RE: [Patch net-next v6 2/7] r8169: add support for multi rx queues

[Javen]

>On Tue, 26 May 2026 16:11:12 +0800 javen wrote:
>> diff --git a/drivers/net/ethernet/realtek/r8169_main.c
>> b/drivers/net/ethernet/realtek/r8169_main.c
>> index 22e843baffc7..62bf77aa1ec8 100644
>> --- a/drivers/net/ethernet/realtek/r8169_main.c
>> +++ b/drivers/net/ethernet/realtek/r8169_main.c
>> @@ -74,9 +74,13 @@
>>  #define NUM_TX_DESC  256     /* Number of Tx descriptor registers */
>>  #define NUM_RX_DESC  256     /* Number of Rx descriptor registers */
>>  #define R8169_TX_RING_BYTES  (NUM_TX_DESC * sizeof(struct TxDesc))
>> -#define R8169_RX_RING_BYTES  (NUM_RX_DESC * sizeof(struct RxDesc))
>> +#define R8169_RX_RING_BYTES  ((NUM_RX_DESC + 1) * sizeof(struct
>> +RxDesc))
>
>AI bots are asking why the "+ 1"?

This + 1 is a workaround for the hardware DMA prefetcher. The H/W might aggressively fetch one more descriptor even after hitting the RingEnd mark. We allocated this extra dummy space as padding to prevent out-of-bounds access and potential IOMMU faults.

>
>>  #define R8169_TX_STOP_THRS   (MAX_SKB_FRAGS + 1)
>>  #define R8169_TX_START_THRS  (2 * R8169_TX_STOP_THRS)
>> +#define R8169_MAX_RX_QUEUES  8
>> +#define R8127_MAX_RX_QUEUES  8
>> +#define R8169_DEFAULT_RX_QUEUES      1
>> +#define R8169_MAX_TX_QUEUES  1
>>
>>  #define OCP_STD_PHY_BASE     0xa400
>>
>> @@ -441,6 +445,7 @@ enum rtl8125_registers {
>>       TxPoll_8125             = 0x90,
>>       LEDSEL3                 = 0x96,
>>       MAC0_BKP                = 0x19e0,
>> +     RDSAR_Q1_LOW            = 0x4000,
>>       RSS_CTRL_8125           = 0x4500,
>>       Q_NUM_CTRL_8125         = 0x4800,
>>       EEE_TXIDLE_TIMER_8125   = 0x6048,
>> @@ -728,6 +733,21 @@ enum rtl_dash_type {
>>       RTL_DASH_25_BP,
>>  };
>>
>> +enum rx_desc_ring_type {
>> +     RX_DESC_RING_TYPE_DEFAULT,
>> +     RX_DESC_RING_TYPE_RSS,
>> +};
>> +
>> +struct rtl8169_rx_ring {
>> +     u32 index;                                      /* Rx queue index */
>> +     u32 cur_rx;                                     /* Index of next Rx pkt. */
>> +     u32 dirty_rx;                                   /* Index for recycling. */
>> +     struct RxDesc *rx_desc_array;                   /* array of Rx Desc*/
>> +     dma_addr_t rx_desc_phy_addr[NUM_RX_DESC];       /* Rx data buffer
>physical dma address */
>> +     dma_addr_t rx_phy_addr;                         /* Rx desc physical address */
>> +     struct page *rx_databuff[NUM_RX_DESC];          /* Rx data buffers */
>> +};
>> +
>>  struct rtl8169_private {
>>       void __iomem *mmio_addr;        /* memory map physical address */
>>       struct pci_dev *pci_dev;
>> @@ -735,20 +755,18 @@ struct rtl8169_private {
>>       struct phy_device *phydev;
>>       enum mac_version mac_version;
>>       enum rtl_dash_type dash_type;
>> -     u32 cur_rx; /* Index into the Rx descriptor buffer of next Rx pkt. */
>>       u32 cur_tx; /* Index into the Tx descriptor buffer of next Rx pkt. */
>>       u32 dirty_tx;
>>       struct TxDesc *TxDescArray;     /* 256-aligned Tx descriptor ring */
>> -     struct RxDesc *RxDescArray;     /* 256-aligned Rx descriptor ring */
>>       dma_addr_t TxPhyAddr;
>> -     dma_addr_t RxPhyAddr;
>> -     struct page *Rx_databuff[NUM_RX_DESC];  /* Rx data buffers */
>>       struct ring_info tx_skb[NUM_TX_DESC];   /* Tx data buffers */
>>       struct napi_struct *rtl8169_napi;
>> +     struct rtl8169_rx_ring rx_ring[R8169_MAX_RX_QUEUES];
>>       unsigned int num_rx_rings;
>>       u16 cp_cmd;
>>       u16 tx_lpi_timer;
>>       u32 irq_mask;
>> +     unsigned int hw_supp_num_rx_queues;
>>       unsigned int irq_nvecs;
>>       struct clk *clk;
>>
>> @@ -764,6 +782,7 @@ struct rtl8169_private {
>>       unsigned aspm_manageable:1;
>>       unsigned dash_enabled:1;
>>       bool sfp_mode:1;
>> +     bool recheck_desc_ownbit:1;
>
>AI bots ask if this needs to be set for all chips or just some specific version.
>Also, I think this workaround should be added in a dedicated commit. For
>ease of review the introduction of struct rtl8169_rx_ring should be a code-
>reshuffling type of commit, rather than a functional change.

I will remove it from this patch and add it in a dedicated commit.

>
>>       dma_addr_t counters_phys_addr;
>>       struct rtl8169_counters *counters;
>>       struct rtl8169_tc_offsets tc_offset;