linux-kernel - [PATCH] mmc: rtsx_pci_sdmmc: simplify voltage switch handling after card

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20260130030501.373630-1-ricky_wu@realtek.com>
Date: Fri, 30 Jan 2026 11:05:01 +0800
From: <ricky_wu@...ltek.com>
To: <ricky_wu@...ltek.com>, <ulf.hansson@...aro.org>,
        <matthew.schwartz@...ux.dev>, <linux-mmc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] mmc: rtsx_pci_sdmmc: simplify voltage switch handling after card_busy()

From: Ricky Wu <ricky_wu@...ltek.com>

Now that the Realtek PCIe SDMMC host implements the card_busy() callback,
the MMC core performs the required DAT[3:0] validation during the signal
voltage switch sequence.

As a result, the driver-side voltage stabilization helpers
sd_wait_voltage_stable_1() and sd_wait_voltage_stable_2() become redundant.
These helpers duplicate DAT line checks that are now handled centrally by
the MMC core via card_busy().

Remove the two stabilization helpers and simplify sdmmc_switch_voltage()
accordingly, keeping only the minimal clock control needed around the
voltage switch.

No functional changes and intended.

Signed-off-by: Ricky Wu <ricky_wu@...ltek.com>
---
 drivers/mmc/host/rtsx_pci_sdmmc.c | 88 +++----------------------------
 1 file changed, 6 insertions(+), 82 deletions(-)

diff --git a/drivers/mmc/host/rtsx_pci_sdmmc.c b/drivers/mmc/host/rtsx_pci_sdmmc.c
index 4db3328f46df..8dfbc62f165b 100644
--- a/drivers/mmc/host/rtsx_pci_sdmmc.c
+++ b/drivers/mmc/host/rtsx_pci_sdmmc.c
@@ -1181,79 +1181,6 @@ static int sdmmc_get_cd(struct mmc_host *mmc)
 	return cd;
 }
 
-static int sd_wait_voltage_stable_1(struct realtek_pci_sdmmc *host)
-{
-	struct rtsx_pcr *pcr = host->pcr;
-	int err;
-	u8 stat;
-
-	/* Reference to Signal Voltage Switch Sequence in SD spec.
-	 * Wait for a period of time so that the card can drive SD_CMD and
-	 * SD_DAT[3:0] to low after sending back CMD11 response.
-	 */
-	mdelay(1);
-
-	/* SD_CMD, SD_DAT[3:0] should be driven to low by card;
-	 * If either one of SD_CMD,SD_DAT[3:0] is not low,
-	 * abort the voltage switch sequence;
-	 */
-	err = rtsx_pci_read_register(pcr, SD_BUS_STAT, &stat);
-	if (err < 0)
-		return err;
-
-	if (stat & (SD_CMD_STATUS | SD_DAT3_STATUS | SD_DAT2_STATUS |
-				SD_DAT1_STATUS | SD_DAT0_STATUS))
-		return -EINVAL;
-
-	/* Stop toggle SD clock */
-	err = rtsx_pci_write_register(pcr, SD_BUS_STAT,
-			0xFF, SD_CLK_FORCE_STOP);
-	if (err < 0)
-		return err;
-
-	return 0;
-}
-
-static int sd_wait_voltage_stable_2(struct realtek_pci_sdmmc *host)
-{
-	struct rtsx_pcr *pcr = host->pcr;
-	int err;
-	u8 stat, mask, val;
-
-	/* Wait 1.8V output of voltage regulator in card stable */
-	msleep(50);
-
-	/* Toggle SD clock again */
-	err = rtsx_pci_write_register(pcr, SD_BUS_STAT, 0xFF, SD_CLK_TOGGLE_EN);
-	if (err < 0)
-		return err;
-
-	/* Wait for a period of time so that the card can drive
-	 * SD_DAT[3:0] to high at 1.8V
-	 */
-	msleep(20);
-
-	/* SD_CMD, SD_DAT[3:0] should be pulled high by host */
-	err = rtsx_pci_read_register(pcr, SD_BUS_STAT, &stat);
-	if (err < 0)
-		return err;
-
-	mask = SD_CMD_STATUS | SD_DAT3_STATUS | SD_DAT2_STATUS |
-		SD_DAT1_STATUS | SD_DAT0_STATUS;
-	val = SD_CMD_STATUS | SD_DAT3_STATUS | SD_DAT2_STATUS |
-		SD_DAT1_STATUS | SD_DAT0_STATUS;
-	if ((stat & mask) != val) {
-		dev_dbg(sdmmc_dev(host),
-			"%s: SD_BUS_STAT = 0x%x\n", __func__, stat);
-		rtsx_pci_write_register(pcr, SD_BUS_STAT,
-				SD_CLK_TOGGLE_EN | SD_CLK_FORCE_STOP, 0);
-		rtsx_pci_write_register(pcr, CARD_CLK_EN, 0xFF, 0);
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
 static int sdmmc_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 	struct realtek_pci_sdmmc *host = mmc_priv(mmc);
@@ -1281,7 +1208,9 @@ static int sdmmc_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
 		voltage = OUTPUT_1V8;
 
 	if (voltage == OUTPUT_1V8) {
-		err = sd_wait_voltage_stable_1(host);
+		/* Stop toggle SD clock */
+		err = rtsx_pci_write_register(pcr, SD_BUS_STAT,
+				0xFF, SD_CLK_FORCE_STOP);
 		if (err < 0)
 			goto out;
 	}
@@ -1290,16 +1219,11 @@ static int sdmmc_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
 	if (err < 0)
 		goto out;
 
-	if (voltage == OUTPUT_1V8) {
-		err = sd_wait_voltage_stable_2(host);
-		if (err < 0)
-			goto out;
-	}
-
 out:
 	/* Stop toggle SD clock in idle */
-	err = rtsx_pci_write_register(pcr, SD_BUS_STAT,
-			SD_CLK_TOGGLE_EN | SD_CLK_FORCE_STOP, 0);
+	if (err < 0)
+		rtsx_pci_write_register(pcr, SD_BUS_STAT,
+				SD_CLK_TOGGLE_EN | SD_CLK_FORCE_STOP, 0);
 
 	mutex_unlock(&pcr->pcr_mutex);
 
-- 
2.25.1