[RFC PATCH 2/2] gpmi-nand: Add ERR007117 protection for nfc_apply_timings

[Stefan Riedmueller]

According to i.MX 6 erratum ERR007117 gpmi clocks need to be gated off
when doing a gpmi_io clk rate change. So gate the clocks off before
the rate change in nfc_apply_timings and ungate them again after the
change.

Otherwise this rate change can lead to an unresponsive GPMI core which
results in DMA timeouts and failed driver probe:

[    4.072318] gpmi-nand 112000.gpmi-nand: DMA timeout, last DMA
...
[    4.370355] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -110
...
[    4.375988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
[    4.381524] gpmi-nand 112000.gpmi-nand: Error in ECC-based read: -22
[    4.387988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
[    4.393535] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
...

Signed-off-by: Stefan Riedmueller <s.riedmueller at phytec.de>
---
Hi,

I'm not sure about the error handling here, if it is actually neccessary.
So some feedback would be nice here.

Thanks,
Stefan
---
 drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
index a1f7000f033e..326c8a895f1f 100644
--- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
@@ -713,15 +713,28 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
 			      (use_half_period ? BM_GPMI_CTRL1_HALF_PERIOD : 0);
 }
 
-static void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
+static int gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
 {
 	struct gpmi_nfc_hardware_timing *hw = &this->hw;
 	struct resources *r = &this->resources;
 	void __iomem *gpmi_regs = r->gpmi_regs;
 	unsigned int dll_wait_time_us;
+	int ret;
+
+	if (GPMI_IS_MX6Q(this)) {
+		ret = __gpmi_enable_clk(this, false);
+		if (ret)
+			return ret;
+	}
 
 	clk_set_rate(r->clock[0], hw->clk_rate);
 
+	if (GPMI_IS_MX6Q(this)) {
+		ret = __gpmi_enable_clk(this, true);
+		if (ret)
+			return ret;
+	}
+
 	writel(hw->timing0, gpmi_regs + HW_GPMI_TIMING0);
 	writel(hw->timing1, gpmi_regs + HW_GPMI_TIMING1);
 
@@ -739,6 +752,8 @@ static void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
 
 	/* Wait for the DLL to settle. */
 	udelay(dll_wait_time_us);
+
+	return 0;
 }
 
 static int gpmi_setup_interface(struct nand_chip *chip, int chipnr,
@@ -2271,7 +2286,9 @@ static int gpmi_nfc_exec_op(struct nand_chip *chip,
 	 */
 	if (this->hw.must_apply_timings) {
 		this->hw.must_apply_timings = false;
-		gpmi_nfc_apply_timings(this);
+		ret = gpmi_nfc_apply_timings(this);
+		if (ret)
+			return ret;
 	}
 
 	dev_dbg(this->dev, "%s: %d instructions\n", __func__, op->ninstrs);
-- 
2.25.1