[11/30] usb: dwc2: gadget: Avoid pointless read of EP control register

Message ID 20200702144625.2533530-12-lee.jones@linaro.org
State Superseded
Headers show
Series
  • Fix a bunch of W=1 issues in USB
Related show

Commit Message

Lee Jones July 2, 2020, 2:46 p.m.
Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved
these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned
value hasn't been read back since.  Let's remove the unnecessary H/W read.

Fixes the following W=1 warning:

 drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:
 drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]
 2981 | u32 ctrl;
 | ^~~~

Cc: Minas Harutyunyan <hminas@synopsys.com>
Cc: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

---
 drivers/usb/dwc2/gadget.c | 2 --
 1 file changed, 2 deletions(-)

-- 
2.25.1

Comments

Greg KH July 3, 2020, 7:29 a.m. | #1
On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:
> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

> value hasn't been read back since.  Let's remove the unnecessary H/W read.

> 

> Fixes the following W=1 warning:

> 

>  drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

>  drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

>  2981 | u32 ctrl;

>  | ^~~~

> 

> Cc: Minas Harutyunyan <hminas@synopsys.com>

> Cc: Ben Dooks <ben@simtec.co.uk>

> Signed-off-by: Lee Jones <lee.jones@linaro.org>

> ---

>  drivers/usb/dwc2/gadget.c | 2 --

>  1 file changed, 2 deletions(-)

> 

> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

> index 116e6175c7a48..fa07e3fcb8841 100644

> --- a/drivers/usb/dwc2/gadget.c

> +++ b/drivers/usb/dwc2/gadget.c

> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

>  	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

>  	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

>  	u32 ints;

> -	u32 ctrl;

>  

>  	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

> -	ctrl = dwc2_readl(hsotg, epctl_reg);


As you know, lots of hardware requires reads to happen to do things, so
are you sure it is safe to remove this read call?

thanks,

greg k-h
Minas Harutyunyan July 3, 2020, 7:38 a.m. | #2
Hi,

On 7/3/2020 11:29 AM, Greg KH wrote:
> On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:

>> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

>> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

>> value hasn't been read back since.  Let's remove the unnecessary H/W read.

>>

>> Fixes the following W=1 warning:

>>

>>   drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

>>   drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

>>   2981 | u32 ctrl;

>>   | ^~~~

>>

>> Cc: Minas Harutyunyan <hminas@synopsys.com>

>> Cc: Ben Dooks <ben@simtec.co.uk>

>> Signed-off-by: Lee Jones <lee.jones@linaro.org>

>> ---

>>   drivers/usb/dwc2/gadget.c | 2 --

>>   1 file changed, 2 deletions(-)

>>

>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

>> index 116e6175c7a48..fa07e3fcb8841 100644

>> --- a/drivers/usb/dwc2/gadget.c

>> +++ b/drivers/usb/dwc2/gadget.c

>> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

>>   	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

>>   	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

>>   	u32 ints;

>> -	u32 ctrl;

>>   

>>   	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

>> -	ctrl = dwc2_readl(hsotg, epctl_reg);

> 

> As you know, lots of hardware requires reads to happen to do things, so

> are you sure it is safe to remove this read call?

> 


Greg, yes, it's Ok to remove this unnecessary read which remained from 
previous implementations.

Lee, please add "Fixes:" tag and resubmit v2.

Thanks,
Minas


> thanks,

> 

> greg k-h

>
Greg KH July 3, 2020, 7:43 a.m. | #3
On Fri, Jul 03, 2020 at 07:38:16AM +0000, Minas Harutyunyan wrote:
> Hi,

> 

> On 7/3/2020 11:29 AM, Greg KH wrote:

> > On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:

> >> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

> >> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

> >> value hasn't been read back since.  Let's remove the unnecessary H/W read.

