ONFI timing mode with onfi_set_features unsupported

[Sascha Hauer]

Hi all,

I have a i.MX6ul here with a Cypress S34ML04G2 connected. This Nand chip
has ONFI support, but onfi_set_features is unsupported (opt_cmd is
0x3b). Currently the gpmi Nand driver calls nand_onfi_set_features(),
gets -EINVAL as error and continues with a very slow default timing.

I assume the nand_onfi_set_features() call is just unnecessary for this
chip, if I skip it, the chip works with the fast timing.

Any idea how to cope with this situation? I attached the most obvious
patch, but it looks a bit hackish. Any suggestions or is the patch fine
as is?

Sascha


---------------------------------8<----------------------------

>From 1d76ea80915b298b99def706cac0e20b65bd7ef4 Mon Sep 17 00:00:00 2001
From: Sascha Hauer <s.hauer at pengutronix.de>
Date: Mon, 21 Nov 2016 14:18:27 +0100
Subject: [PATCH] mtd: nand: gpmi: Fix timing on ONFI chips with
 onfi_set_features unsupported

Some chips like for example the Cypress S34ML04G2 are ONFI compliant,
but do not support the get/set_feature commands. Do not call this
command when it's not supported to allow for a fast timing on these
chips.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
index 141bd70..7b2862c 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
@@ -930,23 +930,26 @@ static int enable_edo_mode(struct gpmi_nand_data *this, int mode)
 	if (!feature)
 		return -ENOMEM;
 
-	nand->select_chip(mtd, 0);
+	if ((le16_to_cpu(nand->onfi_params.opt_cmd)
+	      & ONFI_OPT_CMD_SET_GET_FEATURES)) {
+		nand->select_chip(mtd, 0);
 
-	/* [1] send SET FEATURE commond to NAND */
-	feature[0] = mode;
-	ret = nand->onfi_set_features(mtd, nand,
+		/* [1] send SET FEATURE commond to NAND */
+		feature[0] = mode;
+		ret = nand->onfi_set_features(mtd, nand,
 				ONFI_FEATURE_ADDR_TIMING_MODE, feature);
-	if (ret)
-		goto err_out;
+		if (ret)
+			goto err_out;
 
-	/* [2] send GET FEATURE command to double-check the timing mode */
-	memset(feature, 0, ONFI_SUBFEATURE_PARAM_LEN);
-	ret = nand->onfi_get_features(mtd, nand,
+		/* [2] send GET FEATURE command to double-check the timing mode */
+		memset(feature, 0, ONFI_SUBFEATURE_PARAM_LEN);
+		ret = nand->onfi_get_features(mtd, nand,
 				ONFI_FEATURE_ADDR_TIMING_MODE, feature);
-	if (ret || feature[0] != mode)
-		goto err_out;
+		if (ret || feature[0] != mode)
+			goto err_out;
 
-	nand->select_chip(mtd, -1);
+		nand->select_chip(mtd, -1);
+	}
 
 	/* [3] set the main IO clock, 100MHz for mode 5, 80MHz for mode 4. */
 	rate = (mode == 5) ? 100000000 : 80000000;
-- 
2.10.2

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