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Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg94H-0006eg-T2; Fri, 20 Nov 2020 16:15:25 +0000 Received: from netrider.rowland.org ([192.131.102.5]) by merlin.infradead.org with smtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kg94E-0006dc-5b for linux-arm-kernel@lists.infradead.org; Fri, 20 Nov 2020 16:15:23 +0000 Received: (qmail 619842 invoked by uid 1000); 20 Nov 2020 11:15:19 -0500 Date: Fri, 20 Nov 2020 11:15:19 -0500 From: Alan Stern To: Greg Kroah-Hartman Subject: Re: [PATCH] usb: musb: remove unused variable 'devctl' Message-ID: <20201120161519.GA619708@rowland.harvard.edu> References: <20201117082125.7619-1-min.guo@mediatek.com> <1605854930.3995.8.camel@mhfsdcap03> <1605858126.3995.14.camel@mhfsdcap03> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201120_111522_302464_7CB504F2 X-CRM114-Status: GOOD ( 28.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, chunfeng.yun@mediatek.com, linux-mediatek@lists.infradead.org, Min Guo , Matthias Brugger , Bin Liu , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 20, 2020 at 09:36:33AM +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 > > > > > > > > > > > > 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 > > > > > > --- > > > > > > 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? A better change would be - devctl = musb_readb(mbase, MUSB_DEVCTL); + (void) musb_readb(mbase, MUSB_DEVCTL); and eliminate the unused variable. Then there wouldn't be any compiler warning. Alan Stern _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel