[PATCH v3] usb: musb: remove unused variable 'devctl'

[PATCH v3] usb: musb: remove unused variable 'devctl'

[min.guo]

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>
---
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
@@ -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
@@ -336,7 +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);
 
 				channel->status = MUSB_DMA_STATUS_FREE;
 
-- 
2.18.0

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

[Sergei Shtylyov]

Hello!

On 24.11.2020 11:49, 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>
> ---
> 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

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

[Sergei Shtylyov]

On 11/24/20 12:13 PM, Sergei Shtylyov 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>
>> ---
>> 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

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

[Greg Kroah-Hartman]

On Tue, Nov 24, 2020 at 12:13:42PM +0300, Sergei Shtylyov wrote:
> Hello!
> 
> On 24.11.2020 11:49, 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>
> > ---
> > 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?

thanks,

greg k-h

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

[Sergei Shtylyov]

On 12/10/20 6:01 PM, Greg Kroah-Hartman 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>
>>> ---
>>> 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