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SubjectRe: [PATCH v5 2/3] dmaengine: mediatek: Add MediaTek High-Speed DMA controller for MT7622 and MT7623 SoC
On Fri, Mar 02, 2018 at 02:47:51PM +0800, Sean Wang wrote:
> Hi, Vinod
>
> On Thu, 2018-03-01 at 18:26 +0530, Vinod Koul wrote:
> > On Thu, Mar 01, 2018 at 06:27:01PM +0800, Sean Wang wrote:
> > > On Thu, 2018-03-01 at 13:53 +0530, Vinod Koul wrote:
> > > > On Sun, Feb 18, 2018 at 03:08:30AM +0800, sean.wang@mediatek.com wrote:
> > > >
> > > > > @@ -0,0 +1,1054 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > // Copyright ...
> > > >
> > > > The copyright line needs to follow SPDX tag line
> > > >
> > >
> > > okay, I will make it reorder and be something like that
> > >
> > > // SPDX-License-Identifier: GPL-2.0
> > > /*
> > > * Copyright (c) 2017-2018 MediaTek Inc.
> > > * Author: Sean Wang <sean.wang@mediatek.com>
> > > *
> > > * Driver for MediaTek High-Speed DMA Controller
> > > *
> > > */
> >
> > It needs to be:
> >
> > // SPDX-License-Identifier: GPL-2.0
> > // Copyright (c) 2017-2018 MediaTek Inc.
> >
> > /*
> > * whatever else you want
> > */
> >
> > The first two lines are in C99 style comment and need to have SPDX tag and
> > Copyright info
>
> Sure, I can do it using C99 style comments at the first two lines.
>
> In addition, I'm really curious where we can find a reference to the
> rule and if it 's a strict rule for all the drivers.
>
> Because I'm considering whether I should turn other driver into using
> the same rule.

Yes that seems to be the rule now https://lkml.org/lkml/2017/11/2/715

> > > > > +#define MTK_HSDMA_USEC_POLL 20
> > > > > +#define MTK_HSDMA_TIMEOUT_POLL 200000
> > > > > +#define MTK_HSDMA_DMA_BUSWIDTHS BIT(DMA_SLAVE_BUSWIDTH_UNDEFINED)
> > > >
> > > > Undefined buswidth??
> >
> > ??
>
> Sorry for I didn't answer the question in the short time.
>
> After spending some time on a confirmation with design, it is
> DMA_SLAVE_BUSWIDTH_4_BYTES and not be configurable.

Then it should be DMA_SLAVE_BUSWIDTH_4_BYTES and not
DMA_SLAVE_BUSWIDTH_UNDEFINED...

> > > > shouldn't we check if next is in range, we can crash if we get bad value
> > > > from hardware..
> > >
> > > okay, there are checks for next with ddone bit check and null check in
> > > the corresponding descriptor as the following.
> >
> > what if you get bad next value
> >
>
> next is not hardware value. it's maintained by software which is always
> between 0 to MTK_DMA_SIZE - 1, and definitely doesn't get a bad value.
>
> > >
> > > > > + rxd = &pc->ring.rxd[next];
> >
> > resulting in bad ref here
>
> rxd is also definitely a good ref

not if next is out of range, say you read -1 or 200000?

--
~Vinod

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