mmc: rtsx_pci_sdmmc: implement sdmmc_card_busy function

rtsx_pci_sdmmc does not have an sdmmc_card_busy function, so any voltage
switches cause a kernel warning, "mmc0: cannot verify signal voltage
switch."

Copy the sdmmc_card_busy function from rtsx_pci_usb to rtsx_pci_sdmmc to
fix this.

Fixes: ff984e5 ("mmc: Add realtek pcie sdmmc host driver")
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
Tested-by: Ricky WU <ricky_wu@realtek.com>
Reviewed-by: Ricky WU <ricky_wu@realtek.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: matte-schwartz

drivers/mmc/host/rtsx_pci_sdmmc.c

@@ -1306,6 +1306,46 @@ static int sdmmc_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
 	return err;
 }
 
+static int sdmmc_card_busy(struct mmc_host *mmc)
+{
+	struct realtek_pci_sdmmc *host = mmc_priv(mmc);
+	struct rtsx_pcr *pcr = host->pcr;
+	int err;
+	u8 stat;
+	u8 mask = SD_DAT3_STATUS | SD_DAT2_STATUS | SD_DAT1_STATUS
+	| SD_DAT0_STATUS;
+
+	mutex_lock(&pcr->pcr_mutex);
+
+	rtsx_pci_start_run(pcr);
+
+	err = rtsx_pci_write_register(pcr, SD_BUS_STAT,
+				      SD_CLK_TOGGLE_EN | SD_CLK_FORCE_STOP,
+			       SD_CLK_TOGGLE_EN);
+	if (err)
+		goto out;
+
+	mdelay(1);
+
+	err = rtsx_pci_read_register(pcr, SD_BUS_STAT, &stat);
+	if (err)
+		goto out;
+
+	err = rtsx_pci_write_register(pcr, SD_BUS_STAT,
+				      SD_CLK_TOGGLE_EN | SD_CLK_FORCE_STOP, 0);
+out:
+	mutex_unlock(&pcr->pcr_mutex);
+
+	if (err)
+		return err;
+
+	/* check if any pin between dat[0:3] is low */
+	if ((stat & mask) != mask)
+		return 1;
+	else
+		return 0;
+}
+
 static int sdmmc_execute_tuning(struct mmc_host *mmc, u32 opcode)
 {
 	struct realtek_pci_sdmmc *host = mmc_priv(mmc);
@@ -1418,6 +1458,7 @@ static const struct mmc_host_ops realtek_pci_sdmmc_ops = {
 	.get_ro = sdmmc_get_ro,
 	.get_cd = sdmmc_get_cd,
 	.start_signal_voltage_switch = sdmmc_switch_voltage,
+	.card_busy = sdmmc_card_busy,
 	.execute_tuning = sdmmc_execute_tuning,
 	.init_sd_express = sdmmc_init_sd_express,
 };