Re: [PATCH net-next v2] net: stmmac: dwxgmac2: configure INTM for per-channel interrupt routing

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi

On 7/29/26 04:36, Zxyan Zhu wrote:
> The XGMAC DMA_MODE register has an INTM field (bits 13:12) that
> controls interrupt routing behavior for DMA transfer completion
> events:
> 
>   00 (default): sbd_perch_* are pulse signals, sbd_intr_o is also
>                 asserted for each completion event.
>   01:          sbd_perch_* are level signals, sbd_intr_o is NOT
>                 asserted for packet transfer completion events.
> 
> When multi-MSI is enabled, per-channel TX/RX interrupts are expected
> to arrive on their dedicated lines.  In the default INTM=00 mode,
> sbd_intr_o also fires for DMA completion events, but the multi-MSI
> handler stmmac_mac_interrupt() only processes MAC-layer events (LPI,
> PMT, timestamps) and returns IRQ_NONE for every DMA completion
> interrupt, resulting in a continuous stream of unhandled interrupts
> on the common IRQ.
> 
> Hardware verification with XGMAC and multi-MSI enabled:
> 
>   INTM=00: 5.4 million common IRQ interrupts in 3 seconds, ~1.8
>            million IRQ_NONE returns per second.
>   INTM=01: 0 common IRQ interrupts, per-channel IRQs work normally,
>            10G line rate works correctly.
> 
> Set INTM to mode 1 when multi-MSI is enabled.  This matches the
> existing GMAC4 implementation.
> 
> XGMAC multi-MSI has never worked correctly since it was introduced.
> 
> Signed-off-by: Zxyan Zhu <zxyan0222@gmail.com>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime

> ---
>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h     |  2 ++
>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c | 10 ++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> index 61b6d45a02f5..f8ab347f7b5b 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> @@ -320,6 +320,8 @@
>  /* DMA Registers */
>  #define XGMAC_DMA_MODE			0x00003000
>  #define XGMAC_SWR			BIT(0)
> +#define XGMAC_INTM_MASK			GENMASK(13, 12)
> +#define XGMAC_INTM_MODE1		0x1
>  #define XGMAC_DMA_SYSBUS_MODE		0x00003004
>  #define XGMAC_WR_OSR_LMT		GENMASK(29, 24)
>  #define XGMAC_RD_OSR_LMT		GENMASK(21, 16)
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> index 03437f1cf3df..ff83858ebc1f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> @@ -31,6 +31,16 @@ static void dwxgmac2_dma_init(void __iomem *ioaddr,
>  		value |= XGMAC_EAME;
>  
>  	writel(value, ioaddr + XGMAC_DMA_SYSBUS_MODE);
> +
> +	/*
> +	 * Route DMA interrupts to per-channel lines when multi-MSI enabled.
> +	 */
> +	if (dma_cfg->multi_msi_en) {
> +		value = readl(ioaddr + XGMAC_DMA_MODE);
> +		value = u32_replace_bits(value, XGMAC_INTM_MODE1,
> +					 XGMAC_INTM_MASK);
> +		writel(value, ioaddr + XGMAC_DMA_MODE);
> +	}
>  }
>  
>  static void dwxgmac2_dma_init_chan(struct stmmac_priv *priv,
> 
> base-commit: 1df10cef2d1e7f9f2fb7eddb67fc70d3abf101f9