mtd: nand: pl35x: Implement De-select in Chip Select which saves power

nand_select_chip when called with negative chip no.
means we have finished operations on the chip
so we can deselect it. This allows the chip to
enter a lower power state.

Signed-off-by: Andrew Worsley <amworsley@gmail.com>
Reviewed-by: Naga Sureshkumar Relli <naga.sureshkumar.relli@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --git a/drivers/mtd/nand/pl35x_nand.c b/drivers/mtd/nand/pl35x_nand.c
index e8329a297f5cf75856aae15e5c17f3c677887c38..2d9c396864ce8d6a580012a4a10668e817c626dd 100644 (file)
--- a/drivers/mtd/nand/pl35x_nand.c
+++ b/drivers/mtd/nand/pl35x_nand.c
@@ -766,14 +766,34 @@ static int pl35x_nand_read_page_swecc(struct mtd_info *mtd,
 /**
  * pl35x_nand_select_chip - Select the flash device
  * @mtd:       Pointer to the mtd info structure
- * @chip:      Pointer to the NAND chip info structure
+ * @chipnr:    chipnumber to select, -1 for deselect
  *
  * This function is empty as the NAND controller handles chip select line
  * internally based on the chip address passed in command and data phase.
  */
-static void pl35x_nand_select_chip(struct mtd_info *mtd, int chip)
+static void pl35x_nand_select_chip(struct mtd_info *mtd, int chipnr)
 {
-       return;
+       unsigned long data_phase_addr;
+       struct pl35x_nand_info *xnand;
+       unsigned long nand_offset;
+       struct nand_chip *chip;
+
+       /*
+        * Chip selection will happen in command/data operation
+        */
+       if (chipnr >= 0)
+               return;
+
+       /* de-assert chip select */
+       chip = mtd_to_nand(mtd);
+       data_phase_addr = (unsigned long __force)chip->IO_ADDR_R;
+       xnand = container_of(chip, struct pl35x_nand_info, chip);
+       nand_offset = (unsigned long __force)xnand->nand_base;
+       data_phase_addr -= nand_offset;
+       data_phase_addr |= PL35X_NAND_CLEAR_CS;
+       data_phase_addr += nand_offset;
+       chip->IO_ADDR_R = (void __iomem * __force)data_phase_addr;
+       chip->read_byte(mtd);
 }
 
 /**