[PATCH v2] mtd: rawnand: hynix: fix up bit 0 of sdr_timing_mode

[Hector Palacios]

According to the ONFI specification, bit 0 of 'SDR timing mode support'
(bytes 129-130) "shall be 1". That means the NAND supports at least
timing mode 0.

NAND chip Hynix H27U4G8F2GDA-BI (at least) is reading a 0 on this field
which makes nand_choose_best_sdr_timings() return with error and the
probe function to eventually fail.

Given that sdr_timing_modes bit 0 must be 1 by specification, force
it in case the NAND reports it is not set. This is a safe assumption
because the mode 0 is the minimum (safer) set of timings that the
NAND can work with.

Signed-off-by: Hector Palacios <hector.palacios at digi.com>
---
v2:
  Move patch to Hynix specific fixup hook.
  Use BIT(0) macro.
v1:
  Implement generic patch in nand_base.c.

 drivers/mtd/nand/raw/nand_hynix.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_hynix.c b/drivers/mtd/nand/raw/nand_hynix.c
index 0d4d4bbfdece..93f97290e3ce 100644
--- a/drivers/mtd/nand/raw/nand_hynix.c
+++ b/drivers/mtd/nand/raw/nand_hynix.c
@@ -728,8 +728,22 @@ static int hynix_nand_init(struct nand_chip *chip)
 	return ret;
 }
 
+static void hynix_fixup_onfi_param_page(struct nand_chip *chip,
+					struct nand_onfi_params *p)
+{
+	/*
+	 * Certain chips might report a 0 on sdr_timing_mode field
+	 * (bytes 129-130). This has been seen on H27U4G8F2GDA-BI.
+	 * According to ONFI specification, bit 0 of this field "shall be 1".
+	 * Force this bit if unset.
+	 */
+	if (!(p->sdr_timing_modes && BIT(0)))
+		p->sdr_timing_modes |= BIT(0);
+}
+
 const struct nand_manufacturer_ops hynix_nand_manuf_ops = {
 	.detect = hynix_nand_decode_id,
 	.init = hynix_nand_init,
 	.cleanup = hynix_nand_cleanup,
+	.fixup_onfi_param_page = hynix_fixup_onfi_param_page,
 };