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Message-ID: <977edc1fd4d33b6bf95198ccf6ec6946a84f3b58.camel@calian.com>
Date:   Fri, 4 Mar 2022 23:01:19 +0000
From:   Robert Hancock <robert.hancock@...ian.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "radhey.shyam.pandey@...inx.com" <radhey.shyam.pandey@...inx.com>,
        "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH net-next 7/7] net: axienet: add coalesce timer ethtool
 configuration

On Fri, 2022-03-04 at 16:42 -0600, Robert Hancock wrote:
> Add the ability to configure the RX/TX coalesce timer with ethtool.
> Change default setting to scale with the clock rate rather than being a
> fixed number of clock cycles.
> 
> Signed-off-by: Robert Hancock <robert.hancock@...ian.com>
> ---
>  drivers/net/ethernet/xilinx/xilinx_axienet.h  |  8 +--
>  .../net/ethernet/xilinx/xilinx_axienet_main.c | 49 +++++++++++++++----
>  2 files changed, 44 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h
> b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> index 6f0f13b4fb1a..f6d365cb57de 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> @@ -119,11 +119,11 @@
>  #define XAXIDMA_IRQ_ERROR_MASK		0x00004000 /* Error interrupt
> */
>  #define XAXIDMA_IRQ_ALL_MASK		0x00007000 /* All interrupts */
>  
> -/* Default TX/RX Threshold and waitbound values for SGDMA mode */
> +/* Default TX/RX Threshold and delay timer values for SGDMA mode */
>  #define XAXIDMA_DFT_TX_THRESHOLD	24
> -#define XAXIDMA_DFT_TX_WAITBOUND	254
> +#define XAXIDMA_DFT_TX_USEC		50
>  #define XAXIDMA_DFT_RX_THRESHOLD	1
> -#define XAXIDMA_DFT_RX_WAITBOUND	254
> +#define XAXIDMA_DFT_RX_USEC		50
>  
>  #define XAXIDMA_BD_CTRL_TXSOF_MASK	0x08000000 /* First tx packet */
>  #define XAXIDMA_BD_CTRL_TXEOF_MASK	0x04000000 /* Last tx packet */
> @@ -482,7 +482,9 @@ struct axienet_local {
>  	int csum_offload_on_rx_path;
>  
>  	u32 coalesce_count_rx;
> +	u32 coalesce_usec_rx;
>  	u32 coalesce_count_tx;
> +	u32 coalesce_usec_tx;
>  };
>  
>  /**
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index 828ab7a81797..8d908a5feea2 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -226,6 +226,28 @@ static void axienet_dma_bd_release(struct net_device
> *ndev)
>  			  lp->rx_bd_p);
>  }
>  
> +/**
> + * axienet_usec_to_timer - Calculate IRQ delay timer value
> + * @lp:		Pointer to the axienet_local structure
> + * @coalesce_usec: Microseconds to convert into timer value
> + */
> +static u32 axienet_usec_to_timer(struct axienet_local *lp, u32
> coalesce_usec)
> +{
> +	u32 result;
> +	u64 clk_rate = 125000000; /* arbitrary guess if no clock rate set */
> +
> +	if (lp->axi_clk)
> +		clk_rate = clk_get_rate(lp->axi_clk);
> +
> +	/* 1 Timeout Interval = 125 * (clock period of SG clock) */
> +	result = DIV_ROUND_CLOSEST((u64)coalesce_usec * clk_rate,
> +				   (u64)125000000);

Looks like there's a compile error on 32-bit here. Will fix..

