On Mon, Jul 03, 2017 at 12:01:56PM +0800, Jun Nie wrote:
> 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)) {
This snippet means that any platform that was using this driver
successfully, but where BusClockFreq is higher than the default value
of this Pcd will stop working.
> + 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
And this definition sets the default value of this Pcd to 0. Meaning
that all existing drivers would stop working.
Also, 0x00000037 would seem like a more suitable Token than 400000000.
If introducing a new limit value like this, I would strongly recommend
making "0" a magic value meaning "no restrictions".
i.e.
UINT32 MaxFreq;
MaxFreq = PcdGet32 (PcdDwEmmcDxeMaxClockFrequencyInHz);
if ((MaxFreq != 0) && (BusClockFreq > MaxFreq)) {
/
Leif
>
> #
> # Android FastBoot
> --
> 1.9.1
>
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