[PATCH v4 17/19] mtd: rawnand: Introduce nand_choose_best_vendor_sdr_iface()

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

This helper is here to simplify the life of NAND manufacturer drivers.

Manufacturers will be allowed to propose their own set of timings and,
if they want, use this helper to:
1/ verify it is supported by the controller,
2/ fallback on a supported default ONFI mode, slower but still faster
   than the default mode 0.

Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
 drivers/mtd/nand/raw/internals.h |  2 ++
 drivers/mtd/nand/raw/nand_base.c | 27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/mtd/nand/raw/internals.h b/drivers/mtd/nand/raw/internals.h
index ac103d8767be..9af6979257e2 100644
--- a/drivers/mtd/nand/raw/internals.h
+++ b/drivers/mtd/nand/raw/internals.h
@@ -89,6 +89,8 @@ int onfi_fill_data_interface(struct nand_chip *chip,
 			     enum nand_data_interface_type type,
 			     int timing_mode);
 unsigned int onfi_find_equivalent_sdr_mode(const struct nand_sdr_timings *vendor_timings);
+int nand_choose_best_vendor_sdr_iface(struct nand_chip * chip,
+				      struct nand_data_interface *best_iface);
 int nand_get_features(struct nand_chip *chip, int addr, u8 *subfeature_param);
 int nand_set_features(struct nand_chip *chip, int addr, u8 *subfeature_param);
 int nand_read_page_raw_notsupp(struct nand_chip *chip, u8 *buf,
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 15e10f045c9f..d9fe7795f183 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -1078,6 +1078,33 @@ static int nand_choose_data_interface(struct nand_chip *chip)
 	return nand_choose_best_sdr_iface(chip, &chip->data_interface);
 }
 
+/**
+ * nand_choose_best_vendor_sdr_iface - given a set of timings, find the closest
+ *                                     mode/timings set for this interface
+ *                                     supported by both the NAND controller and
+ *                                     the NAND chip
+ * @chip: the NAND chip
+ * @best_iface: the best data interface (can eventually be updated)
+ */
+int nand_choose_best_vendor_sdr_iface(struct nand_chip * chip,
+				      struct nand_data_interface *best_iface)
+{
+	int ret;
+
+	/* Pick the closest mode */
+	best_iface->timings.mode = onfi_find_equivalent_sdr_mode(&best_iface->timings.sdr);
+
+	/* Find the closest supported data interface */
+	ret = nand_choose_best_sdr_iface(chip, best_iface);
+	if (ret)
+		return ret;
+
+	chip->data_interface = *best_iface;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nand_choose_best_vendor_sdr_iface);
+
 /**
  * nand_fill_column_cycles - fill the column cycles of an address
  * @chip: The NAND chip
-- 
2.20.1


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