[PATCH v7 15/28] mtd: rawnand: timings: Add a helper to find the closest ONFI mode

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

Vendors are allowed to provide their own set of timings. In this case,
we provide a way to derive the "closest" timing mode so that, if the
NAND controller does not support tweaking these parameters, it will be
able to configure itself anyway.

Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
---
 drivers/mtd/nand/raw/internals.h    |  2 ++
 drivers/mtd/nand/raw/nand_timings.c | 47 +++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/mtd/nand/raw/internals.h b/drivers/mtd/nand/raw/internals.h
index bd10ec92f04a..f851ed210d70 100644
--- a/drivers/mtd/nand/raw/internals.h
+++ b/drivers/mtd/nand/raw/internals.h
@@ -88,6 +88,8 @@ int onfi_fill_data_interface(struct nand_chip *chip,
 			     struct nand_data_interface *iface,
 			     enum nand_data_interface_type type,
 			     unsigned int timing_mode);
+unsigned int
+onfi_find_closest_sdr_mode(const struct nand_sdr_timings *spec_timings);
 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_timings.c b/drivers/mtd/nand/raw/nand_timings.c
index 08dc381349fa..b089f2dc5f23 100644
--- a/drivers/mtd/nand/raw/nand_timings.c
+++ b/drivers/mtd/nand/raw/nand_timings.c
@@ -273,6 +273,53 @@ static const struct nand_data_interface onfi_sdr_timings[] = {
 	},
 };
 
+/**
+ * onfi_find_closest_sdr_mode - Derive the closest ONFI SDR timing mode given a
+ *                              set of timings
+ * @spec_timings: the timings to challenge
+ */
+unsigned int
+onfi_find_closest_sdr_mode(const struct nand_sdr_timings *spec_timings)
+{
+	const struct nand_sdr_timings *onfi_timings;
+	int mode;
+
+	for (mode = ARRAY_SIZE(onfi_sdr_timings) - 1; mode > 0; mode--) {
+		onfi_timings = &onfi_sdr_timings[mode].timings.sdr;
+
+		if (spec_timings->tCCS_min <= onfi_timings->tCCS_min &&
+		    spec_timings->tADL_min <= onfi_timings->tADL_min &&
+		    spec_timings->tALH_min <= onfi_timings->tALH_min &&
+		    spec_timings->tALS_min <= onfi_timings->tALS_min &&
+		    spec_timings->tAR_min <= onfi_timings->tAR_min &&
+		    spec_timings->tCEH_min <= onfi_timings->tCEH_min &&
+		    spec_timings->tCH_min <= onfi_timings->tCH_min &&
+		    spec_timings->tCLH_min <= onfi_timings->tCLH_min &&
+		    spec_timings->tCLR_min <= onfi_timings->tCLR_min &&
+		    spec_timings->tCLS_min <= onfi_timings->tCLS_min &&
+		    spec_timings->tCOH_min <= onfi_timings->tCOH_min &&
+		    spec_timings->tCS_min <= onfi_timings->tCS_min &&
+		    spec_timings->tDH_min <= onfi_timings->tDH_min &&
+		    spec_timings->tDS_min <= onfi_timings->tDS_min &&
+		    spec_timings->tIR_min <= onfi_timings->tIR_min &&
+		    spec_timings->tRC_min <= onfi_timings->tRC_min &&
+		    spec_timings->tREH_min <= onfi_timings->tREH_min &&
+		    spec_timings->tRHOH_min <= onfi_timings->tRHOH_min &&
+		    spec_timings->tRHW_min <= onfi_timings->tRHW_min &&
+		    spec_timings->tRLOH_min <= onfi_timings->tRLOH_min &&
+		    spec_timings->tRP_min <= onfi_timings->tRP_min &&
+		    spec_timings->tRR_min <= onfi_timings->tRR_min &&
+		    spec_timings->tWC_min <= onfi_timings->tWC_min &&
+		    spec_timings->tWH_min <= onfi_timings->tWH_min &&
+		    spec_timings->tWHR_min <= onfi_timings->tWHR_min &&
+		    spec_timings->tWP_min <= onfi_timings->tWP_min &&
+		    spec_timings->tWW_min <= onfi_timings->tWW_min)
+			return mode;
+	}
+
+	return 0;
+}
+
 /**
  * onfi_fill_data_interface - Initialize a data interface from a given ONFI mode
  * @chip: The NAND chip
-- 
2.20.1


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