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SubjectRe: [PATCH net v3 1/1] igc: read before write to SRRCTL register


On 14/04/2023 17.49, 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.
>
> Command on DUT:
> sudo ./xdp_hw_metadata <interface name>
>
> Command on Link Partner:
> echo -n skb | nc -u -q1 <destination IPv4 addr> 9092
>
> Result before this patch:
> skb hwtstamp is not found!
>
> Result after this patch:
> found skb hwtstamp = 1677800973.642836757
>
> Optionally, read PHC to confirm the values obtained are almost the same:
> Command:
> sudo ./testptp -d /dev/ptp0 -g
> Result:
> clock time: 1677800973.913598978 or Fri Mar 3 07:49:33 2023
>
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Cc: <stable@vger.kernel.org> # 5.14+
> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
> Reviewed-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---

LGTM, thank for the adjustments :-)

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>

> v2 -> v3: Refactor SRRCTL definitions to more human readable definitions
> v1 -> v2: Fix indention
> ---
> drivers/net/ethernet/intel/igc/igc_base.h | 11 ++++++++---
> drivers/net/ethernet/intel/igc/igc_main.c | 7 +++++--
> 2 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_base.h b/drivers/net/ethernet/intel/igc/igc_base.h
> index 7a992befca24..9f3827eda157 100644
> --- a/drivers/net/ethernet/intel/igc/igc_base.h
> +++ b/drivers/net/ethernet/intel/igc/igc_base.h
> @@ -87,8 +87,13 @@ 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_DESCTYPE_ADV_ONEBUF 0x02000000
> +#define IGC_SRRCTL_BSIZEPKT_MASK GENMASK(6, 0)
> +#define IGC_SRRCTL_BSIZEPKT(x) FIELD_PREP(IGC_SRRCTL_BSIZEPKT_MASK, \
> + (x) / 1024) /* in 1 KB resolution */
> +#define IGC_SRRCTL_BSIZEHDR_MASK GENMASK(13, 8)
> +#define IGC_SRRCTL_BSIZEHDR(x) FIELD_PREP(IGC_SRRCTL_BSIZEHDR_MASK, \
> + (x) / 64) /* in 64 bytes resolution */
> +#define IGC_SRRCTL_DESCTYPE_MASK GENMASK(27, 25)
> +#define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF FIELD_PREP(IGC_SRRCTL_DESCTYPE_MASK, 1)
>
> #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..a2d823e64609 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -641,8 +641,11 @@ 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 |= buf_size >> IGC_SRRCTL_BSIZEPKT_SHIFT;
> + srrctl = rd32(IGC_SRRCTL(reg_idx));
> + srrctl &= ~(IGC_SRRCTL_BSIZEPKT_MASK | IGC_SRRCTL_BSIZEHDR_MASK |
> + IGC_SRRCTL_DESCTYPE_MASK);
> + srrctl |= IGC_SRRCTL_BSIZEHDR(IGC_RX_HDR_LEN);
> + srrctl |= IGC_SRRCTL_BSIZEPKT(buf_size);
> srrctl |= IGC_SRRCTL_DESCTYPE_ADV_ONEBUF;
>
> wr32(IGC_SRRCTL(reg_idx), srrctl);

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