> >>

> >> Fixes the following W=1 warning:

> >>

> >>   drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

> >>   drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

> >>   2981 | u32 ctrl;

> >>   | ^~~~

> >>

> >> Cc: Minas Harutyunyan <hminas@synopsys.com>

> >> Cc: Ben Dooks <ben@simtec.co.uk>

> >> Signed-off-by: Lee Jones <lee.jones@linaro.org>

> >> ---

> >>   drivers/usb/dwc2/gadget.c | 2 --

> >>   1 file changed, 2 deletions(-)

> >>

> >> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

> >> index 116e6175c7a48..fa07e3fcb8841 100644

> >> --- a/drivers/usb/dwc2/gadget.c

> >> +++ b/drivers/usb/dwc2/gadget.c

> >> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

> >>   	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

> >>   	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

> >>   	u32 ints;

> >> -	u32 ctrl;

> >>   

> >>   	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

> >> -	ctrl = dwc2_readl(hsotg, epctl_reg);

> > 

> > As you know, lots of hardware requires reads to happen to do things, so

> > are you sure it is safe to remove this read call?

> > 

> 

> Greg, yes, it's Ok to remove this unnecessary read which remained from 

> previous implementations.


Great, thanks for confirming!

greg k-h
Minas Harutyunyan July 3, 2020, 8:35 a.m. | #4
Hi,

On 7/3/2020 11:43 AM, Greg KH wrote:
> On Fri, Jul 03, 2020 at 07:38:16AM +0000, Minas Harutyunyan wrote:

>> Hi,

>>

>> On 7/3/2020 11:29 AM, Greg KH wrote:

>>> On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:

>>>> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

>>>> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

>>>> value hasn't been read back since.  Let's remove the unnecessary H/W read.

>>>>

>>>> Fixes the following W=1 warning:

>>>>

>>>>    drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

>>>>    drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

>>>>    2981 | u32 ctrl;

>>>>    | ^~~~

>>>>

>>>> Cc: Minas Harutyunyan <hminas@synopsys.com>

>>>> Cc: Ben Dooks <ben@simtec.co.uk>

>>>> Signed-off-by: Lee Jones <lee.jones@linaro.org>

>>>> ---

>>>>    drivers/usb/dwc2/gadget.c | 2 --

>>>>    1 file changed, 2 deletions(-)

>>>>

>>>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

>>>> index 116e6175c7a48..fa07e3fcb8841 100644

>>>> --- a/drivers/usb/dwc2/gadget.c

>>>> +++ b/drivers/usb/dwc2/gadget.c

>>>> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

>>>>    	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

>>>>    	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

>>>>    	u32 ints;

>>>> -	u32 ctrl;

>>>>    

>>>>    	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

>>>> -	ctrl = dwc2_readl(hsotg, epctl_reg);

>>>

>>> As you know, lots of hardware requires reads to happen to do things, so

>>> are you sure it is safe to remove this read call?

>>>

>>

>> Greg, yes, it's Ok to remove this unnecessary read which remained from

>> previous implementations.

> 

> Great, thanks for confirming!

> 


Acked-by: Minas Harutyunyan <hminas@synopsys.com>


> greg k-h

>
Lee Jones July 3, 2020, 5:16 p.m. | #5
On Fri, 03 Jul 2020, Minas Harutyunyan wrote:

> Hi,

> 

> On 7/3/2020 11:29 AM, Greg KH wrote:

> > On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:

> >> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

> >> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

> >> value hasn't been read back since.  Let's remove the unnecessary H/W read.

> >>

> >> Fixes the following W=1 warning:

> >>

> >>   drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

> >>   drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

> >>   2981 | u32 ctrl;

> >>   | ^~~~

> >>

> >> Cc: Minas Harutyunyan <hminas@synopsys.com>

> >> Cc: Ben Dooks <ben@simtec.co.uk>

> >> Signed-off-by: Lee Jones <lee.jones@linaro.org>

> >> ---

> >>   drivers/usb/dwc2/gadget.c | 2 --

> >>   1 file changed, 2 deletions(-)

> >>

> >> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

> >> index 116e6175c7a48..fa07e3fcb8841 100644

> >> --- a/drivers/usb/dwc2/gadget.c

> >> +++ b/drivers/usb/dwc2/gadget.c

> >> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

> >>   	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

> >>   	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

> >>   	u32 ints;

> >> -	u32 ctrl;

> >>   

> >>   	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

> >> -	ctrl = dwc2_readl(hsotg, epctl_reg);

> > 

> > As you know, lots of hardware requires reads to happen to do things, so

> > are you sure it is safe to remove this read call?

