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([2a00:1fa0:44aa:1e8:bf33:c8db:a3e2:c358]) by smtp.gmail.com with ESMTPSA id k28sm983027lfj.48.2020.11.24.03.45.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Nov 2020 03:45:02 -0800 (PST) Subject: Re: [PATCH v3] usb: musb: remove unused variable 'devctl' From: Sergei Shtylyov To: min.guo@mediatek.com, Bin Liu Cc: Greg Kroah-Hartman , Alan Stern , Matthias Brugger , 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 References: <20201124084955.30270-1-min.guo@mediatek.com> Message-ID: Date: Tue, 24 Nov 2020 14:45:01 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/24/20 12:13 PM, Sergei Shtylyov 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 >> --- >> changes in v3 >> suggested by Greg Kroah-Hartman: >> Add a comment. >> >> changes in v2 >> suggested by Alan Stern: >> Add void before musb_read to indicate that the register MUSB_DEVCTL >> was intended to be read and discarded. >> --- >>   drivers/usb/musb/musbhsdma.c | 8 +++++--- >>   1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c >> index 0aacfc8be5a1..2a345b4ad015 100644 >> --- a/drivers/usb/musb/musbhsdma.c >> +++ b/drivers/usb/musb/musbhsdma.c > [...] >> @@ -336,7 +334,11 @@ irqreturn_t dma_controller_irq(int irq, void *private_data) >>                           < musb_channel->len) ? >>                       "=> reconfig 0" : "=> complete"); >>   -                devctl = musb_readb(mbase, MUSB_DEVCTL); >> +                /* >> +                 * Some hardware may need to read the >> +                 * MUSB_DEVCTL register once to take effect. >> +                 */ >> +                (void)musb_readb(mbase, MUSB_DEVCTL); > >    Hm, forcibly reading DevCtl in the DMA driver... sounds quite nonsensically. Lemme take a look... Indeed, prior to commit c418fd6c01fbc5516a2cd1eaf1df1ec86869028a ("usb: gadget: musb: fix short isoc packets with inventra dma") the DevCtl read was done in order to check the DevCtl.HostMode bit -- this test was removed but the DevCtl read was left intact... so my vote goes for deleting both the read and the variable... > [...] MBR, Sergei