drivers/scsi/sata_sx4.c: In function `pdc20621_put_to_dimm':
drivers/scsi/sata_sx4.c:928: warning: comparison is always true due to limited range of data type

The code is doing, effectively:

	if ((long)(expr returning u32)) >= 0

but on 64-bit architectures, that will always be true.

So cast the u32 result to s32 before promoting to long so that bit 31
correctly propagates into bits 32-63.