Re: MdeModulePkg/SerialDxe: Inconsistent timeout processing in SerialRead

["Zeng, Star" <star.zeng@intel.com>]

Oh, sorry, I forgot it because of busying on other things. I will post it soon.
Thanks for your reminder.

Star
-----Original Message-----
From: Heyi Guo [mailto:heyi.guo@linaro.org] 
Sent: Friday, August 4, 2017 4:03 PM
To: Zeng, Star <star.zeng@intel.com>; edk2-devel@lists.01.org; Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek (lersek@redhat.com) <lersek@redhat.com>
Subject: Re: [edk2] MdeModulePkg/SerialDxe: Inconsistent timeout processing in SerialRead

Hi Star,

The patch works well on our platform. Would you merge it to EDK2 main stream or do you like me to post it to the mailing-list?

Thanks and regards,

Gary (Heyi Guo)


在 7/18/2017 6:59 PM, Heyi Guo 写道:
> Hi Star,
>
> I think your proposed patch is fine.
>
> Thanks.
>
> Gary (Heyi Guo)
>
>
> 在 7/18/2017 4:39 PM, Zeng, Star 写道:
>> Gary,
>> SerialDxe is a wrapper of SerialPortLib to produce serial io protocol.
>> If let SerialDxe to handle the TimeOut, seemingly it can only check
>> SerialPortPoll() and read data by SerialPortRead() one byte by one 
>> byte, for example like below.
>> Do you have any proposed patch?
>>
>> Ray and Laszlo,
>> Do you have any comments?
>>
>>
>> ====================
>> debf0d1b85e7a30defd29838abb20a44dd9ec69b
>>   MdeModulePkg/Universal/SerialDxe/SerialIo.c | 18 ++++++++++++++++--
>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/MdeModulePkg/Universal/SerialDxe/SerialIo.c
>> b/MdeModulePkg/Universal/SerialDxe/SerialIo.c
>> index d2383e56dd8f..b05603d7f3b5 100644
>> --- a/MdeModulePkg/Universal/SerialDxe/SerialIo.c
>> +++ b/MdeModulePkg/Universal/SerialDxe/SerialIo.c
>> @@ -465,11 +465,25 @@ SerialRead (
>>     )
>>   {
>>     UINTN Count;
>> +  UINTN TimeOut;
>>       Count = 0;
>>   -  if (SerialPortPoll ()) {
>> -    Count = SerialPortRead (Buffer, *BufferSize);
>> +  while (Count < *BufferSize) {
>> +    TimeOut = 0;
>> +    while (TimeOut < mSerialIoMode.TimeOut) {
>> +      if (SerialPortPoll ()) {
>> +        break;
>> +      }
>> +      gBS->Stall (10);
>> +      TimeOut += 10;
>> +    }
>> +    if (TimeOut >= mSerialIoMode.TimeOut) {
>> +      break;
>> +    }
>> +    SerialPortRead (Buffer, 1);
>> +    Count++;
>> +    Buffer = (VOID *) ((UINT8 *) Buffer + 1);
>>     }
>>       if (Count != *BufferSize) {
>> ====================
>>
>>
>> Thanks,
>> Star
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf 
>> Of Heyi Guo
>> Sent: Monday, July 17, 2017 12:23 PM
>> To: edk2-devel@lists.01.org
>> Subject: [edk2] MdeModulePkg/SerialDxe: Inconsistent timeout 
>> processing in SerialRead
>>
>> Hi Folks,
>>
>> In SerialRead function in 
>> MdeModulePkg/Universal/SerialDxe/SerialIo.c,
>> it seems the timeout processing in SerialRead is not consistent.
>>
>> Since SerialPortPoll only checks the status of serial port and 
>> returns immediately, and SerialPortRead does not really implement a 
>> time out mechanism and will always wait for enough input, it will 
>> cause below
>> results:
>>
>> 1. If there is no serial input at all, this interface will return 
>> timeout immediately without any waiting;
>>
>> 2. If there is A characters in serial port FIFO, and caller requires
>> A+1 characters, it will wait until a new input is coming and timeout
>> will not really occur.
>>
>> As SerialPortLib is a simple library implementation, I think it is 
>> better to improve SerialIoDxe driver instead of SerialPortLib.
>>
>> Please let me know your comments about this.
>>
>> Thanks and regards,
>>
>> Gary (Heyi Guo)
>>
>> EFI_STATUS
>> EFIAPI
>> SerialRead (
>>     IN EFI_SERIAL_IO_PROTOCOL *This,
>>     IN OUT UINTN              *BufferSize,
>>     OUT VOID                  *Buffer
>>     )
>> {
>>     UINTN Count;
>>
>>     Count = 0;
>>
>>     if (SerialPortPoll ()) {
>>       Count = SerialPortRead (Buffer, *BufferSize);
>>     }
>>
>>     if (Count != *BufferSize) {
>>       *BufferSize = Count;
>>       return EFI_TIMEOUT;
>>     }
>>
>>     return EFI_SUCCESS;
>> }
>>
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>