> +	if (result > 255)
> +		result = 255;
> +
> +	return result;
> +}
> +
>  /**
>   * axienet_dma_start - Set up DMA registers and start DMA operation
>   * @lp:		Pointer to the axienet_local structure
> @@ -241,7 +263,8 @@ static void axienet_dma_start(struct axienet_local *lp)
>  	 * the first RX packet. Otherwise leave at 0 to disable delay
> interrupt.
>  	 */
>  	if (lp->coalesce_count_rx > 1)
> -		lp->rx_dma_cr |= (XAXIDMA_DFT_RX_WAITBOUND <<
> XAXIDMA_DELAY_SHIFT) |
> +		lp->rx_dma_cr |= (axienet_usec_to_timer(lp, lp-
> >coalesce_usec_rx)
> +					<< XAXIDMA_DELAY_SHIFT) |
>  				 XAXIDMA_IRQ_DELAY_MASK;
>  	axienet_dma_out32(lp, XAXIDMA_RX_CR_OFFSET, lp->rx_dma_cr);
>  
> @@ -252,7 +275,8 @@ static void axienet_dma_start(struct axienet_local *lp)
>  	 * the first TX packet. Otherwise leave at 0 to disable delay
> interrupt.
>  	 */
>  	if (lp->coalesce_count_tx > 1)
> -		tx_cr |= (XAXIDMA_DFT_TX_WAITBOUND << XAXIDMA_DELAY_SHIFT) |
> +		tx_cr |= (axienet_usec_to_timer(lp, lp->coalesce_usec_tx)
> +				<< XAXIDMA_DELAY_SHIFT) |
>  			 XAXIDMA_IRQ_DELAY_MASK;
>  	axienet_dma_out32(lp, XAXIDMA_TX_CR_OFFSET, tx_cr);
>  
> @@ -1487,14 +1511,12 @@ axienet_ethtools_get_coalesce(struct net_device
> *ndev,
>  			      struct kernel_ethtool_coalesce *kernel_coal,
>  			      struct netlink_ext_ack *extack)
>  {
> -	u32 regval = 0;
>  	struct axienet_local *lp = netdev_priv(ndev);
> -	regval = axienet_dma_in32(lp, XAXIDMA_RX_CR_OFFSET);
> -	ecoalesce->rx_max_coalesced_frames = (regval & XAXIDMA_COALESCE_MASK)
> -					     >> XAXIDMA_COALESCE_SHIFT;
> -	regval = axienet_dma_in32(lp, XAXIDMA_TX_CR_OFFSET);
> -	ecoalesce->tx_max_coalesced_frames = (regval & XAXIDMA_COALESCE_MASK)
> -					     >> XAXIDMA_COALESCE_SHIFT;
> +
> +	ecoalesce->rx_max_coalesced_frames = lp->coalesce_count_rx;
> +	ecoalesce->rx_coalesce_usecs = lp->coalesce_usec_rx;
> +	ecoalesce->tx_max_coalesced_frames = lp->coalesce_count_tx;
> +	ecoalesce->tx_coalesce_usecs = lp->coalesce_usec_tx;
>  	return 0;
>  }
>  
> @@ -1527,8 +1549,12 @@ axienet_ethtools_set_coalesce(struct net_device *ndev,
>  
>  	if (ecoalesce->rx_max_coalesced_frames)
>  		lp->coalesce_count_rx = ecoalesce->rx_max_coalesced_frames;
> +	if (ecoalesce->rx_coalesce_usecs)
> +		lp->coalesce_usec_rx = ecoalesce->rx_coalesce_usecs;
>  	if (ecoalesce->tx_max_coalesced_frames)
>  		lp->coalesce_count_tx = ecoalesce->tx_max_coalesced_frames;
> +	if (ecoalesce->tx_coalesce_usecs)
> +		lp->coalesce_usec_tx = ecoalesce->tx_coalesce_usecs;
>  
>  	return 0;
>  }
> @@ -1559,7 +1585,8 @@ static int axienet_ethtools_nway_reset(struct
> net_device *dev)
>  }
>  
>  static const struct ethtool_ops axienet_ethtool_ops = {
> -	.supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES,
> +	.supported_coalesce_params = ETHTOOL_COALESCE_MAX_FRAMES |
> +				     ETHTOOL_COALESCE_USECS,
>  	.get_drvinfo    = axienet_ethtools_get_drvinfo,
>  	.get_regs_len   = axienet_ethtools_get_regs_len,
>  	.get_regs       = axienet_ethtools_get_regs,
> @@ -2046,7 +2073,9 @@ static int axienet_probe(struct platform_device *pdev)
>  	}
>  
>  	lp->coalesce_count_rx = XAXIDMA_DFT_RX_THRESHOLD;
> +	lp->coalesce_usec_rx = XAXIDMA_DFT_RX_USEC;
>  	lp->coalesce_count_tx = XAXIDMA_DFT_TX_THRESHOLD;
> +	lp->coalesce_usec_tx = XAXIDMA_DFT_TX_USEC;
>  
>  	/* Reset core now that clocks are enabled, prior to accessing MDIO */
>  	ret = __axienet_device_reset(lp);

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