[RTEMS Project] #4719: risc-v fe310 console driver uart read error

[RTEMS trac]

#4719: risc-v fe310 console driver uart read error
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  Reporter:  Alan Cudmore  |      Owner:  (none)
      Type:  defect        |     Status:  new
  Priority:  normal        |  Milestone:
 Component:  bsps          |    Version:  6
  Severity:  normal        |   Keywords:  risc-v, uart
Blocked By:                |   Blocking:
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 In the riscv/riscv fe310_uart_read function, the uart RX data/status
 register is read twice when reading a character: once for the status, then
 a second time when reading the data. Reading the RX data/status register
 twice discards the input data from the first read.

 It can be fixed by first reading the RX data/status register into a local
 variable.

 This was verified on a Kendryte K210 CPU which uses the same SiFive UART.
 I will submit a patch to fix it.

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Ticket URL: <http://devel.rtems.org/ticket/4719>
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