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

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Date:   Thu, 10 Dec 2020 20:33:30 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     min.guo@...iatek.com, Bin Liu <b-liu@...com>,
        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'

On 12/10/20 6:01 PM, Greg Kroah-Hartman 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...
> 
> What happened to your look?

   I thought I posted it the same day... Indeed, here it is, archived:

https://marc.info/?l=linux-usb&m=160621841910477

> thanks,
> 
> greg k-h

MBR, Sergei