netdev - RE: [PATCH] net: fec: set dma_coherent

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Date:   Wed, 28 Mar 2018 03:04:17 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>
CC:     netdev <netdev@...r.kernel.org>,
        Linux/m68k <linux-m68k@...r.kernel.org>
Subject: RE: [PATCH] net: fec: set dma_coherent_mask

From: Geert Uytterhoeven <geert@...ux-m68k.org> Sent: 2018年3月27日 20:59
> Hi Greg,
> 
> On Mon, Mar 26, 2018 at 3:36 PM, Greg Ungerer <gerg@...ux-m68k.org> wrote:
> > As of commit 205e1b7f51e4 ("dma-mapping: warn when there is no
> > coherent_dma_mask") the Freescale FEC driver is issuing the following
> > warning on driver initialization on ColdFire systems:
> >
> > WARNING: CPU: 0 PID: 1 at ./include/linux/dma-mapping.h:516 0x40159e20
> > Modules linked in:
> > CPU: 0 PID: 1 Comm: swapper Not tainted 4.16.0-rc7-dirty #4 Stack from
> > 41833dd8:
> >         41833dd8 40259c53 40025534 40279e26 00000003 00000000
> 4004e514 41827000
> >         400255de 40244e42 00000204 40159e20 00000009 00000000
> 00000000 4024531d
> >         40159e20 40244e42 00000204 00000000 00000000 00000000
> 00000007 00000000
> >         00000000 40279e26 4028d040 40226576 4003ae88 40279e26
> 418273f6 41833ef8
> >         7fffffff 418273f2 41867028 4003c9a2 4180ac6c 00000004 41833f8c
> 4013e71c
> >         40279e1c 40279e26 40226c16 4013ced2 40279e26 40279e58
> 4028d040
> > 00000000 Call Trace:
> >         [<40025534>] 0x40025534
> >  [<4004e514>] 0x4004e514
> >  [<400255de>] 0x400255de
> >  [<40159e20>] 0x40159e20
> >  [<40159e20>] 0x40159e20
> >
> > It is not fatal, the driver and the system continue to function normally.
> >
> > As per the warning the coherent_dma_mask is not set on this device.
> > There is nothing special about the DMA memory coherency on this
> > hardware so we can just set the mask to 32bits during probe.
> >
> > Signed-off-by: Greg Ungerer <gerg@...ux-m68k.org>
> 
> Thanks for your patch!
> 
> > ---
> >  drivers/net/ethernet/freescale/fec_main.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > Is this the best way to handle this problem?
> > Comments welcome...
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_main.c
> > b/drivers/net/ethernet/freescale/fec_main.c
> > index d4604bc..3cb130a 100644
> > --- a/drivers/net/ethernet/freescale/fec_main.c
> > +++ b/drivers/net/ethernet/freescale/fec_main.c
> > @@ -2702,6 +2702,8 @@ static int fec_enet_alloc_queue(struct net_device
> *ndev)
> >         int ret = 0;
> >         struct fec_enet_priv_tx_q *txq;
> >
> > +       dma_set_coherent_mask(&fep->pdev->dev, DMA_BIT_MASK(32));
> > +
> >         for (i = 0; i < fep->num_tx_queues; i++) {
> >                 txq = kzalloc(sizeof(*txq), GFP_KERNEL);
> >                 if (!txq) {
> 
> As per your other email, this does not trigger on iMX systems using DT.
> Hence I'm wondering if the Coldfire platform code shouldn't just do the same what
> drivers/of/device.c does, cfr.
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.s
> pinics.net%2Flists%2Flinux-m68k%2Fmsg10929.html&data=02%7C01%7Cfugan
> g.duan%40nxp.com%7C3db2dbadf1154965370608d593e294b2%7C686ea1d3
> bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636577523756185995&sdata=bsO
> F%2BnSeXTP7C%2F55JLO3Pv8YybPahMaZDyqB16f9ySA%3D&reserved=0?
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
It is better to use of_dma_configure(&pdev->dev, np), it iommu support, device also can allocate memory from 64bit space.

Andy