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SubjectRe: [PATCH net 1/1] igc: read before write to SRRCTL register

On 13/04/2023 17.12, Song Yoong Siang wrote:
> igc_configure_rx_ring() function will be called as part of XDP program
> setup. If Rx hardware timestamp is enabled prio to XDP program setup,
> this timestamp enablement will be overwritten when buffer size is
> written into SRRCTL register.
>
> Thus, this commit read the register value before write to SRRCTL
> register. This commit is tested by using xdp_hw_metadata bpf selftest
> tool. The tool enables Rx hardware timestamp and then attach XDP program
> to igc driver. It will display hardware timestamp of UDP packet with
> port number 9092. Below are detail of test steps and results.
[...]
> diff --git a/drivers/net/ethernet/intel/igc/igc_base.h b/drivers/net/ethernet/intel/igc/igc_base.h
> index 7a992befca24..b95007d51d13 100644
> --- a/drivers/net/ethernet/intel/igc/igc_base.h
> +++ b/drivers/net/ethernet/intel/igc/igc_base.h
> @@ -87,8 +87,11 @@ union igc_adv_rx_desc {
> #define IGC_RXDCTL_SWFLUSH 0x04000000 /* Receive Software Flush */
>
> /* SRRCTL bit definitions */
> -#define IGC_SRRCTL_BSIZEPKT_SHIFT 10 /* Shift _right_ */
> -#define IGC_SRRCTL_BSIZEHDRSIZE_SHIFT 2 /* Shift _left_ */
> +#define IGC_SRRCTL_BSIZEPKT_MASK GENMASK(6, 0)
> +#define IGC_SRRCTL_BSIZEPKT_SHIFT 10 /* Shift _right_ */
> +#define IGC_SRRCTL_BSIZEHDRSIZE_MASK GENMASK(13, 8)
> +#define IGC_SRRCTL_BSIZEHDRSIZE_SHIFT 2 /* Shift _left_ */
> +#define IGC_SRRCTL_DESCTYPE_MASK GENMASK(27, 25)
> #define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF 0x02000000
>
> #endif /* _IGC_BASE_H */
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 25fc6c65209b..de7b21c2ccd6 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -641,7 +641,10 @@ static void igc_configure_rx_ring(struct igc_adapter *adapter,
> else
> buf_size = IGC_RXBUFFER_2048;
>
> - srrctl = IGC_RX_HDR_LEN << IGC_SRRCTL_BSIZEHDRSIZE_SHIFT;
> + srrctl = rd32(IGC_SRRCTL(reg_idx));
> + srrctl &= ~(IGC_SRRCTL_BSIZEPKT_MASK | IGC_SRRCTL_BSIZEHDRSIZE_MASK |
> + IGC_SRRCTL_DESCTYPE_MASK);
^^
Please fix indention, moving IGC_SRRCTL_DESCTYPE_MASK such that it
aligns with IGC_SRRCTL_BSIZEPKT_MASK. This make is easier for the eye
to spot that it is part of the negation (~).

> + srrctl |= IGC_RX_HDR_LEN << IGC_SRRCTL_BSIZEHDRSIZE_SHIFT;
> srrctl |= buf_size >> IGC_SRRCTL_BSIZEPKT_SHIFT;
> srrctl |= IGC_SRRCTL_DESCTYPE_ADV_ONEBUF;
>

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