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

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Message-ID: <CAMdnO-LH0xNeMO_Y+WhSmbyNrK33zb=AtVd9ZRTObQ-n8BWR6w@mail.gmail.com>
Date: Tue, 20 Aug 2024 16:10:40 -0700
From: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
To: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.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 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
> > +#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