Qiang Li - Mpu Se

The DMA buffer size in WinCE IMX ESDHC driver -blog archive

Discussion created by Qiang Li - Mpu Se Employee on Feb 14, 2012

    The ESDHC driver has no such limitation for DMA buffer size, for ADMA mode, the max buffer size is 64KB (This is not the once DMA transfer max size, ADMA can use chain to transfer more buffers in once DMA), we can reference to "Figure 20-31. Format of the Descriptor Table" in iMX35 reference manual, there are 16 bits "Data Length" in ADMA description.

    Reference to the WinCE SDBUS driver architecture, the DMA data buffers are alloced in SD device drivers (such as SD memory driver), not in ESDHC driver. The ESDHC driver will only fill the SD device driver's data buffer address and length into the ADMA descriptions, and only the DMA descriptions are alloced in ESDHC driver.