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

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Message-ID: <cab82577-9979-464f-84a2-02962b1641fc@quicinc.com>
Date: Tue, 20 Aug 2024 16:12:46 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
CC: <netdev@...r.kernel.org>, <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 8/20/2024 4:10 PM, Jitendra Vegiraju wrote:
> On Thu, Aug 15, 2024 at 4:30 PM Abhishek Chauhan (ABC)
> <quic_abchauha@...cinc.com> wrote:
>>
>>
>>
>> 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?
>>
> Hi Abhishek,
> Agreed, we can make the mapping tables more generic.
> We will replace static arrays with dynamically allocated memory by
> reading the TXPDMA and RXPDMA counts from hardware.
> Thanks

That's a great idea. Thanks Jitendra. This way we do not have to hard code anything. 

>>> +#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