netdev - Re: [net-next v4 1/5] net: stmmac: Add HDMA mapping for dw25gmac support

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Message-ID: <2ad03012-8a10-49fc-9e80-3b91762b9cc3@quicinc.com>
Date: Thu, 15 Aug 2024 16:30:31 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: <jitendra.vegiraju@...adcom.com>, <netdev@...r.kernel.org>
CC: <alexandre.torgue@...s.st.com>, <joabreu@...opsys.com>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <mcoquelin.stm32@...il.com>,
        <bcm-kernel-feedback-list@...adcom.com>, <richardcochran@...il.com>,
        <ast@...nel.org>, <daniel@...earbox.net>, <hawk@...nel.org>,
        <john.fastabend@...il.com>, <fancer.lancer@...il.com>,
        <rmk+kernel@...linux.org.uk>, <ahalaney@...hat.com>,
        <xiaolei.wang@...driver.com>, <rohan.g.thomas@...el.com>,
        <Jianheng.Zhang@...opsys.com>, <leong.ching.swee@...el.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <bpf@...r.kernel.org>,
        <andrew@...n.ch>, <linux@...linux.org.uk>, <horms@...nel.org>,
        <florian.fainelli@...adcom.com>,
        Sagar Cheluvegowda
	<quic_scheluve@...cinc.com>
Subject: Re: [net-next v4 1/5] net: stmmac: Add HDMA mapping for dw25gmac
 support



On 8/14/2024 3:18 PM, jitendra.vegiraju@...adcom.com wrote:
> From: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
> 
> Add hdma configuration support in include/linux/stmmac.h file.
> The hdma configuration includes mapping of virtual DMAs to physical DMAs.
> Define a new data structure stmmac_hdma_cfg to provide the mapping.
> 
> Signed-off-by: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
> ---
>  include/linux/stmmac.h | 50 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> index 338991c08f00..1775bd2b7c14 100644
> --- a/include/linux/stmmac.h
> +++ b/include/linux/stmmac.h
> @@ -89,6 +89,55 @@ struct stmmac_mdio_bus_data {
>  	bool needs_reset;
>  };
>  
> +/* DW25GMAC Hyper-DMA Overview
> + * Hyper-DMA allows support for large number of Virtual DMA(VDMA)
> + * channels using a smaller set of physical DMA channels(PDMA).
> + * This is supported by the  mapping of VDMAs to Traffic Class (TC)
> + * and PDMA to TC in each traffic direction as shown below.
> + *
> + *        VDMAs            Traffic Class      PDMA
> + *       +--------+          +------+         +-----------+
> + *       |VDMA0   |--------->| TC0  |-------->|PDMA0/TXQ0 |
> + *TX     +--------+   |----->+------+         +-----------+
> + *Host=> +--------+   |      +------+         +-----------+ => MAC
> + *SW     |VDMA1   |---+      | TC1  |    +--->|PDMA1/TXQ1 |
> + *       +--------+          +------+    |    +-----------+
> + *       +--------+          +------+----+    +-----------+
> + *       |VDMA2   |--------->| TC2  |-------->|PDMA2/TXQ1 |
> + *       +--------+          +------+         +-----------+
> + *            .                 .                 .
> + *       +--------+          +------+         +-----------+
> + *       |VDMAn-1 |--------->| TCx-1|-------->|PDMAm/TXQm |
> + *       +--------+          +------+         +-----------+
> + *
> + *       +------+          +------+         +------+
> + *       |PDMA0 |--------->| TC0  |-------->|VDMA0 |
> + *       +------+   |----->+------+         +------+
> + *MAC => +------+   |      +------+         +------+
> + *RXQs   |PDMA1 |---+      | TC1  |    +--->|VDMA1 |  => Host
> + *       +------+          +------+    |    +------+
> + *            .                 .                 .
> + */
> +
> +#define STMMAC_DW25GMAC_MAX_NUM_TX_VDMA		128
> +#define STMMAC_DW25GMAC_MAX_NUM_RX_VDMA		128
> +
> +#define STMMAC_DW25GMAC_MAX_NUM_TX_PDMA		8
> +#define STMMAC_DW25GMAC_MAX_NUM_RX_PDMA		10
> +
I have a query here. 

Why do we need to hardcode the number of TX PDMA and RX PDMA to 8 an 10. On some platforms the number of supported TXPDMA and RXPDMA are 11 and 11 respectively ? 

how do we overcome this problem, do we increase the value in such case? 

> +#define STMMAC_DW25GMAC_MAX_TC			8
> +
> +/* Hyper-DMA mapping configuration
> + * Traffic Class associated with each VDMA/PDMA mapping
> + * is stored in corresponding array entry.
> + */
> +struct stmmac_hdma_cfg {
> +	u8 tvdma_tc[STMMAC_DW25GMAC_MAX_NUM_TX_VDMA];
> +	u8 rvdma_tc[STMMAC_DW25GMAC_MAX_NUM_RX_VDMA];
> +	u8 tpdma_tc[STMMAC_DW25GMAC_MAX_NUM_TX_PDMA];
> +	u8 rpdma_tc[STMMAC_DW25GMAC_MAX_NUM_RX_PDMA];
> +};
> +
>  struct stmmac_dma_cfg {
>  	int pbl;
>  	int txpbl;
> @@ -101,6 +150,7 @@ struct stmmac_dma_cfg {
>  	bool multi_msi_en;
>  	bool dche;
>  	bool atds;
> +	struct stmmac_hdma_cfg *hdma_cfg;
>  };
>  
>  #define AXI_BLEN	7