> > 

> 

> Greg, yes, it's Ok to remove this unnecessary read which remained from 

> previous implementations.

> 

> Lee, please add "Fixes:" tag and resubmit v2.


Is this suitable for Stable Greg?

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog
Greg KH July 4, 2020, 6:04 a.m. | #6
On Fri, Jul 03, 2020 at 06:16:26PM +0100, Lee Jones wrote:
> On Fri, 03 Jul 2020, Minas Harutyunyan wrote:

> 

> > Hi,

> > 

> > On 7/3/2020 11:29 AM, Greg KH wrote:

> > > On Thu, Jul 02, 2020 at 03:46:06PM +0100, Lee Jones wrote:

> > >> Commit ec1f9d9f01384 ("usb: dwc2: gadget: parity fix in isochronous mode") moved

> > >> these checks to dwc2_hsotg_change_ep_iso_parity() back in 2015.  The assigned

> > >> value hasn't been read back since.  Let's remove the unnecessary H/W read.

> > >>

> > >> Fixes the following W=1 warning:

> > >>

> > >>   drivers/usb/dwc2/gadget.c: In function ‘dwc2_hsotg_epint’:

> > >>   drivers/usb/dwc2/gadget.c:2981:6: warning: variable ‘ctrl’ set but not used [-Wunused-but-set-variable]

> > >>   2981 | u32 ctrl;

> > >>   | ^~~~

> > >>

> > >> Cc: Minas Harutyunyan <hminas@synopsys.com>

> > >> Cc: Ben Dooks <ben@simtec.co.uk>

> > >> Signed-off-by: Lee Jones <lee.jones@linaro.org>

> > >> ---

> > >>   drivers/usb/dwc2/gadget.c | 2 --

> > >>   1 file changed, 2 deletions(-)

> > >>

> > >> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c

> > >> index 116e6175c7a48..fa07e3fcb8841 100644

> > >> --- a/drivers/usb/dwc2/gadget.c

> > >> +++ b/drivers/usb/dwc2/gadget.c

> > >> @@ -2975,10 +2975,8 @@ static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,

> > >>   	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);

> > >>   	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);

> > >>   	u32 ints;

> > >> -	u32 ctrl;

> > >>   

> > >>   	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);

> > >> -	ctrl = dwc2_readl(hsotg, epctl_reg);

> > > 

> > > As you know, lots of hardware requires reads to happen to do things, so

> > > are you sure it is safe to remove this read call?

> > > 

> > 

> > Greg, yes, it's Ok to remove this unnecessary read which remained from 

> > previous implementations.

> > 

> > Lee, please add "Fixes:" tag and resubmit v2.

> 

> Is this suitable for Stable Greg?


Does it fix something that people have ever noticed or care about?
Given the age of the bug, I doubt it :)

thanks,

greg k-h

Patch

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 116e6175c7a48..fa07e3fcb8841 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -2975,10 +2975,8 @@  static void dwc2_hsotg_epint(struct dwc2_hsotg *hsotg, unsigned int idx,
 	u32 epctl_reg = dir_in ? DIEPCTL(idx) : DOEPCTL(idx);
 	u32 epsiz_reg = dir_in ? DIEPTSIZ(idx) : DOEPTSIZ(idx);
 	u32 ints;
-	u32 ctrl;
 
 	ints = dwc2_gadget_read_ep_interrupts(hsotg, idx, dir_in);
-	ctrl = dwc2_readl(hsotg, epctl_reg);
 
 	/* Clear endpoint interrupts */
 	dwc2_writel(hsotg, ints, epint_reg);