`mt7621_nfc_write_page_hwecc` may be called with `buf=NULL`, but
`mt7621_nfc_check_empty_page` always tries to read it.
That caused Oops:
`Unable to handle kernel paging request at virtual address
00000000`
Fixes: FS#3416
Signed-off-by: Anton Ryzhov <anton@ryzhov.me>
obj-$(CONFIG_MTD_NAND_TEGRA) += tegra_nand.o
--- /dev/null
+++ b/drivers/mtd/nand/raw/mt7621_nand.c
-@@ -0,0 +1,1348 @@
+@@ -0,0 +1,1350 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MediaTek MT7621 NAND Flash Controller driver
+ uint32_t i, j;
+ u8 *oobptr;
+
-+ for (i = 0; i < mtd->writesize; i++)
-+ if (buf[i] != 0xff)
-+ return 0;
++ if (buf) {
++ for (i = 0; i < mtd->writesize; i++)
++ if (buf[i] != 0xff)
++ return 0;
++ }
+
+ for (i = 0; i < nand->ecc.steps; i++) {
+ oobptr = oob_fdm_ptr(nand, i);