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Message-ID: <491180c3-680d-41cf-a799-d1099542882c@amd.com>
Date: Mon, 9 Sep 2024 18:32:21 -0700
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Sean Anderson <sean.anderson@...ux.dev>,
"David S . Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Radhey Shyam Pandey <radhey.shyam.pandey@....com>, netdev@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org, Michal Simek
<michal.simek@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next v2 3/6] net: xilinx: axienet: Combine CR
calculation
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@...ux.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
>
>
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