linux-kernel - Re: [PATCH v3] usb: musb: remove unused variable 'devctl'

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Message-ID: <c2f3f643-8514-5c4a-dd52-7abc8a6dc501@gmail.com>
Date:   Tue, 24 Nov 2020 12:13:42 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     min.guo@...iatek.com, Bin Liu <b-liu@...com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Matthias Brugger <matthias.bgg@...il.com>,
        chunfeng.yun@...iatek.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3] usb: musb: remove unused variable 'devctl'

Hello!

On 24.11.2020 11:49, min.guo@...iatek.com wrote:

> From: Min Guo <min.guo@...iatek.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@...iatek.com>
> ---
> 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...

[...]

MBR, Sergei