[v2] net/iavf: fix Rx queue interrupt setting

  For Rx-Queue Interrupt Setting, when vf rx interrupt
disable(INTENA=0), there are two ways to write back
descriptor to host memory:

1)Set WB_ON_ITR bit 0 to Interrupt Dynamic Control Register:
Completed descriptors are posted to host memory according to
the internal descriptor cache policy (in other words when a
full cache line is available for write-back).

A internal descriptor size is 16 bytes or 32 bytes, a cache
line size is 64 bytes or 128 bytes from datasheet :
PCIe Global Config 2 - GLPCI_CNF2 (0x000BE004; RO)
so the full cache line could contains 4 packets, it means
Network card will send 4 packets to host when a full cache line
is available.

2)Set WB_ON_ITR bit 1 to Interrupt Dynamic Control Register:
Completed descriptors also trigger the ITR. Following ITR
expiration, all leftover completed descriptors are posted to
host memory.

Network card will send packet to host even if only one
descriptor is completed.

Changing 1) to 2) to make sure VF send the packet to host even
if there is only one rx packet is ready in hardware.

Fixes: d6bde6b5eae9 ("net/avf: enable Rx interrupt")
Cc: stable@dpdk.org

Signed-off-by: Ke Zhang <ke1x.zhang@intel.com>
---
 v2:
  Add more explanation what's the issue and how we fix this
  issue in commit log.

 drivers/net/iavf/iavf_ethdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
  

> -----Original Message-----
> From: Ke Zhang <ke1x.zhang@intel.com>
> Sent: Friday, May 20, 2022 11:00 AM
> To: Li, Xiaoyun <xiaoyun.li@intel.com>; Wu, Jingjing <jingjing.wu@intel.com>;
> Xing, Beilei <beilei.xing@intel.com>; dev@dpdk.org
> Cc: Zhang, Ke1X <ke1x.zhang@intel.com>; stable@dpdk.org
> Subject: [PATCH v2] net/iavf: fix Rx queue interrupt setting
> 
> For Rx-Queue Interrupt Setting, when vf rx interrupt disable(INTENA=0), there
> are two ways to write back descriptor to host memory:
> 
> 1)Set WB_ON_ITR bit 0 to Interrupt Dynamic Control Register:
> Completed descriptors are posted to host memory according to the internal
> descriptor cache policy (in other words when a full cache line is available for
> write-back).
> 
> A internal descriptor size is 16 bytes or 32 bytes, a cache line size is 64 bytes or
> 128 bytes from datasheet :
> PCIe Global Config 2 - GLPCI_CNF2 (0x000BE004; RO) so the full cache line
> could contains 4 packets, it means Network card will send 4 packets to host
> when a full cache line is available.
> 
> 2)Set WB_ON_ITR bit 1 to Interrupt Dynamic Control Register:
> Completed descriptors also trigger the ITR. Following ITR expiration, all
> leftover completed descriptors are posted to host memory.
> 
> Network card will send packet to host even if only one descriptor is completed.
> 
> Changing 1) to 2) to make sure VF send the packet to host even if there is only
> one rx packet is ready in hardware.
> 
> Fixes: d6bde6b5eae9 ("net/avf: enable Rx interrupt")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ke Zhang <ke1x.zhang@intel.com>

Acked-by: Qi Zhang <qi.z.zhang@intel.com>

Applied to dpdk-next-net-intel.

Thanks
Qi