netdev - RE: [PATCH] qlcnic: dma address align check

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Date:	Tue, 26 Oct 2010 05:04:18 -0500
From:	Amit Salecha <amit.salecha@...gic.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ameen Rahman <ameen.rahman@...gic.com>,
	Anirban Chakraborty <anirban.chakraborty@...gic.com>
Subject: RE: [PATCH] qlcnic: dma address align check



> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> Sent: Tuesday, October 26, 2010 3:25 PM
> To: Amit Salecha
> Cc: davem@...emloft.net; netdev@...r.kernel.org; Ameen Rahman; Anirban
> Chakraborty
> Subject: Re: [PATCH] qlcnic: dma address align check
> 
> Le mardi 26 octobre 2010 à 02:38 -0700, Amit Kumar Salecha a écrit :
> > Device requires tx_hw_cosnumer to be 64 byte aligned.
> > Tx desc size is 64 byte, alloc tx_hw_consumer with tx desc.
> >
> > Signed-off-by: Amit Kumar Salecha <amit.salecha@...gic.com>
> > ---
> >  drivers/net/qlcnic/qlcnic_ctx.c |   35 +++++++++++++++--------------
> ------
> >  1 files changed, 15 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/net/qlcnic/qlcnic_ctx.c
> b/drivers/net/qlcnic/qlcnic_ctx.c
> > index 1cdc05d..21c9c28 100644
> > --- a/drivers/net/qlcnic/qlcnic_ctx.c
> > +++ b/drivers/net/qlcnic/qlcnic_ctx.c
> > @@ -418,18 +418,9 @@ int qlcnic_alloc_hw_resources(struct
> qlcnic_adapter *adapter)
> >  	recv_ctx = &adapter->recv_ctx;
> >  	tx_ring = adapter->tx_ring;
> >
> > -	tx_ring->hw_consumer = (__le32 *)pci_alloc_consistent(pdev,
> sizeof(u32),
> > -						&tx_ring->hw_cons_phys_addr);
> > -	if (tx_ring->hw_consumer == NULL) {
> > -		dev_err(&pdev->dev, "failed to allocate tx consumer\n");
> > -		return -ENOMEM;
> > -	}
> > -	*(tx_ring->hw_consumer) = 0;
> > -
> >  	/* cmd desc ring */
> > -	addr = pci_alloc_consistent(pdev, TX_DESC_RINGSIZE(tx_ring),
> > -			&tx_ring->phys_addr);
> > -
> > +	addr = pci_alloc_consistent(pdev, TX_DESC_RINGSIZE(tx_ring) +
> > +			sizeof(u32), &tx_ring->phys_addr);
> 
> Wont this use twice memory than before, due to power-of-two
> allocations ?
> 
> Allocating 65536 + 4 bytes gives you 131072 bytes.
>
Is it ? I am not aware about such calculation.
Is pci_alloc_consistent guarantee to give PAGE align dma address ?

-Amit