7 years, 5 months ago.

Renesas RZ/A1H L1 cache flushing and DMA - why not found in USBDevice

Why does the USBDevice driver (and also the R_BSP library) for this processor in mbed omit all reference to L1 cache flushing? The Renesas DMA example code (in application note R01AN1703EJ0101) makes use of L1_D_CacheWritebackFlushAll() and L1_D_CacheFlushAll() at the beginning and end of DMA transfers between a internal memory and an integrated peripheral.

I have found these cache routines to be essential to the successful use of DMA.

Question relating to:

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R_BSP has been designed on the assumption that the use of non-cache memory to transfer buffer. Therefore, there is no clear process of cache.

Do not use the DMA in USB Device. Processing of the case to use a DMA in the code contains, but it is not actually used. When using DMA in USBDevice, it's necessary to use non-cache memory.

posted by XtrmDesignsLLC GRPeach 11 Jul 2016

1 Answer

7 years, 4 months ago.

Hi Adam, We are checking on this - as GR-PEACH board on mbed.org is supported it does not have any external RAM or SDRAM. R01AN1703EJ0101 Rev.1.01 is a more general device/SoC use Application note where an external SDRAM can have DMA setup for L1 Cache area and the three members of RZA family RZAH/M/L have different sizes of SoC RAM 10,8,3MB. These instructions will not work on GR-PEACH.

DMA driver is available from R_BSP library.

Import libraryR_BSP


Last commit 31 May 2016 by Renesas



The DMA driver is used in the following cord.

R_BSP/RenesasBSP/drv_src/ssif R_BSP/RenesasBSP/drv_src/scux

posted by XtrmDesignsLLC GRPeach 10 Jul 2016