[PATCH v3 1/6] [edk2-platforms] Silicon/SynQuacerI2cDxe: Wait for bus ready

["Masami Hiramatsu" <masami.hiramatsu@linaro.org>]

If an EFI application frequently repeats SetTime and GetTime,
the I2C bus can be busy and failed to start. To fix this issue,
add waiting loop for the bus busy status. (Usually, it is
enough to read 3 times for checking, but for safety this
sets 10 for timeout.)

This also clean up the code path a bit so that it is easy to
understand what should do on each combinations of BSR.BB and
BCR.MSS.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
Reported-by: Kazuhiko Sakamoto <sakamoto.kazuhiko@socionext.com>
---
 Changes in v3:
  - Fix LF to CRLF.
  - Change title to wait for bus ready.
 Changes in v2:
  - Rename WAIT_FOR_BUS_BUSY_TIMEOUT to WAIT_FOR_BUS_READY_TIMEOUT
  - Fix indentation.
---
 .../Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c      |   38 ++++++++++++++------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
index 8aa9799018..c8646db800 100644
--- a/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
+++ b/Silicon/Socionext/SynQuacer/Drivers/SynQuacerI2cDxe/SynQuacerI2cDxe.c
@@ -16,6 +16,8 @@
 //
 #define WAIT_FOR_INTERRUPT_TIMEOUT    50000
 
+#define WAIT_FOR_BUS_READY_TIMEOUT       10
+
 /**
   Set the frequency for the I2C clock line.
 
@@ -152,6 +154,7 @@ SynQuacerI2cMasterStart (
   IN  EFI_I2C_OPERATION           *Op
   )
 {
+  UINTN                       Timeout = WAIT_FOR_BUS_READY_TIMEOUT;
   UINT8                       Bsr;
   UINT8                       Bcr;
 
@@ -167,24 +170,35 @@ SynQuacerI2cMasterStart (
   Bsr = MmioRead8 (I2c->MmioBase + F_I2C_REG_BSR);
   Bcr = MmioRead8 (I2c->MmioBase + F_I2C_REG_BCR);
 
-  if ((Bsr & F_I2C_BSR_BB) && !(Bcr & F_I2C_BCR_MSS)) {
-    DEBUG ((DEBUG_INFO, "%a: bus is busy\n", __FUNCTION__));
-    return EFI_ALREADY_STARTED;
-  }
+  if (!(Bcr & F_I2C_BCR_MSS)) {
 
-  if (Bsr & F_I2C_BSR_BB) { // Bus is busy
-    DEBUG ((DEBUG_INFO, "%a: Continuous Start\n", __FUNCTION__));
-    MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR, Bcr | F_I2C_BCR_SCC);
-  } else {
-    if (Bcr & F_I2C_BCR_MSS) {
-      DEBUG ((DEBUG_WARN,
-        "%a: is not in master mode\n", __FUNCTION__));
-      return EFI_DEVICE_ERROR;
+    if (Bsr & F_I2C_BSR_BB) { // Bus is busy
+        do {
+          Bsr = MmioRead8 (I2c->MmioBase + F_I2C_REG_BSR);
+        } while (Timeout-- && (Bsr & F_I2C_BSR_BB));
+
+        if (Bsr & F_I2C_BSR_BB) {
+          DEBUG ((DEBUG_INFO, "%a: bus is busy\n", __FUNCTION__));
+          return EFI_ALREADY_STARTED;
+        }
     }
+
     DEBUG ((DEBUG_INFO, "%a: Start Condition\n", __FUNCTION__));
     MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR,
                 Bcr | F_I2C_BCR_MSS | F_I2C_BCR_INTE | F_I2C_BCR_BEIE);
+
+  } else { // F_I2C_BCR_MSS is set
+
+    if (!(Bsr & F_I2C_BSR_BB)) {
+      DEBUG ((DEBUG_WARN,
+        "%a: is not in master mode\n", __FUNCTION__));
+      return EFI_DEVICE_ERROR;
+    }
+
+    DEBUG ((DEBUG_INFO, "%a: Continuous Start\n", __FUNCTION__));
+    MmioWrite8 (I2c->MmioBase + F_I2C_REG_BCR, Bcr | F_I2C_BCR_SCC);
   }
+
   return EFI_SUCCESS;
 }