Hi, On Thu, 24 Dec 2020 at 03:47, Yusuf Kaya <[email protected]> wrote: > > Hi, > > I'm confused about usage of DCC(Data DWord Count) Field of PRD Entries in > fsl_sata.c > > In T1042 Reference manual, DCC field is explained as the following way; > > Data DWord count. A 0-based value that Indicates the length, in DWords, of > the data block. A > maximum length of 32 Mbytes may exist for any entry. Bits 1-0 of this field > must always be 0 to > indicate that size is in 4-byte words. A value of 24'b0 indicates a full 32 > Mbytes transfer. > > but in the fsl driver code of u-boot, this field is acted like DBC(Data Byte > Count). The following is part of the driver code that handles PRD Entries > > > if (len < PRD_ENTRY_MAX_XFER_SZ) { > ext_c_ddc = PRD_ENTRY_DATA_SNOOP | len; > debug("ext_c_ddc1 = %08x, len = %08x\n\r", ext_c_ddc, len); > prde->ext_c_ddc = cpu_to_le32(ext_c_ddc); > prde_count++; > prde++; > break; > } else { > ext_c_ddc = PRD_ENTRY_DATA_SNOOP; /* 4M bytes */ > debug("ext_c_ddc2 = %08x, len = %08x\n\r", ext_c_ddc, len); > prde->ext_c_ddc = cpu_to_le32(ext_c_ddc); > buffer += PRD_ENTRY_MAX_XFER_SZ; > len -= PRD_ENTRY_MAX_XFER_SZ; > prde_count++; > prde++; > } > > > In the above code, PRD_ENTRY_MAX_XFER_SZ is defined as 4 MB and DDC > field of PDR entries are using like DBC. I didnt understand that part of > the code and Reference Manual also specifies maximum transfer size of > data is 32 Mbytes not 4Mbytes. > > > the fsl sata driver code of u-boot is working but according to t1042 > reference manual it should work wrongly. > > > I guess I misunderstand something about PRD Entries. Could you explain it for > me ?
I assume this is fsl_sata.c so: +Peng Fan Regards, Simon
