netdev - RE: [PATCH] dpaa_eth: use correct device for DMA mapping API

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Date:   Tue, 11 Jul 2017 14:22:14 +0000
From:   Madalin-cristian Bucur <madalin.bucur@....com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        "David S . Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "Camelia Alexandra Groza" <camelia.groza@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] dpaa_eth: use correct device for DMA mapping API

> -----Original Message-----
> From: arndbergmann@...il.com [mailto:arndbergmann@...il.com] On Behalf Of
> Arnd Bergmann
> Subject: Re: [PATCH] dpaa_eth: use correct device for DMA mapping API
> 
> On Tue, Jul 11, 2017 at 10:50 AM, Madalin-cristian Bucur
> <madalin.bucur@....com> wrote:
> 
> > Hi Arnd,
> >
> > Thanks for looking into this, I've tested your fix, it seems to need
> more work:
> >
> > [    0.894968]  platform: DMA map failed
> > [    0.898627]  platform: DMA map failed
> > [    0.902288]  platform: DMA map failed
> > [    0.905947]  platform: DMA map failed
> > [    0.909606]  platform: DMA map failed
> > [    0.913265]  platform: DMA map failed
> 
> I see: the assignment ended up after the first use, so ->dev was still
> NULL here.
> 
> This should fix the problem you saw here:
> 
> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> index f7b0b928cd53..988c0212ce7e 100644
> --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> @@ -2650,6 +2650,8 @@ static int dpaa_eth_probe(struct platform_device
> *pdev)
>   for (i = 0; i < DPAA_BPS_NUM; i++) {
>   int err;
> 
> + /* DMA operations are done on the platform-provided device */
> + dpaa_bps[i]->dev = dev->parent;
>   dpaa_bps[i] = dpaa_bp_alloc(dev);

Your new change de-references dpaa_bps[i] before it is set, this won't work either.

>   if (IS_ERR(dpaa_bps[i]))
>   return PTR_ERR(dpaa_bps[i]);
> @@ -2657,8 +2659,6 @@ static int dpaa_eth_probe(struct platform_device
> *pdev)
>   dpaa_bps[i]->raw_size = bpool_buffer_raw_size(i, DPAA_BPS_NUM);
>   /* avoid runtime computations by keeping the usable size here */
>   dpaa_bps[i]->size = dpaa_bp_size(dpaa_bps[i]->raw_size);
> - /* DMA operations are done on the platform-provided device */
> - dpaa_bps[i]->dev = dev->parent;
> 
>   err = dpaa_bp_alloc_pool(dpaa_bps[i]);
>   if (err < 0) {
> 
> > @@ -2806,7 +2799,6 @@ static int dpaa_eth_probe(struct platform_device
> *pdev)
> >                 dpaa_bps_free(priv);
> >  bp_create_failed:
> >  fq_probe_failed:
> > -dev_mask_failed:
> >  mac_probe_failed:
> >                 dev_set_drvdata(dev, NULL);
> >                 free_netdev(net_dev);
> >
> > I'll try to address your concern about performing the DMA mapping on a
> different
> > device than the one set up by the platform code.
> 
> Thanks!
> 
>      Arnd