> EFI_SIMPLE_TEXT_OUTPUT_MODE SimpleTextOutputMode; > >> >>>>> TERMINAL_CONSOLE_MODE_DATA *TerminalConsoleModeData; > >> >>>>> UINTN SerialInTimeOut; > >> >>>>> + UINT64 KeyboardTimerInterval; > >> >>>>> RAW_DATA_FIFO *RawFiFo; > >> >>>>> UNICODE_FIFO *UnicodeFiFo; > >> >>>>> EFI_KEY_FIFO *EfiKeyFiFo; > >> >>>>> @@ -1358,4 +1359,28 @@ TerminalConInTimerHandler ( > >> >>>>> IN EFI_EVENT Event, > >> >>>>> IN VOID *Context > >> >>>>> ); > >> >>>>> + > >> >>>>> +/** > >> >>>>> + Calculate input polling timer interval by serial IO mode. > >> >>>>> + > >> >>>>> + @param Mode Pointer to serial IO mode. > >> >>>>> + > >> >>>>> + @retval The required polling timer interval in 100ns. > >> >>>>> + > >> >>>>> +**/ > >> >>>>> +UINT64 > >> >>>>> +GetKeyboardTimerInterval ( > >> >>>>> + IN EFI_SERIAL_IO_MODE *Mode > >> >>>>> + ); > >> >>>>> + > >> >>>>> +/** > >> >>>>> + Update period of polling timer event. > >> >>>>> + > >> >>>>> + @param TerminalDevice The terminal device to update. > >> >>>>> +**/ > >> >>>>> +VOID > >> >>>>> +UpdatePollingRate ( > >> >>>>> + IN TERMINAL_DEV *TerminalDevice > >> >>>>> + ); > >> >>>>> + > >> >>>>> #endif > >> >>>>> diff --git > >> >>>>> a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c > >> >>>>> b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c > >> >>>>> index 2215df6..22349a0 100644 > >> >>>>> --- a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c > >> >>>>> +++ b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c > >> >>>>> @@ -502,6 +502,71 @@ TerminalConInWaitForKey ( > >> >>>>> } > >> >>>>> > >> >>>>> /** > >> >>>>> + Calculate input polling timer interval by serial IO mode. > >> >>>>> + > >> >>>>> + @param Mode Pointer to serial IO mode. > >> >>>>> + > >> >>>>> + @retval The required polling timer interval in 100ns. > >> >>>>> + > >> >>>>> +**/ > >> >>>>> +UINT64 > >> >>>>> +GetKeyboardTimerInterval ( > >> >>>>> + IN EFI_SERIAL_IO_MODE *Mode > >> >>>>> + ) > >> >>>>> +{ > >> >>>>> + UINT32 FifoDepth; > >> >>>>> + > >> >>>>> + if (Mode->BaudRate == 0) { > >> >>>>> + return DEFAULT_KEYBOARD_TIMER_INTERVAL; > >> >>>>> + } > >> >>>> 5. Now I understand you need the default timer interval for the > >> >>>> default > setting. > >> >>>> Because UEFI spec says when the baud rate has the value of 0 to > >> >>>> indicate the > >> device > >> >>>> runs at the device's *designed speed*. > >> >>>> But I still think you can calculate the timer interval assuming the > >> >>>> baudrate is > >> 115200. > >> >>>> Because if using 115200 the timer interval is about 0.001s which is > >> >>>> still > shorter > >> than 0.02s. > >> >>>> > >> >> Sounds good for me. > >> >> > >> >> > >> >>>>> + > >> >>>>> + FifoDepth = Mode->ReceiveFifoDepth; > >> >>>>> + // Fix incorrect FIFO depth > >> >>>>> + if (FifoDepth == 0) { > >> >>>>> + FifoDepth = 1; > >> >>>>> + } > >> >>>>> + > >> >>>>> + // We ignore stop bits and parity bit, and reduce the interval by > >> >>>>> 1/3, > >> >>>>> + // to make polling rate fast enough to avoid serial input > >> >>>>> truncation. > >> >>>>> + return DivU64x64Remainder ( > >> >>>>> + FifoDepth * Mode->DataBits * 10000000 * 2, > >> >>>>> + Mode->BaudRate * 3, > >> >>>>> + NULL > >> >>>>> + ); > >> >>>>> +} > >> >>>> 6. Same question. Can you use the original equation #1? > >> >>>> > >> >>>>> + > >> >>>>> + > >> >>>>> +/** > >> >>>>> + Update period of polling timer event. > >> >>>>> + > >> >>>>> + @param TerminalDevice The terminal device to update. > >> >>>>> +**/ > >> >>>>> +VOID > >> >>>>> +UpdatePollingRate ( > >> >>>>> + IN TERMINAL_DEV *TerminalDevice > >> >>>>> + ) > >> >>>>> +{ > >> >>>>> + UINT64 NewInterval; > >> >>>>> + EFI_STATUS Status; > >> >>>>> + > >> >>>>> + NewInterval = GetKeyboardTimerInterval > >> >>>>> (TerminalDevice->SerialIo->Mode); > >> >>>>> + > >> >>>>> + if (TerminalDevice->KeyboardTimerInterval == NewInterval) { > >> >>>>> + return; > >> >>>>> + } > >> >>>>> + > >> >>>>> + Status = gBS->SetTimer ( > >> >>>>> + TerminalDevice->TimerEvent, > >> >>>>> + TimerPeriodic, > >> >>>>> + NewInterval > >> >>>>> + ); > >> >>>>> + ASSERT_EFI_ERROR (Status); > >> >>>>> + > >> >>>>> + TerminalDevice->KeyboardTimerInterval = NewInterval; > >> >>>>> +} > >> >>>>> + > >> >>>>> + > >> >>>>> +/** > >> >>>>> Timer handler to poll the key from serial. > >> >>>>> > >> >>>>> @param Event Indicates the event that invoke > >> >>>>> this > >> function. > >> >>>>> @@ -560,6 +625,9 @@ TerminalConInTimerHandler ( > >> >>>>> TerminalDevice->SerialInTimeOut = SerialInTimeOut; > >> >>>>> } > >> >>>>> } > >> >>>>> + > >> >>>>> + UpdatePollingRate (TerminalDevice); > >> >>>> 7. All the parameters (baudrate, databits, stopbits,etc) are stored > >> >>>> in the UART > >> device path. > >> >>>> Any change to these parameters triggers the UART device path > >> >>>> reinstallation, > >> ultimately > >> >>>> triggers the Terminal driver's restart. > >> >>>> So the polling rate doesn't need to update here. > >> >>>> > >> >> How about FIFO depth change? > >> >> > >> >> Thanks for your review :) > >> >> > >> >> Heyi > >> >> > >> >> > >> >> > >> >>>>> + > >> >>>>> // > >> >>>>> // Check whether serial buffer is empty. > >> >>>>> // Skip the key transfer loop only if the SerialIo protocol > >> >>>>> instance > >> >>>>> -- > >> >>>>> 2.7.0 > >> >>>>> > >> >>>>> _______________________________________________ > >> >>>>> edk2-devel mailing list > >> >>>>> [email protected]<mailto:[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
