[edk2] [PATCH] EmbeddedPkg/DwEmmcDxe: limit max clock for platform

[Jun Nie]

Some boards may have max clock limitation. Add a Pcd to notify
driver.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jun Nie <jun....@linaro.org>
---
 EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.c   | 4 ++++
 EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.inf | 1 +
 EmbeddedPkg/EmbeddedPkg.dec                 | 1 +
 3 files changed, 6 insertions(+)

diff --git a/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.c 
b/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.c
index fe23d11..308f3a7 100644
--- a/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.c
+++ b/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.c
@@ -560,6 +560,10 @@ DwEmmcSetIos (
   EFI_STATUS Status = EFI_SUCCESS;
   UINT32    Data;
 
+  if (BusClockFreq > PcdGet32 (PcdDwEmmcDxeMaxClockFrequencyInHz)) {
+    return EFI_UNSUPPORTED;
+  }
+
   if (TimingMode != EMMCBACKWARD) {
     Data = MmioRead32 (DWEMMC_UHSREG);
     switch (TimingMode) {
diff --git a/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.inf 
b/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.inf
index e3c8313..3582997 100644
--- a/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.inf
+++ b/EmbeddedPkg/Drivers/DwEmmcDxe/DwEmmcDxe.inf
@@ -48,6 +48,7 @@
 [Pcd]
   gEmbeddedTokenSpaceGuid.PcdDwEmmcDxeBaseAddress
   gEmbeddedTokenSpaceGuid.PcdDwEmmcDxeClockFrequencyInHz
+  gDwEmmcDxeTokenSpaceGuid.PcdDwEmmcDxeMaxClockFrequencyInHz
 
 [Depex]
   TRUE
diff --git a/EmbeddedPkg/EmbeddedPkg.dec b/EmbeddedPkg/EmbeddedPkg.dec
index 0d4a062..aec8259 100644
--- a/EmbeddedPkg/EmbeddedPkg.dec
+++ b/EmbeddedPkg/EmbeddedPkg.dec
@@ -167,6 +167,7 @@
   # DwEmmc Driver PCDs
   gEmbeddedTokenSpaceGuid.PcdDwEmmcDxeBaseAddress|0x0|UINT32|0x00000035
   gEmbeddedTokenSpaceGuid.PcdDwEmmcDxeClockFrequencyInHz|0x0|UINT32|0x00000036
+  
gDwEmmcDxeTokenSpaceGuid.PcdDwEmmcDxeMaxClockFrequencyInHz|0x0|UINT32|400000000
 
   #
   # Android FastBoot
-- 
1.9.1

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