Added notes about the controller and driver Signed-off-by: Punnaiah Choudary Kalluri <punnaia@xxxxxxxxxx> --- Documentation/mtd/nand/pl353-nand.txt | 92 +++++++++++++++++++++++++++++++++ 1 files changed, 92 insertions(+), 0 deletions(-) create mode 100644 Documentation/mtd/nand/pl353-nand.txt diff --git a/Documentation/mtd/nand/pl353-nand.txt b/Documentation/mtd/nand/pl353-nand.txt new file mode 100644 index 0000000..4deac94 --- /dev/null +++ b/Documentation/mtd/nand/pl353-nand.txt @@ -0,0 +1,92 @@ +This documents provides some notes about the ARM pl353 smc controller used in +Zynq SOC and confined to NAND specific details. + +Overview of the controller +========================== + The SMC (PL353) supports two memory interfaces: + Interface 0 type SRAM. + Interface 1 type NAND. + This configuration supports the following configurable options: + . 32-bit or 64-bit AXI data width + . 8-bit, 16-bit, or 32-bit memory data width for interface 0 + . 8-bit, or 16-bit memory data width for interface 1 + . 1-4 chip selects on each interface + . SLC ECC block for interface 1 + +For more information, refer the below link for TRM +http://infocenter.arm.com/help/topic/com.arm.doc.ddi0380g/ +DDI0380G_smc_pl350_series_r2p1_trm.pdf + +NAND memory accesses +==================== + . Two phase NAND accesses + . NAND command phase transfers + . NAND data phase transfers + +Two phase NAND accesses + The SMC defines two phases of commands when transferring data to or from +NAND flash. + +Command phase + Commands and optional address information are written to the NAND flash. +The command and address can be associated with either a data phase operation to +write to or read from the array, or a status/ID register transfer. + +Data phase + Data is either written to or read from the NAND flash. This data can be either +data transferred to or from the array, or status/ID register information. + +NAND AXI address setup + AXI address Command phase Data phase + [31:24] Chip address Chip address + [23] NoOfAddCycles_2 Reserved + [22] NoOfAddCycles_1 Reserved + [21] NoOfAddCycles_0 ClearCS + [20] End command valid End command valid + [19] 0 1 + [18:11] End command End command + [10:3] Start command [10] ECC Last + [9:3] Reserved + [2:0] Reserved Reserved + +ECC +=== + It operates on a number of 512 byte blocks of NAND memory and can be +programmed to store the ECC codes after the data in memory. For writes, +the ECC is written to the spare area of the page. For reads, the result of +a block ECC check are made available to the device driver. + +------------------------------------------------------------------------ +| n * 512 blocks | extra | ecc | | +| | block | codes | | +------------------------------------------------------------------------ + +The ECC calculation uses a simple Hamming code, using 1-bit correction 2-bit +detection. It starts when a valid read or write command with a 512 byte aligned +address is detected on the memory interface. + +Driver details +============== + The NAND driver has dependancy with the pl353_smc memory controller +driver for intializing the nand timing parameters, bus width, ECC modes, +control and status information. + +Since the controller expects that the chipselect bit should be cleared for the +last data transfer i.e last 4 data bytes, the existing nandbase page +read/write routines for soft ecc and ecc none modes will not work. So, inorder +to make this driver work, it always updates the ecc mode as HW ECC and +implemented the page read/write functions for supporting the SW ECC. + +HW ECC mode: + Upto 2K page size is supported and beyond that it retuns +-ENOSUPPORT error. If the flsh has ONDIE ecc controller then the +priority has given to the ONDIE ecc controller. Also the current +implementation has support for upto 64 byte oob area + +SW ECC mode: + It supports all the pgae sizes. But since, zynq soc bootrom uses +HW ECC for the devices that have pgae size <=2K so, to avoid any ecc related +issues during boot, prefer HW ECC over SW ECC. + +For devicetree binding information please refer the below dt binding file +Documentation/devicetree/bindings/memory-controllers/pl353-smc.txt -- 1.7.4 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
