diff --git a/drivers/mmc/core/card.h b/drivers/mmc/core/card.h
index a36cda051d160c..1a9c8fa5adb775 100644
--- a/drivers/mmc/core/card.h
+++ b/drivers/mmc/core/card.h
@@ -90,8 +90,10 @@ struct mmc_fixup {
 #define CID_MANFID_SAMSUNG      0x15
 #define CID_MANFID_SAMSUNG_SD	0x1b
 #define CID_MANFID_APACER       0x27
+#define CID_MANFID_BIWIN_SD	0x4E
 #define CID_MANFID_SWISSBIT     0x5D
 #define CID_MANFID_KINGSTON     0x70
+#define CID_MANFID_TRANSCEND_SD	0x74
 #define CID_MANFID_HYNIX	0x90
 #define CID_MANFID_KINGSTON_SD	0x9F
 #define CID_MANFID_LONGSYS_SD	0xAD
diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h
index f23319a5fb79bc..8ea9b0248490e4 100644
--- a/drivers/mmc/core/quirks.h
+++ b/drivers/mmc/core/quirks.h
@@ -76,6 +76,16 @@ static const struct mmc_fixup __maybe_unused mmc_sd_fixups[] = {
 		   0, -1ull, SDIO_ANY_ID, SDIO_ANY_ID, add_quirk_sd,
 		   MMC_QUIRK_BROKEN_SD_CACHE, EXT_CSD_REV_ANY),
 
+	/* Transcend cards need a CMD49 workaround */
+	_FIXUP_EXT("USDU1", CID_MANFID_TRANSCEND_SD, 0x4a60, CID_YEAR_ANY, CID_MONTH_ANY,
+		   cid_rev(2, 0, 0, 0), -1ull, SDIO_ANY_ID, SDIO_ANY_ID, add_quirk_sd,
+		   MMC_QUIRK_NONSTD_SD_CMD49, EXT_CSD_REV_ANY),
+
+	/* Certain Biwin cards need a CMD49 workaround */
+	_FIXUP_EXT("SMI  ", CID_MANFID_BIWIN_SD, 0x4257, CID_YEAR_ANY, CID_MONTH_ANY,
+		   cid_rev(1, 0, 2025, 0), -1ull, SDIO_ANY_ID, SDIO_ANY_ID, add_quirk_sd,
+		   MMC_QUIRK_NONSTD_SD_CMD49, EXT_CSD_REV_ANY),
+
 	/* SD A2 allow-list - only trust CQ on these cards */
 	/* Raspberry Pi A2 cards */
 	_FIXUP_EXT(CID_NAME_ANY, CID_MANFID_LONGSYS_SD, 0x4c53, CID_YEAR_ANY, CID_MONTH_ANY,
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 551553a44d9784..fe45adfcafb286 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -1218,6 +1218,26 @@ static int mmc_sd_read_ext_regs(struct mmc_card *card)
 		goto out;
 	}
 
+	/* Some cards have zeroes in GEN_INFO but correctly implement EXT_PERF and EXT_PWR */
+	if (!memcmp(card->ext_reg_buf, gen_info_buf, 512)) {
+		pr_info("%s: using fall-back extension register parsing\n",
+			mmc_hostname(card->host));
+		/* PWR typically hard-coded at FNO=1 */
+		err = sd_parse_ext_reg_power(card, 1, 0, 0);
+		if (err) {
+			pr_err("%s: error %d parsing SD Power extension\n",
+				mmc_hostname(card->host), err);
+			goto out;
+		}
+		/* PERF typically hard-coded at FNO=2 */
+		err = sd_parse_ext_reg_perf(card, 2, 0, 0);
+		if (err) {
+			pr_err("%s: error %d parsing SD Performance extension\n",
+			       mmc_hostname(card->host), err);
+		}
+		goto out;
+	}
+
 	/* General info structure revision. */
 	memcpy(&rev, &gen_info_buf[0], 2);
 
diff --git a/drivers/mmc/core/sd_ops.c b/drivers/mmc/core/sd_ops.c
index 47a1903268b2e0..4f11be42d9636d 100644
--- a/drivers/mmc/core/sd_ops.c
+++ b/drivers/mmc/core/sd_ops.c
@@ -421,10 +421,23 @@ int mmc_sd_write_ext_reg(struct mmc_card *card, u8 fno, u8 page, u16 offset,
 	 * [17:9] offset address.
 	 * [8:0] length (0 = 1 byte).
 	 */
-	cmd.arg = fno << 27 | page << 18 | offset << 9;
+	if (card->quirks & MMC_QUIRK_NONSTD_SD_CMD49) {
+		int err;
+		/*
+		 * Card ignores length/offset and always applies
+		 * all 512B of the write data block. RmW cycle required.
+		 */
+		err = mmc_sd_read_ext_reg(card, fno, page, 0, 512, reg_buf);
+		if (err)
+			return err;
 
-	/* The first byte in the buffer is the data to be written. */
-	reg_buf[0] = reg_data;
+		cmd.arg = fno << 27 | page << 18;
+		reg_buf[offset] = reg_data;
+	} else {
+		cmd.arg = fno << 27 | page << 18 | offset << 9;
+		/* The first byte in the buffer is the data to be written. */
+		reg_buf[0] = reg_data;
+	}
 
 	data.flags = MMC_DATA_WRITE;
 	data.blksz = 512;
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index a6c766c157bd54..eeb6a39200c25e 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -296,6 +296,7 @@ struct mmc_card {
 #define MMC_QUIRK_BROKEN_CACHE_FLUSH	(1<<16)	/* Don't flush cache until the write has occurred */
 #define MMC_QUIRK_BROKEN_SD_POWEROFF_NOTIFY	(1<<17) /* Disable broken SD poweroff notify support */
 #define MMC_QUIRK_NO_UHS_DDR50_TUNING	(1<<18) /* Disable DDR50 tuning */
+#define MMC_QUIRK_NONSTD_SD_CMD49	(1<<29)	/* SD card ignores length/offset argument */
 #define MMC_QUIRK_WORKING_SD_CQ	(1<<30)		/* SD card has known-good CQ implementation */
 #define MMC_QUIRK_ERASE_BROKEN	(1<<31)		/* Skip erase */