Subject: Re: [PATCH v5 02/10] net: stmmac: Use interrupt mode INTM=1 for per channel irq

From: "Russell King (Oracle)" <[email-masked]>
Date: Sat, 25 Oct 2025 20:01:13 +0100

On Fri, Oct 24, 2025 at 01:49:54PM +0200, Steffen Trumtrar wrote:
> From: Teoh Ji Sheng <[email-masked]>
> 
> commit 6ccf12ae111e ("net: stmmac: use interrupt mode INTM=1
> for multi-MSI") is introduced for platform that uses MSI.
> 
> Similar approach is taken to enable per channel interrupt
> that uses shared peripheral interrupt (SPI), so only per channel
> TX and RX intr (TI/RI) are handled by TX/RX ISR without calling
> common interrupt ISR.
> 
> TX/RX NORMAL interrupts check is now decoupled, since NIS bit
> is not asserted for any TI/RI events when INTM=1.
> 
> Signed-off-by: Teoh Ji Sheng <[email-masked]>
> Signed-off-by: Steffen Trumtrar <[email-masked]>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h       |  3 +++
>  drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c   | 10 +++++++++-
>  .../net/ethernet/stmicro/stmmac/stmmac_platform.c    | 20 ++++++++++++++++++++
>  include/linux/stmmac.h                               |  2 ++
>  4 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> index 0d408ee17f337..64b533207e4a6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> @@ -326,6 +326,9 @@
>  /* DMA Registers */
>  #define XGMAC_DMA_MODE			0x00003000
>  #define XGMAC_SWR			BIT(0)
> +#define DMA_MODE_INTM_MASK		GENMASK(13, 12)
> +#define DMA_MODE_INTM_SHIFT		12
> +#define DMA_MODE_INTM_MODE1		0x1
>  #define XGMAC_DMA_SYSBUS_MODE		0x00003004
>  #define XGMAC_WR_OSR_LMT		GENMASK(29, 24)
>  #define XGMAC_WR_OSR_LMT_SHIFT		24
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> index 4d6bb995d8d84..1e9ee1f10f0ef 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c
> @@ -31,6 +31,13 @@ static void dwxgmac2_dma_init(void __iomem *ioaddr,
>  		value |= XGMAC_EAME;
>  
>  	writel(value, ioaddr + XGMAC_DMA_SYSBUS_MODE);
> +
> +	if (dma_cfg->multi_irq_en) {
> +		value = readl(ioaddr + XGMAC_DMA_MODE);
> +		value &= ~DMA_MODE_INTM_MASK;
> +		value |= (DMA_MODE_INTM_MODE1 << DMA_MODE_INTM_SHIFT);

No need for these parens. What is on the right hand side of |= is its
own expression and can't be interpreted any other way.

> +		writel(value, ioaddr + XGMAC_DMA_MODE);
> +	}
>  }
>  
>  static void dwxgmac2_dma_init_chan(struct stmmac_priv *priv,
> @@ -359,13 +366,14 @@ static int dwxgmac2_dma_interrupt(struct stmmac_priv *priv,
>  		}
>  	}
>  
> -	/* TX/RX NORMAL interrupts */
> +	/* RX NORMAL interrupts */
>  	if (likely(intr_status & XGMAC_RI)) {
>  		u64_stats_update_begin(&stats->syncp);
>  		u64_stats_inc(&stats->rx_normal_irq_n[chan]);
>  		u64_stats_update_end(&stats->syncp);
>  		ret |= handle_rx;
>  	}
> +	/* TX NORMAL interrupts */
>  	if (likely(intr_status & (XGMAC_TI | XGMAC_TBU))) {
>  		u64_stats_update_begin(&stats->syncp);
>  		u64_stats_inc(&stats->tx_normal_irq_n[chan]);
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 27bcaae07a7f2..cfa82b8e04b94 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -607,6 +607,8 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  	dma_cfg->fixed_burst = of_property_read_bool(np, "snps,fixed-burst");
>  	dma_cfg->mixed_burst = of_property_read_bool(np, "snps,mixed-burst");
>  
> +	dma_cfg->multi_irq_en = of_property_read_bool(np, "snps,multi-irq-en");
> +
>  	plat->force_thresh_dma_mode = of_property_read_bool(np, "snps,force_thresh_dma_mode");
>  	if (plat->force_thresh_dma_mode && plat->force_sf_dma_mode) {
>  		plat->force_sf_dma_mode = 0;
> @@ -737,6 +739,8 @@ EXPORT_SYMBOL_GPL(stmmac_pltfr_find_clk);
>  int stmmac_get_platform_resources(struct platform_device *pdev,
>  				  struct stmmac_resources *stmmac_res)
>  {
> +	char irq_name[11];
> +	int i;
>  	memset(stmmac_res, 0, sizeof(*stmmac_res));

We normally want to see a blank line between local variable declarations
and code.

>  
>  	/* Get IRQ information early to have an ability to ask for deferred
> @@ -746,6 +750,22 @@ int stmmac_get_platform_resources(struct platform_device *pdev,
>  	if (stmmac_res->irq < 0)
>  		return stmmac_res->irq;
>  
> +	/* For RX Channel */
> +	for (i = 0; i < MTL_MAX_RX_QUEUES; i++) {
> +		sprintf(irq_name, "%s%d", "macirq_rx", i);
> +		stmmac_res->rx_irq[i] = platform_get_irq_byname(pdev, irq_name);
> +		if (stmmac_res->rx_irq[i] < 0)
> +			break;
> +	}
> +
> +	/* For TX Channel */
> +	for (i = 0; i < MTL_MAX_TX_QUEUES; i++) {
> +		sprintf(irq_name, "%s%d", "macirq_tx", i);
> +		stmmac_res->tx_irq[i] = platform_get_irq_byname(pdev, irq_name);
> +			if (stmmac_res->tx_irq[i] < 0)
> +				break;
> +	}
> +

It looks like multi-irq is a dwxgmac2 thing, should this be conditional
on (a) multi_irq_en being set, and (b) should parsing multi_irq_en be
conditional on dwxgmac2, (c) should the binding only allow
snps,multi-irq-en if a dwxgmac2 compatible is indicated?

-- 
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