Re: [PATCH net-next v1 4/4] net: stmmac: Use interrupt mode INTM=1 for per channel irq

[Serge Semin]

On Fri, Dec 22, 2023 at 01:44:51PM +0800, Leong Ching Swee wrote:
> From: Swee Leong Ching <leong.ching.swee@xxxxxxxxx>
> 
> Enable per DMA 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.
> 
> Signed-off-by: Teoh Ji Sheng <ji.sheng.teoh@xxxxxxxxx>
> Signed-off-by: Swee Leong Ching <leong.ching.swee@xxxxxxxxx>
> ---
>  .../net/ethernet/stmicro/stmmac/dwxgmac2.h    |  3 ++
>  .../ethernet/stmicro/stmmac/dwxgmac2_dma.c    | 32 +++++++++++--------
>  2 files changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> index 207ff1799f2c..04bf731cb7ea 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h
> @@ -346,6 +346,9 @@
>  /* DMA Registers */
>  #define XGMAC_DMA_MODE			0x00003000
>  #define XGMAC_SWR			BIT(0)
> +#define XGMAC_DMA_MODE_INTM_MASK	GENMASK(13, 12)
> +#define XGMAC_DMA_MODE_INTM_SHIFT	12
> +#define XGMAC_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 3cde695fec91..dcb9f094415d 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 &= ~XGMAC_DMA_MODE_INTM_MASK;
> +		value |= (XGMAC_DMA_MODE_INTM_MODE1 << XGMAC_DMA_MODE_INTM_SHIFT);
> +		writel(value, ioaddr + XGMAC_DMA_MODE);
> +	}
>  }
>  
>  static void dwxgmac2_dma_init_chan(struct stmmac_priv *priv,
> @@ -365,19 +372,18 @@ static int dwxgmac2_dma_interrupt(struct stmmac_priv *priv,
>  	}
>  

>  	/* TX/RX NORMAL interrupts */
> -	if (likely(intr_status & XGMAC_NIS)) {
> -		if (likely(intr_status & XGMAC_RI)) {
> -			u64_stats_update_begin(&rxq_stats->syncp);
> -			rxq_stats->rx_normal_irq_n++;
> -			u64_stats_update_end(&rxq_stats->syncp);
> -			ret |= handle_rx;
> -		}
> -		if (likely(intr_status & (XGMAC_TI | XGMAC_TBU))) {
> -			u64_stats_update_begin(&txq_stats->syncp);
> -			txq_stats->tx_normal_irq_n++;
> -			u64_stats_update_end(&txq_stats->syncp);
> -			ret |= handle_tx;
> -		}
> +	if (likely(intr_status & XGMAC_RI)) {
> +		u64_stats_update_begin(&rxq_stats->syncp);
> +		rxq_stats->rx_normal_irq_n++;
> +		u64_stats_update_end(&rxq_stats->syncp);
> +		ret |= handle_rx;
> +	}
> +
> +	if (likely(intr_status & (XGMAC_TI | XGMAC_TBU))) {
> +		u64_stats_update_begin(&txq_stats->syncp);
> +		txq_stats->tx_normal_irq_n++;
> +		u64_stats_update_end(&txq_stats->syncp);
> +		ret |= handle_tx;

Could you please clarify my comment to the original patch:

On Fri, Aug 18, 2023 at 20:10:21PM +0300, Serge Semin wrote:
> Just curious. Is this change really necessary seeing NIS IRQ is
> unmasked and it is unmasked-OR of the RI/TI/TBU flags in the
> DMA_CHx_Status register? Moreover based on the HW manual,
> DMA_CHx_Status reflects raw IRQ flags status except NIS and AIS which
> are the masked OR of the respective flags. So AFAIU NIS will be set in
> anyway if you have RI/TI/TBU IRQs enabled.

-Serge(y)

>  	}
>  
>  	/* Clear interrupts */
> -- 
> 2.34.1
> 
>