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

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Date:   Wed, 28 Mar 2018 07:15:05 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Greg Ungerer <gerg@...ux-m68k.org>,
        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28日 15:07
> Hi Andy,
> 
> On Wed, Mar 28, 2018 at 5:04 AM, Andy Duan <fugang.duan@....com> wrote:
> > From: Geert Uytterhoeven <geert@...ux-m68k.org> Sent: 2018年3月27日
> 20:59
> >> 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%2Fww
> >> w.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.
> 
> At first sight, it indeed looks like of_dma_configure() would do the right thing,
> even on platforms without DT like Coldfire.
> 
> Unfortunately of_dma_configure() is replaced by a dummy if !CONFIG_OF.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
Yes, it only supports DT.

Andy