Re: [Linaro-uefi] [edk2] [PATCH v2 2/2] ArmPlatformPkg: PL061: fix accessing gpio value

On 11 August 2015 at 11:42, Haojian Zhuang haojian.zhuang@linaro.org wrote:

The way of accessing PL061 GPIODATA register is wrong.

The spec said in below.

In order to write to GPIODATA, the corresponding bits in the mask, resulting from the address bus, PADDR[9:2], must be HIGH. Otherwise the bit values remain unchanged by the write. Similarly, the values read from this register are determined for each bit, by the mask bit derived from the address used to access the data register, PADDR[9:2]. Bits that are 1 in the address mask cause the corresponding bits in GPIODATA to be read, and bits that are 0 in the address mask cause the corresponding bits in GPIODATA to be read as 0, regardless of their value.

Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Haojian Zhuang haojian.zhuang@linaro.org

---

ArmPlatformPkg/Drivers/PL061GpioDxe/PL061Gpio.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/ArmPlatformPkg/Drivers/PL061GpioDxe/PL061Gpio.c b/ArmPlatformPkg/Drivers/PL061GpioDxe/PL061Gpio.c index ff05662..35418c9 100644 --- a/ArmPlatformPkg/Drivers/PL061GpioDxe/PL061Gpio.c +++ b/ArmPlatformPkg/Drivers/PL061GpioDxe/PL061Gpio.c @@ -125,7 +125,7 @@ Get ( } }

• if (MmioRead8 (PL061_GPIO_DATA_REG) & GPIO_PIN_MASK_HIGH_8BIT(Gpio)) {

• if (MmioRead8 (PL061_GPIO_DATA_REG + (GPIO_PIN_MASK_HIGH_8BIT(Gpio) << 2))) { *Value = 1; } else { *Value = 0;

@@ -186,14 +186,14 @@ Set (

 case GPIO_MODE_OUTPUT_0:
   // Set the corresponding data bit to LOW for 0

•  MmioAnd8 (PL061_GPIO_DATA_REG, GPIO_PIN_MASK_LOW_8BIT(Gpio));
  

•  MmioAnd8 (PL061_GPIO_DATA_REG + (GPIO_PIN_MASK_HIGH_8BIT(Gpio) << 2), GPIO_PIN_MASK_LOW_8BIT(Gpio));
  

There is no reason for a read/and/write sequence here: the mask will ensure that you can only affect the selected GPIO, so instead, you can simply use MmioWrite8(<addr>, 0x0)

   // Set the corresponding direction bit to HIGH for output
   MmioOr8 (PL061_GPIO_DIR_REG, GPIO_PIN_MASK_HIGH_8BIT(Gpio));
   break;

 case GPIO_MODE_OUTPUT_1:
   // Set the corresponding data bit to HIGH for 1

•  MmioOr8 (PL061_GPIO_DATA_REG, GPIO_PIN_MASK_HIGH_8BIT(Gpio));
  

•  MmioOr8 (PL061_GPIO_DATA_REG + (GPIO_PIN_MASK_HIGH_8BIT(Gpio) << 2), GPIO_PIN_MASK_HIGH_8BIT(Gpio));
  

Likewise, but use MmioWrite8(addr, 0xff) in this case

   // Set the corresponding direction bit to HIGH for output
   MmioOr8 (PL061_GPIO_DIR_REG, GPIO_PIN_MASK_HIGH_8BIT(Gpio));
   break;

There is another place in the file that uses the same broken logic, inside GetMode(). Could you please fix that as well?