I have a problem with configuration the TIM1-ETR in stm32f1

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I want to use the external clock mode 2 but it dose not work ,configure the PA12 that connect to TIM1-ETR AND make push button pull down to send pulses to that pin(PA12) to detect high edge and make up count to the variable "upCount" in the code ,i thought there is a missed in the configuration ,can any one help me to find the wrong in the code