Re: [RFC PATCH net-next v2 3/6] net: xilinx: axienet: Combine CR calculation

["Nelson, Shannon" <shannon.nelson@amd.com>]

On 9/9/2024 4:52 PM, Sean Anderson wrote:
> 
> Combine the common parts of the CR calculations for better code reuse.
> While we're at it, simplify the code a bit.
> 
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
> ---
> 
> Changes in v2:
> - Split off from runtime coalesce modification support
> 
>   drivers/net/ethernet/xilinx/xilinx_axienet.h  |  2 -
>   .../net/ethernet/xilinx/xilinx_axienet_main.c | 69 ++++++++++---------
>   2 files changed, 35 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> index 5c0a21ef96a4..c43ce8f7590c 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> @@ -112,8 +112,6 @@
>   #define XAXIDMA_DELAY_MASK             ((u32)0xFF000000) /* Delay timeout counter */
>   #define XAXIDMA_COALESCE_MASK          ((u32)0x00FF0000) /* Coalesce counter */
> 
> -#define XAXIDMA_DELAY_SHIFT            24
> -
>   #define XAXIDMA_IRQ_IOC_MASK           0x00001000 /* Completion intr */
>   #define XAXIDMA_IRQ_DELAY_MASK         0x00002000 /* Delay interrupt */
>   #define XAXIDMA_IRQ_ERROR_MASK         0x00004000 /* Error interrupt */
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index bc987f7ca1ea..bff94d378b9f 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -224,22 +224,41 @@ static void axienet_dma_bd_release(struct net_device *ndev)
>   }
> 
>   /**
> - * axienet_usec_to_timer - Calculate IRQ delay timer value
> - * @lp:                Pointer to the axienet_local structure
> - * @coalesce_usec: Microseconds to convert into timer value
> + * axienet_calc_cr() - Calculate control register value
> + * @lp: Device private data
> + * @coalesce_count: Number of completions before an interrupt
> + * @coalesce_usec: Microseconds after the last completion before an interrupt

nit: The comments should match the actual parameter names
sln

> + *
> + * Calculate a control register value based on the coalescing settings. The
> + * run/stop bit is not set.
>    */
> -static u32 axienet_usec_to_timer(struct axienet_local *lp, u32 coalesce_usec)
> +static u32 axienet_calc_cr(struct axienet_local *lp, u32 count, u32 usec)
>   {
> -       u32 result;
> -       u64 clk_rate = 125000000; /* arbitrary guess if no clock rate set */
> +       u32 cr;
> 
> -       if (lp->axi_clk)
> -               clk_rate = clk_get_rate(lp->axi_clk);
> +       count = min(count, FIELD_MAX(XAXIDMA_COALESCE_MASK));
> +       cr = FIELD_PREP(XAXIDMA_COALESCE_MASK, count) | XAXIDMA_IRQ_IOC_MASK |
> +            XAXIDMA_IRQ_ERROR_MASK;
> +       /* Only set interrupt delay timer if not generating an interrupt on
> +        * the first packet. Otherwise leave at 0 to disable delay interrupt.
> +        */
> +       if (count > 1) {
> +               u64 clk_rate = 125000000; /* arbitrary guess if no clock rate set */
> +               u32 timer;
> 
> -       /* 1 Timeout Interval = 125 * (clock period of SG clock) */
> -       result = DIV64_U64_ROUND_CLOSEST((u64)coalesce_usec * clk_rate,
> -                                        XAXIDMA_DELAY_SCALE);
> -       return min(result, FIELD_MAX(XAXIDMA_DELAY_MASK));
> +               if (lp->axi_clk)
> +                       clk_rate = clk_get_rate(lp->axi_clk);
> +
> +               /* 1 Timeout Interval = 125 * (clock period of SG clock) */
> +               timer = DIV64_U64_ROUND_CLOSEST((u64)usec * clk_rate,
> +                                               XAXIDMA_DELAY_SCALE);
> +
> +               timer = min(timer, FIELD_MAX(XAXIDMA_DELAY_MASK));
> +               cr |= FIELD_PREP(XAXIDMA_DELAY_MASK, timer) |
> +                     XAXIDMA_IRQ_DELAY_MASK;
> +       }
> +
> +       return cr;
>   }
> 
>   /**
> @@ -249,31 +268,13 @@ static u32 axienet_usec_to_timer(struct axienet_local *lp, u32 coalesce_usec)
>   static void axienet_dma_start(struct axienet_local *lp)
>   {
>          /* Start updating the Rx channel control register */
> -       lp->rx_dma_cr = FIELD_PREP(XAXIDMA_COALESCE_MASK,
> -                                  min(lp->coalesce_count_rx,
> -                                      FIELD_MAX(XAXIDMA_COALESCE_MASK))) |
> -                       XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_ERROR_MASK;
> -       /* Only set interrupt delay timer if not generating an interrupt on
> -        * the first RX packet. Otherwise leave at 0 to disable delay interrupt.
> -        */
> -       if (lp->coalesce_count_rx > 1)
> -               lp->rx_dma_cr |= (axienet_usec_to_timer(lp, lp->coalesce_usec_rx)
> -                                       << XAXIDMA_DELAY_SHIFT) |
> -                                XAXIDMA_IRQ_DELAY_MASK;
> +       lp->rx_dma_cr = axienet_calc_cr(lp, lp->coalesce_count_rx,
> +                                       lp->coalesce_usec_rx);
>          axienet_dma_out32(lp, XAXIDMA_RX_CR_OFFSET, lp->rx_dma_cr);
> 
>          /* Start updating the Tx channel control register */
> -       lp->tx_dma_cr = FIELD_PREP(XAXIDMA_COALESCE_MASK,
> -                                  min(lp->coalesce_count_tx,
> -                                      FIELD_MAX(XAXIDMA_COALESCE_MASK))) |
> -                       XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_ERROR_MASK;
> -       /* Only set interrupt delay timer if not generating an interrupt on
> -        * the first TX packet. Otherwise leave at 0 to disable delay interrupt.
> -        */
> -       if (lp->coalesce_count_tx > 1)
> -               lp->tx_dma_cr |= (axienet_usec_to_timer(lp, lp->coalesce_usec_tx)
> -                                       << XAXIDMA_DELAY_SHIFT) |
> -                                XAXIDMA_IRQ_DELAY_MASK;
> +       lp->tx_dma_cr = axienet_calc_cr(lp, lp->coalesce_count_tx,
> +                                       lp->coalesce_usec_tx);
>          axienet_dma_out32(lp, XAXIDMA_TX_CR_OFFSET, lp->tx_dma_cr);
> 
>          /* Populate the tail pointer and bring the Rx Axi DMA engine out of
> --
> 2.35.1.1320.gc452695387.dirty
> 
>