Hi Pierre, Thanks for reviewing the patchset. Please find my comment inline below.

On Thu, 2 May 2024 at 18:47, PierreGondois via groups.io <pierre.gondois=arm.com@groups.io> wrote:
>
> Hello Sahil,
>
> On 4/23/24 07:56, Sahil Kaushal via groups.io wrote:
> > From: sahil <sahil@arm.com>
> >
> > In N1Sdp platform, the SoC is connected to IOFPGA which has a
> > Cadence Quad SPI (QSPI) controller. This QSPI controller manages
> > the flash chip device via QSPI bus.
> >
> > This patch adds CadenceQspiNorFlashDeviceLib which is used to
> > manage and access the above configuration.
> >
> > Signed-off-by: sahil <sahil@arm.com>
> > ---
> > Platform/ARM/Library/CadenceQspiNorFlashDeviceLib/CadenceQspiNorFlashDeviceLib.inf | 32 +
> > Platform/ARM/Library/CadenceQspiNorFlashDeviceLib/CadenceQspiNorFlashDeviceLib.h | 44 +
> > Platform/ARM/Library/CadenceQspiNorFlashDeviceLib/CadenceQspiNorFlashDeviceLib.c | 1011 ++++++++++++++++++++
> > 3 files changed, 1087 insertions(+)
> >
>
> [snip]
>
> > +
> > +/**
> > + Converts milliseconds into number of ticks of the performance counter.
> > +
> > + @param[in] Milliseconds Milliseconds to convert into ticks.
> > +
> > + @retval Milliseconds expressed as number of ticks.
> > +
> > +**/
> > +STATIC
> > +UINT64
> > +MilliSecondsToTicks (
> > + IN UINTN Milliseconds
> > + )
> > +{
> > + CONST UINT64 NanoSecondsPerTick = GetTimeInNanoSecond (1);
> > +
> > + return (Milliseconds * 1000000) / NanoSecondsPerTick;
>
> Should use DivU64x64Remainder() here:
> {
> UINT64 NanoSecondsPerTick;
> UINT64 NanoSeconds;
>
> NanoSecondsPerTick = GetTimeInNanoSecond (1);
> NanoSeconds = MultU64x32 (Milliseconds, 1000000);
>
> return DivU64x64Remainder (NanoSeconds, NanoSecondsPerTick, NULL);
> }
>
> > +}
> > +
> > +/**
> > + Poll Status register for NOR flash erase/write completion.
> > +
> > + @param[in] Instance NOR flash Instance.
> > +
> > + @retval EFI_SUCCESS Request is executed successfully.
> > + @retval EFI_TIMEOUT Operation timed out.
> > + @retval EFI_DEVICE_ERROR Controller operartion failed.
>
> operartion -> typo
> (same at another place I think)
>
> [snip]
>
> > +
> > +/**
> > + Read from nor flash.
> > +
> > + @param[in] Instance NOR flash Instance of variable store region.
> > + @param[in] Lba The starting logical block index to read from.
> > + @param[in] Offset Offset into the block at which to begin reading.
> > + @param[in] BufferSizeInBytes The number of bytes to read.
> > + @param[out] Buffer The pointer to a caller-allocated buffer that
> > + should copied with read data.
> > +
> > + @retval EFI_SUCCESS The read is completed.
> > + @retval EFI_INVALID_PARAMETER Invalid parameters passed.
> > +**/
> > +EFI_STATUS
> > +NorFlashRead (
> > + IN NOR_FLASH_INSTANCE *Instance,
> > + IN EFI_LBA Lba,
> > + IN UINTN Offset,
> > + IN UINTN BufferSizeInBytes,
> > + OUT VOID *Buffer
> > + )
> > +{
> > + UINTN StartAddress;
> > +
> > + // The buffer must be valid
> > + if (Buffer == NULL) {
> > + return EFI_INVALID_PARAMETER;
> > + }
> > +
> > + // Return if we do not have any byte to read
> > + if (BufferSizeInBytes == 0) {
> > + return EFI_SUCCESS;
> > + }
> > +
> > + if (((Lba * Instance->Media.BlockSize) + Offset + BufferSizeInBytes) >
> > + Instance->Size)
> > + {
> > + DEBUG ((
> > + DEBUG_ERROR,
> > + "NorFlashRead: ERROR - Read will exceed device size.\n"
> > + ));
> > + return EFI_INVALID_PARAMETER;
> > + }
> > +
> > + // Get the address to start reading from
> > + StartAddress = GET_NOR_BLOCK_ADDRESS (
> > + Instance->RegionBaseAddress,
> > + Lba,
> > + Instance->Media.BlockSize
> > + );
> > +
> > + // Readout the data
> > + CopyMem (Buffer, (UINTN *)(StartAddress + Offset), BufferSizeInBytes);
>
> The original code at:
> Platform/ARM/Library/P30NorFlashDeviceLib/P30NorFlashDeviceLib.c
>
> implements and uses AlignedCopyMem()/NorFlashWriteBuffer() which seems
> to be more efficient.
> Just to be sure I understand correctly, is the maximal read/write size
> of 4 bytes ? Meaning that these functions are not needed ?
>
> ---
>
> NorFlashWriteBuffer() is not implemented here IIUC won't be implemtned as not
> needed. Maybe in an additional patch, the function could be removed from the
> library interface at:
> Platform/ARM/Include/Library/NorFlashDeviceLib.h
> and made static in:
> Platform/ARM/Library/P30NorFlashDeviceLib/P30NorFlashDeviceLib.c
>
CopyMem() and AlignedCopyMem() have nearly identical implementations, therefore I think we can
continue using CopyMem() here.

For NorFlashWriteBuffer(), in the P30 spec, it looks like buffered programming is one of the features
of the IP whereas there is no such feature in cadence IP. So, I think there is no need for
NorFlashWriteBuffer() for Cadence controller Library.

I will push another patch in the next patchset to remove NorFlashWriteBuffer() from the

NorFlashDeviceLib.h header file.