From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Min Guo <min.guo@mediatek.com>
Cc: Bin Liu <b-liu@ti.com>, Matthias Brugger <matthias.bgg@gmail.com>,
chunfeng.yun@mediatek.com, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org
Subject: Re: [PATCH] usb: musb: remove unused variable 'devctl'
Date: Fri, 20 Nov 2020 10:20:58 +0100 [thread overview]
Message-ID: <X7eKetkCN+Z3meyB@kroah.com> (raw)
In-Reply-To: <1605862935.3995.20.camel@mhfsdcap03>
On Fri, Nov 20, 2020 at 05:02:15PM +0800, Min Guo wrote:
> On Fri, 2020-11-20 at 09:36 +0100, Greg Kroah-Hartman wrote:
> > On Fri, Nov 20, 2020 at 03:42:06PM +0800, Min Guo wrote:
> > > On Fri, 2020-11-20 at 07:54 +0100, Greg Kroah-Hartman wrote:
> > > > On Fri, Nov 20, 2020 at 02:48:50PM +0800, Min Guo wrote:
> > > > > Hi greg k-h:
> > > > > On Wed, 2020-11-18 at 12:48 +0100, Greg Kroah-Hartman wrote:
> > > > > > On Tue, Nov 17, 2020 at 04:21:25PM +0800, min.guo@mediatek.com wrote:
> > > > > > > From: Min Guo <min.guo@mediatek.com>
> > > > > > >
> > > > > > > Remove unused 'devctl' variable to fix compile warnings:
> > > > > > >
> > > > > > > drivers/usb/musb/musbhsdma.c: In function 'dma_controller_irq':
> > > > > > > drivers/usb/musb/musbhsdma.c:324:8: warning: variable 'devctl' set
> > > > > > > but not used [-Wunused-but-set-variable]
> > > > > > >
> > > > > > > Signed-off-by: Min Guo <min.guo@mediatek.com>
> > > > > > > ---
> > > > > > > drivers/usb/musb/musbhsdma.c | 4 ----
> > > > > > > 1 file changed, 4 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
> > > > > > > index 0aacfc8be5a1..7acd1635850d 100644
> > > > > > > --- a/drivers/usb/musb/musbhsdma.c
> > > > > > > +++ b/drivers/usb/musb/musbhsdma.c
> > > > > > > @@ -321,8 +321,6 @@ irqreturn_t dma_controller_irq(int irq, void *private_data)
> > > > > > > musb_channel->channel.status =
> > > > > > > MUSB_DMA_STATUS_BUS_ABORT;
> > > > > > > } else {
> > > > > > > - u8 devctl;
> > > > > > > -
> > > > > > > addr = musb_read_hsdma_addr(mbase,
> > > > > > > bchannel);
> > > > > > > channel->actual_len = addr
> > > > > > > @@ -336,8 +334,6 @@ irqreturn_t dma_controller_irq(int irq, void *private_data)
> > > > > > > < musb_channel->len) ?
> > > > > > > "=> reconfig 0" : "=> complete");
> > > > > > >
> > > > > > > - devctl = musb_readb(mbase, MUSB_DEVCTL);
> > > > > >
> > > > > > Are you sure that the hardware does not require this read to complete
> > > > > > the command? Lots of hardware is that way, so be very careful about
> > > > > > this. Did you test it?
> > > > >
> > > > > I have tested this patch on Mediatek's platform, and not sure if it
> > > > > will affect other vendors' platforms.
> > > > >
> > > > > Dear Bin:
> > > > >
> > > > > Does this patch will affect other vendors' platforms?
> > > >
> > > > The hardware specs will answer this question, what do they say about
> > > > this read?
> > >
> > > Sorry, I didn't seen the comment on the hardware specs indicate that
> > > devctl register needs to read once to take effect.
> >
> > Perhaps you might want to add a comment here so that people will not
> > keep making this same mistake when they run auto-checkers on the
> > codebase?
>
> Sorry for confused you, I searched the hardware specs, but did not find
> the special description of the register devctl indicating that it needs
> to be read out before the hardware can work.
If this is a PCI device, that is implied as that is how all PCI devices
work, right?
What is the problem that is fixed by removing this read?
thanks,
greg k-h
next prev parent reply other threads:[~2020-11-20 9:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 8:21 [PATCH] usb: musb: remove unused variable 'devctl' min.guo
2020-11-18 11:48 ` Greg Kroah-Hartman
2020-11-20 6:48 ` Min Guo
2020-11-20 6:54 ` Greg Kroah-Hartman
2020-11-20 7:42 ` Min Guo
2020-11-20 8:36 ` Greg Kroah-Hartman
2020-11-20 9:02 ` Min Guo
2020-11-20 9:20 ` Greg Kroah-Hartman [this message]
2020-11-20 16:15 ` Alan Stern
2020-11-20 16:32 ` Greg Kroah-Hartman
2020-11-20 16:37 ` Alan Stern
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