mtd: nand: denali: fix bank reset function to detect the number of chips

The nand_scan_ident() iterates over maxchips, and calls nand_reset()
for each.  This driver currently passes the maximum number of banks
(=chip selects) supported by the controller as maxchips.  So, maxchips
is typically 4 or 8.  Usually, less number of NAND chips are connected
to the controller.

This can be a problem for ONFi devices.  Now, this driver implements
->setup_data_interface() hook, so nand_setup_data_interface() issues
Set Features (0xEF) command, which waits until the chip returns R/B#
response.  If no chip there, we know it never happens, but the driver
still ends up with waiting for a long time.  It will finally bail-out
with timeout error and the driver will work with existing chips, but
unnecessary wait will give a bad user experience.

The denali_nand_reset() polls the INTR__RST_COMP and INTR__TIME_OUT
bits, but they are always set even if not NAND chip is connected to
that bank.  To know the chip existence, INTR__INT_ACT bit must be
checked; this flag is set only when R/B# is toggled.  Since the Reset
(0xFF) command toggles the R/B# pin, this can be used to know the
actual number of chips, and update denali->max_banks.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index 8091ba0..3169ba5 100644 (file)
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -85,33 +85,6 @@ static void index_addr(struct denali_nand_info *denali,
        iowrite32(data, denali->flash_mem + 0x10);
 }
 
-/* Reset the flash controller */
-static uint16_t denali_nand_reset(struct denali_nand_info *denali)
-{
-       int i;
-
-       for (i = 0; i < denali->max_banks; i++)
-               iowrite32(INTR__RST_COMP | INTR__TIME_OUT,
-               denali->flash_reg + INTR_STATUS(i));
-
-       for (i = 0; i < denali->max_banks; i++) {
-               iowrite32(1 << i, denali->flash_reg + DEVICE_RESET);
-               while (!(ioread32(denali->flash_reg + INTR_STATUS(i)) &
-                       (INTR__RST_COMP | INTR__TIME_OUT)))
-                       cpu_relax();
-               if (ioread32(denali->flash_reg + INTR_STATUS(i)) &
-                       INTR__TIME_OUT)
-                       dev_dbg(denali->dev,
-                       "NAND Reset operation timed out on bank %d\n", i);
-       }
-
-       for (i = 0; i < denali->max_banks; i++)
-               iowrite32(INTR__RST_COMP | INTR__TIME_OUT,
-                         denali->flash_reg + INTR_STATUS(i));
-
-       return PASS;
-}
-
 /*
  * Use the configuration feature register to determine the maximum number of
  * banks that the hardware supports.
@@ -1053,7 +1026,28 @@ static int denali_setup_data_interface(struct mtd_info *mtd, int chipnr,
        return 0;
 }
 
-/* Initialization code to bring the device up to a known good state */
+static void denali_reset_banks(struct denali_nand_info *denali)
+{
+       int i;
+
+       denali_clear_irq_all(denali);
+
+       for (i = 0; i < denali->max_banks; i++) {
+               iowrite32(1 << i, denali->flash_reg + DEVICE_RESET);
+               while (!(ioread32(denali->flash_reg + INTR_STATUS(i)) &
+                       (INTR__RST_COMP | INTR__TIME_OUT)))
+                       cpu_relax();
+               if (!(ioread32(denali->flash_reg + INTR_STATUS(i)) &
+                     INTR__INT_ACT))
+                       break;
+       }
+
+       dev_dbg(denali->dev, "%d chips connected\n", i);
+       denali->max_banks = i;
+
+       denali_clear_irq_all(denali);
+}
+
 static void denali_hw_init(struct denali_nand_info *denali)
 {
        /*
@@ -1073,7 +1067,7 @@ static void denali_hw_init(struct denali_nand_info *denali)
        denali->bbtskipbytes = ioread32(denali->flash_reg +
                                                SPARE_AREA_SKIP_BYTES);
        detect_max_banks(denali);
-       denali_nand_reset(denali);
+       denali_reset_banks(denali);
        iowrite32(0x0F, denali->flash_reg + RB_PIN_ENABLED);
        iowrite32(CHIP_EN_DONT_CARE__FLAG,
                        denali->flash_reg + CHIP_ENABLE_DONT_CARE);