[Qemu-devel] [PATCH] hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

[Qemu-devel] [PATCH] hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

[Peter Maydell]

Fix a bug in handling the write-one-to-clear bits in the PMCR
which meant that we would always clear the bit even if the
value written was a zero. Spotted by Coverity (see bug 887883).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/pxa2xx.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/hw/pxa2xx.c b/hw/pxa2xx.c
index bfc28a9..d38b922 100644
--- a/hw/pxa2xx.c
+++ b/hw/pxa2xx.c
@@ -114,7 +114,9 @@ static void pxa2xx_pm_write(void *opaque, target_phys_addr_t addr,
 
     switch (addr) {
     case PMCR:
-        s->pm_regs[addr >> 2] &= 0x15 & ~(value & 0x2a);
+        /* Clear the write-one-to-clear bits... */
+        s->pm_regs[addr >> 2] &= ~(value & 0x2a);
+        /* ...and set the plain r/w bits */
         s->pm_regs[addr >> 2] |= value & 0x15;
         break;
 
-- 
1.7.1

Re: [Qemu-devel] [PATCH] hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

[Anthony Liguori]

On 11/09/2011 02:46 PM, Peter Maydell wrote:
> Fix a bug in handling the write-one-to-clear bits in the PMCR
> which meant that we would always clear the bit even if the
> value written was a zero. Spotted by Coverity (see bug 887883).
>
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>   hw/pxa2xx.c |    4 +++-
>   1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/hw/pxa2xx.c b/hw/pxa2xx.c
> index bfc28a9..d38b922 100644
> --- a/hw/pxa2xx.c
> +++ b/hw/pxa2xx.c
> @@ -114,7 +114,9 @@ static void pxa2xx_pm_write(void *opaque, target_phys_addr_t addr,
>
>       switch (addr) {
>       case PMCR:
> -        s->pm_regs[addr>>  2]&= 0x15&  ~(value&  0x2a);
> +        /* Clear the write-one-to-clear bits... */
> +        s->pm_regs[addr>>  2]&= ~(value&  0x2a);
> +        /* ...and set the plain r/w bits */
>           s->pm_regs[addr>>  2] |= value&  0x15;
>           break;
>

Re: [Qemu-devel] [PATCH] hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

[andrzej zaborowski]

Hi,

On 11 November 2011 20:45, Anthony Liguori <anthony@codemonkey.ws> wrote:
> On 11/09/2011 02:46 PM, Peter Maydell wrote:
>>
>> Fix a bug in handling the write-one-to-clear bits in the PMCR
>> which meant that we would always clear the bit even if the
>> value written was a zero. Spotted by Coverity (see bug 887883).
>>
>> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
>
> Applied.  Thanks.
>
> Regards,
>
> Anthony Liguori
>
>> ---
>>  hw/pxa2xx.c |    4 +++-
>>  1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/pxa2xx.c b/hw/pxa2xx.c
>> index bfc28a9..d38b922 100644
>> --- a/hw/pxa2xx.c
>> +++ b/hw/pxa2xx.c
>> @@ -114,7 +114,9 @@ static void pxa2xx_pm_write(void *opaque,
>> target_phys_addr_t addr,
>>
>>      switch (addr) {
>>      case PMCR:
>> -        s->pm_regs[addr>>  2]&= 0x15&  ~(value&  0x2a);
>> +        /* Clear the write-one-to-clear bits... */
>> +        s->pm_regs[addr>>  2]&= ~(value&  0x2a);
>> +        /* ...and set the plain r/w bits */
>>          s->pm_regs[addr>>  2] |= value&  0x15;

As I was about to push these patches also, I noticed this isn't
exactly setting the r/w bits.  But it would work if the first line was
(~value) & 0x2a instead, should I fix it this way, am I looking at it
right?

Cheers

Re: [Qemu-devel] [PATCH] hw/pxa2xx.c: Fix handling of R/WC bits in PMCR

[Peter Maydell]

On 11 November 2011 21:05, andrzej zaborowski <balrogg@gmail.com> wrote:
>>> -        s->pm_regs[addr>>  2]&= 0x15&  ~(value&  0x2a);
>>> +        /* Clear the write-one-to-clear bits... */
>>> +        s->pm_regs[addr>>  2]&= ~(value&  0x2a);
>>> +        /* ...and set the plain r/w bits */
>>>          s->pm_regs[addr>>  2] |= value&  0x15;
>
> As I was about to push these patches also, I noticed this isn't
> exactly setting the r/w bits.  But it would work if the first line was
> (~value) & 0x2a instead, should I fix it this way, am I looking at it
> right?

Rats, you're right. Your fix works (although it renders the comment wrong
as it's then not just clearing the W1C bits). Alternatively add an
extra line to give:

        /* Clear the write-one-to-clear bits... */
        s->pm_regs[addr >> 2] &= ~(value & 0x2a);
        /* ...and set the plain r/w bits */
        s->pm_regs[addr >> 2] &= ~0x15;
        s->pm_regs[addr>>  2] |= value & 0x15;

(this is slightly different in effect from your code in that it
leaves register bits [31:5] untouched where yours will always clear
them.) Feel free to do whichever you think is clearest.

-- PMM