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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=f486287d2372422d68768c88fe54e80a48aee8ec
Commit:     f486287d2372422d68768c88fe54e80a48aee8ec
Parent:     fa6134e5457d3177b82b35fa4004505f2571150a
Author:     Masahiro Yamada <yamada.masahiro at socionext.com>
AuthorDate: Tue Jun 13 22:45:40 2017 +0900
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Tue Jun 20 09:14:34 2017 +0200

    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 at socionext.com>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/nand/denali.c | 52 +++++++++++++++++++++--------------------------
 1 file changed, 23 insertions(+), 29 deletions(-)

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index 8091ba0..3169ba5 100644
--- 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);