netdev - RE: [PATCH 1/2] fsl/fman: propagate dma

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Date:   Mon, 26 Jun 2017 14:55:08 +0000
From:   Madalin-cristian Bucur <madalin.bucur@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] fsl/fman: propagate dma_ops

> -----Original Message-----
> From: geert.uytterhoeven@...il.com [mailto:geert.uytterhoeven@...il.com]
> On Behalf Of Geert Uytterhoeven
> Sent: Monday, June 26, 2017 10:49 AM
> To: Madalin-cristian Bucur <madalin.bucur@....com>
> Cc: netdev@...r.kernel.org; David S. Miller <davem@...emloft.net>;
> linuxppc-dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 1/2] fsl/fman: propagate dma_ops
> 
> Hi Madalin,
> 
> On Mon, Jun 19, 2017 at 5:04 PM, Madalin Bucur <madalin.bucur@....com>
> wrote:
> > Make sure dma_ops are set, to be later used by the Ethernet driver.
> >
> > Signed-off-by: Madalin Bucur <madalin.bucur@....com>
> > ---
> >  drivers/net/ethernet/freescale/fman/mac.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/freescale/fman/mac.c
> b/drivers/net/ethernet/freescale/fman/mac.c
> > index 0b31f85..6e67d22f 100644
> > --- a/drivers/net/ethernet/freescale/fman/mac.c
> > +++ b/drivers/net/ethernet/freescale/fman/mac.c
> > @@ -623,6 +623,8 @@ static struct platform_device
> *dpaa_eth_add_device(int fman_id,
> >                 goto no_mem;
> >         }
> >
> > +       set_dma_ops(&pdev->dev, get_dma_ops(priv->dev));
> > +
> 
> When compile-testing with f NO_DMA=y:
> 
>     drivers/net/ethernet/freescale/fman/mac.c: In function
> ‘dpaa_eth_add_device’:
>     drivers/net/ethernet/freescale/fman/mac.c:626: error: implicit
> declaration of function ‘set_dma_ops’
> 
> Reverting commit 5567e989198b5a8d fixes this regression in v4.12-rc7.
> 
> Why is this change needed?
> There's no single other call to the DMA API in this file?

We're setting here the dma_ops that are later used in the other driver/patch.
The problem is we now depend upon DMA but do not explicitly declare it:

<<Code that depends on the dma-mapping API needs to set 'depends on HAS_DMA'
in its Kconfig>>

I'll need to add this to the FMan driver Kconfig. 

> If it's really needed, can't set_dma_ops() be called from the driver that
> needs it, cfr. your other patch "[PATCH 2/2] dpaa_eth: reuse the dma_ops
> provided by the FMan MAC device"?
> 
> Thanks!
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-
> m68k.org
> 
> In personal conversations with technical people, I call myself a hacker.
> But
> when I'm talking to journalists I just say "programmer" or something like
> that.
>                                 -- Linus Torvalds

Thanks,
Madalin