mtd: cfi_cmdset_0002: Use chip_ready() for write on S29GL064N

Since commit dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to
check correct value") buffered writes fail on S29GL064N. This is
because, on S29GL064N, reads return 0xFF at the end of DQ polling for
write completion, where as, chip_good() check expects actual data
written to the last location to be returned post DQ polling completion.
Fix is to revert to using chip_good() for S29GL064N which only checks
for DQ lines to settle down to determine write completion.

Link: https://lore.kernel.org/r/[e-mail]/
Fixes: dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to check correct value")
Cc: [e-mail]
Signed-off-by: Tokunori Ikegami <[e-mail]>
Acked-by: Vignesh Raghavendra <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

drivers/mtd/chips/cfi_cmdset_0002.c

···
 #define CFI_SR_WBASB		BIT(3)
 #define CFI_SR_SLSB		BIT(1)
 
+enum cfi_quirks {
+	CFI_QUIRK_DQ_TRUE_DATA = BIT(0),
+};
+
 static int cfi_amdstd_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
 static int cfi_amdstd_write_words(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
 #if !FORCE_WORD_WRITE
···
 		mtd->name);
 }
 
+static void fixup_quirks(struct mtd_info *mtd)
+{
+	struct map_info *map = mtd->priv;
+	struct cfi_private *cfi = map->fldrv_priv;
+
+	if (cfi->mfr == CFI_MFR_AMD && cfi->id == 0x0c01)
+		cfi->quirks |= CFI_QUIRK_DQ_TRUE_DATA;
+}
+
 /* Used to fix CFI-Tables of chips without Extended Query Tables */
 static struct cfi_fixup cfi_nopri_fixup_table[] = {
 	{ CFI_MFR_SST, 0x234a, fixup_sst39vf }, /* SST39VF1602 */
···
 #if !FORCE_WORD_WRITE
 	{ CFI_MFR_ANY, CFI_ID_ANY, fixup_use_write_buffers },
 #endif
+	{ CFI_MFR_ANY, CFI_ID_ANY, fixup_quirks },
 	{ 0, 0, NULL }
 };
 static struct cfi_fixup jedec_fixup_table[] = {
···
 		return ret;
 
 	return map_word_equal(map, t, *expected);
+}
+
+static int __xipram chip_good(struct map_info *map, struct flchip *chip,
+			      unsigned long addr, map_word *expected)
+{
+	struct cfi_private *cfi = map->fldrv_priv;
+	map_word *datum = expected;
+
+	if (cfi->quirks & CFI_QUIRK_DQ_TRUE_DATA)
+		datum = NULL;
+
+	return chip_ready(map, chip, addr, datum);
 }
 
 static int get_chip(struct map_info *map, struct flchip *chip, unsigned long adr, int mode)
···
 		}
 
 		/*
-		 * We check "time_after" and "!chip_ready" before checking
-		 * "chip_ready" to avoid the failure due to scheduling.
+		 * We check "time_after" and "!chip_good" before checking
+		 * "chip_good" to avoid the failure due to scheduling.
 		 */
 		if (time_after(jiffies, timeo) &&
-		    !chip_ready(map, chip, adr, &datum)) {
+		    !chip_good(map, chip, adr, &datum)) {
 			xip_enable(map, chip, adr);
 			printk(KERN_WARNING "MTD %s(): software timeout\n", __func__);
 			xip_disable(map, chip, adr);
···
 			break;
 		}
 
-		if (chip_ready(map, chip, adr, &datum)) {
+		if (chip_good(map, chip, adr, &datum)) {
 			if (cfi_check_err_status(map, chip, adr))
 				ret = -EIO;
 			break;
···
 		}
 
 		/*
-		 * We check "time_after" and "!chip_ready" before checking
-		 * "chip_ready" to avoid the failure due to scheduling.
+		 * We check "time_after" and "!chip_good" before checking
+		 * "chip_good" to avoid the failure due to scheduling.
 		 */
 		if (time_after(jiffies, timeo) &&
-		    !chip_ready(map, chip, adr, &datum)) {
+		    !chip_good(map, chip, adr, &datum)) {
 			pr_err("MTD %s(): software timeout, address:0x%.8lx.\n",
 			       __func__, adr);
 			ret = -EIO;
 			break;
 		}
 
-		if (chip_ready(map, chip, adr, &datum)) {
+		if (chip_good(map, chip, adr, &datum)) {
 			if (cfi_check_err_status(map, chip, adr))
 				ret = -EIO;
 			break;

include/linux/mtd/cfi.h

···
 	map_word sector_erase_cmd;
 	unsigned long chipshift; /* Because they're of the same type */
 	const char *im_name;	 /* inter_module name for cmdset_setup */
+	unsigned long quirks;
 	struct flchip chips[];  /* per-chip data structure for each chip */
 };