Forum Discussion
New ContributorPCIe P-Tile Flow Control
Hi Anat,
On P-tile IP, there is no handling required by user application when credit is consumed due to internally generated TLP. Just that the credit return to user is slower.
This means that HIP decrements new FC_update credits values before to pass them to the user application as TX credit limit when HIP has consumed internal credits.
In that sense user application will have less credits that once sent by PCIe link partner agent in FC_update DLLP.
For example, the RP send FC_update PD=20 and HIP had consumed 4 credits then user application will received PD=16 (TX credit limit signal) where previous TX credit limit value was PD=16 or less.
Does this acceptably answer your question?
Regards,
Wincent
New ContributorHi Wincent,
From your explanation, I understand
a. P-Tile HIP advertise infinite credite for CPL during initialization.
b. Value passed by the rx_buffer_limit* interface signal will not affect the value of credit advertised.
if this interface doesn't affect the credit advertised what is the actual use of this rx_buffer_limit* interface?
Regular ContributorHi Anat,
a. P-Tile HIP advertise infinite credite for CPL during initialization.
>> Yes, for P-tile, CPL credit is advertised as infinete
b. Value passed by the rx_buffer_limit* interface signal will not affect the value of credit advertised.
>> Yes, that is right Hip will only initialize credit to the link partner according to the value in the screenshot above (p-tile), and periodically advertise the credit to the link partner in accordance with the TLP received
Hope that clarified.
Regards,
Wincent_Altera
- anat
Hi,
"if this interface doesn't affect the credit advertised what is the actual use of this rx_buffer_limit* interface?" --- Please clarify this as well- Wincent_Altera
Hi Anat,
RX flow control interface provides information on the application's available RX buffer space to the PCIe Hard IP in a time-division multiplexing (TDM) manner. It reports the space available in number of TLPs.
The RX flow control interface is optional and disabled by default in the IP GUI. If disabled, it indicates that there is no limit in the application RX buffer space.
Hope this clarified.
Regards,
Wincent_Altera
