[PATCH edk2-platforms v2] Silicon/Socionext/SynQuacerI2cDxe: fix TPL handling bug

[PATCH edk2-platforms v2] Silicon/Socionext/SynQuacerI2cDxe: fix TPL handling bug

[Ard Biesheuvel]

Currently, SynQuacerI2cStartRequest() increases the TPL to TPL_HIGH_LEVEL
while accessing the I2C controller hardware, but fails to restore the TPL
to the original level if the call to SynQuacerI2cMasterStart() fails, and
returns right away. Given the TPL_HIGH_LEVEL implies that interrupts are
disabled, this results in a complete system hang. So instead, break out
of the loop, so that the TPL restore will occur before leaving the
function.

Note that this will result in the bus control bits to be de-asserted in
case of a failure to send the START condition, which is an appropriate
cleanup action to take after SynQuacerI2cMasterStart() fails.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
v2: clarify comment and commit log to explain that releasing the bus controls
    is an appropriate action for this failure mode

 Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
index 46c512a20151..5e70f9d921c3 100644
--- a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
+++ b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
@@ -324,7 +324,7 @@ SynQuacerI2cStartRequest (
 
     Status = SynQuacerI2cMasterStart (I2c, SlaveAddress, Op);
     if (EFI_ERROR (Status)) {
-      return Status;
+      break;
     }
 
     Status = WaitForInterrupt (I2c);
@@ -397,7 +397,7 @@ SynQuacerI2cStartRequest (
     } while (BufIdx < Op->LengthInBytes);
   }
 
-  // Stop the transfer
+  // Force bus state to idle, terminating any ongoing transfer
   MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR, 0);
 
   if (!AtRuntime) {
-- 
2.11.0

Re: [PATCH edk2-platforms v2] Silicon/Socionext/SynQuacerI2cDxe: fix TPL handling bug

[Leif Lindholm]

On Wed, Feb 21, 2018 at 11:04:21AM +0000, Ard Biesheuvel wrote:
> Currently, SynQuacerI2cStartRequest() increases the TPL to TPL_HIGH_LEVEL
> while accessing the I2C controller hardware, but fails to restore the TPL
> to the original level if the call to SynQuacerI2cMasterStart() fails, and
> returns right away. Given the TPL_HIGH_LEVEL implies that interrupts are
> disabled, this results in a complete system hang. So instead, break out
> of the loop, so that the TPL restore will occur before leaving the
> function.
> 
> Note that this will result in the bus control bits to be de-asserted in
> case of a failure to send the START condition, which is an appropriate
> cleanup action to take after SynQuacerI2cMasterStart() fails.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> ---
> v2: clarify comment and commit log to explain that releasing the bus controls
>     is an appropriate action for this failure mode
> 
>  Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
> index 46c512a20151..5e70f9d921c3 100644
> --- a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
> +++ b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
> @@ -324,7 +324,7 @@ SynQuacerI2cStartRequest (
>  
>      Status = SynQuacerI2cMasterStart (I2c, SlaveAddress, Op);
>      if (EFI_ERROR (Status)) {
> -      return Status;
> +      break;
>      }
>  
>      Status = WaitForInterrupt (I2c);
> @@ -397,7 +397,7 @@ SynQuacerI2cStartRequest (
>      } while (BufIdx < Op->LengthInBytes);
>    }
>  
> -  // Stop the transfer
> +  // Force bus state to idle, terminating any ongoing transfer
>    MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR, 0);
>  
>    if (!AtRuntime) {
> -- 
> 2.11.0
> 

Re: [PATCH edk2-platforms v2] Silicon/Socionext/SynQuacerI2cDxe: fix TPL handling bug

[Ard Biesheuvel]

On 21 February 2018 at 11:11, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> On Wed, Feb 21, 2018 at 11:04:21AM +0000, Ard Biesheuvel wrote:
>> Currently, SynQuacerI2cStartRequest() increases the TPL to TPL_HIGH_LEVEL
>> while accessing the I2C controller hardware, but fails to restore the TPL
>> to the original level if the call to SynQuacerI2cMasterStart() fails, and
>> returns right away. Given the TPL_HIGH_LEVEL implies that interrupts are
>> disabled, this results in a complete system hang. So instead, break out
>> of the loop, so that the TPL restore will occur before leaving the
>> function.
>>
>> Note that this will result in the bus control bits to be de-asserted in
>> case of a failure to send the START condition, which is an appropriate
>> cleanup action to take after SynQuacerI2cMasterStart() fails.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>
> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
>

Thanks

Pushed as 33d1b85bae27


>> ---
>> v2: clarify comment and commit log to explain that releasing the bus controls
>>     is an appropriate action for this failure mode
>>
>>  Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
>> index 46c512a20151..5e70f9d921c3 100644
>> --- a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
>> +++ b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
>> @@ -324,7 +324,7 @@ SynQuacerI2cStartRequest (
>>
>>      Status = SynQuacerI2cMasterStart (I2c, SlaveAddress, Op);
>>      if (EFI_ERROR (Status)) {
>> -      return Status;
>> +      break;
>>      }
>>
>>      Status = WaitForInterrupt (I2c);
>> @@ -397,7 +397,7 @@ SynQuacerI2cStartRequest (
>>      } while (BufIdx < Op->LengthInBytes);
>>    }
>>
>> -  // Stop the transfer
>> +  // Force bus state to idle, terminating any ongoing transfer
>>    MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR, 0);
>>
>>    if (!AtRuntime) {
>> --
>> 2.11.0
>>