RE: [RFC/PATCH 14/18] ravb: Add rx_ring_format function for GbEthernet

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Sergey Shtylyov <s.shtylyov@omp.ru>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>
Cc: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Adam Ford <aford173@gmail.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	Biju Das <biju.das@bp.renesas.com>
Subject: RE: [RFC/PATCH 14/18] ravb: Add rx_ring_format function for GbEthernet
Date: Wed, 29 Sep 2021 07:49:47 +0000	[thread overview]
Message-ID: <TYCPR01MB59331AE19456E7FB53457C2C86A99@TYCPR01MB5933.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <c50f22d3-4741-f0a0-2664-34910d6c5ea4@omp.ru>

Hi Sergei,

> Subject: Re: [RFC/PATCH 14/18] ravb: Add rx_ring_format function for
> GbEthernet
> 
> On 9/23/21 5:08 PM, Biju Das wrote:
> 
> > This patch adds rx_ring_format function for GbEthernet found on RZ/G2L
> > SoC.
> >
> > Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> > ---
> >  drivers/net/ethernet/renesas/ravb.h      |  1 +
> >  drivers/net/ethernet/renesas/ravb_main.c | 27
> > +++++++++++++++++++++++-
> >  2 files changed, 27 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/renesas/ravb.h
> > b/drivers/net/ethernet/renesas/ravb.h
> > index 2505de5d4a28..b0e067a6a8ee 100644
> > --- a/drivers/net/ethernet/renesas/ravb.h
> > +++ b/drivers/net/ethernet/renesas/ravb.h
> > @@ -982,6 +982,7 @@ enum CSR0_BIT {
> >  #define RX_BUF_SZ	(2048 - ETH_FCS_LEN + sizeof(__sum16))
> >
> >  #define RGETH_RX_BUFF_MAX 8192
> > +#define RGETH_RX_DESC_DATA_SIZE 4080
> >
> >  struct ravb_tstamp_skb {
> >  	struct list_head list;
> > diff --git a/drivers/net/ethernet/renesas/ravb_main.c
> > b/drivers/net/ethernet/renesas/ravb_main.c
> > index 038af36141bb..ee1066fedc4a 100644
> > --- a/drivers/net/ethernet/renesas/ravb_main.c
> > +++ b/drivers/net/ethernet/renesas/ravb_main.c
> > @@ -327,7 +327,32 @@ static void ravb_ring_free(struct net_device
> > *ndev, int q)
> >
> >  static void ravb_rx_ring_format_rgeth(struct net_device *ndev, int q)
> > {
> > -	/* Place holder */
> > +	struct ravb_private *priv = netdev_priv(ndev);
> > +	struct ravb_rx_desc *rx_desc;
> > +	unsigned int rx_ring_size = sizeof(*rx_desc) * priv->num_rx_ring[q];
> > +	dma_addr_t dma_addr;
> > +	unsigned int i;
> > +
> > +	memset(priv->rgeth_rx_ring[q], 0, rx_ring_size);
> > +	/* Build RX ring buffer */
> > +	for (i = 0; i < priv->num_rx_ring[q]; i++) {
> > +		/* RX descriptor */
> > +		rx_desc = &priv->rgeth_rx_ring[q][i];
> 
>    Looks like this patch shold come bafore the patch #12 as well...

Patch#12 is timestamp related and we agreed to merge timestamp related code to gPTP support.

> 
> > +		rx_desc->ds_cc = cpu_to_le16(RGETH_RX_DESC_DATA_SIZE);
> > +		dma_addr = dma_map_single(ndev->dev.parent, priv-
> >rx_skb[q][i]->data,
> > +					  RGETH_RX_BUFF_MAX,
> 
>     Allocation buffer size more then the real data size? Does that make
> sense?

Allocated buffer is 8K and mapping buffer size is 8K. So there won't be any issues
for dma/cpu operations.

You can refer to cip kernel[1] for details
[1] https://github.com/renesas-rz/rz_linux-cip/blob/rzg2l-cip41/drivers/net/ethernet/renesas/ravb_main.c#L326

> 
> > +					  DMA_FROM_DEVICE);
> > +		/* We just set the data size to 0 for a failed mapping which
> > +		 * should prevent DMA from happening...
> > +		 */
> > +		if (dma_mapping_error(ndev->dev.parent, dma_addr))
> > +			rx_desc->ds_cc = cpu_to_le16(0);
> > +		rx_desc->dptr = cpu_to_le32(dma_addr);
> > +		rx_desc->die_dt = DT_FEMPTY;
> > +	}
> > +	rx_desc = &priv->rgeth_rx_ring[q][i];
> > +	rx_desc->dptr = cpu_to_le32((u32)priv->rx_desc_dma[q]);
> > +	rx_desc->die_dt = DT_LINKFIX; /* type */
> >  }
> >
> >  static void ravb_rx_ring_format(struct net_device *ndev, int q)
> 
> MBR, Sergey