misc: rtsx: usb card reader: add OCP support

This patch adds support for Over Current Protection (OCP) to the Realtek
USB card reader driver.

The OCP mechanism protects the hardware by detecting and handling current
overload conditions.
This implementation includes:

- Register configurations to enable OCP monitoring.
- Handling of OCP interrupt events and associated error reporting.
- Card power management changes in response to OCP triggers.

This enhancement improves the robustness of the driver when operating in
environments where electrical anomalies may occur, particularly with SD
and MS card interfaces.

Signed-off-by: Ricky Wu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/memstick/host/rtsx_usb_ms.c

···
 
 	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_CLK_EN, MS_CLK_EN, 0);
 	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_OE, MS_OUTPUT_EN, 0);
-
+	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_PWR_CTL,
+			POWER_MASK, POWER_OFF);
+	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_PWR_CTL,
+			POWER_MASK | LDO3318_PWR_MASK, POWER_OFF | LDO_SUSPEND);
 	err = rtsx_usb_send_cmd(ucr, MODE_C, 100);
 	if (err < 0)
 		return err;

drivers/misc/cardreader/rtsx_usb.c

···
 	ret = rtsx_usb_send_cmd(ucr, MODE_C, 100);
 	if (ret)
 		return ret;
+	/* config OCP */
+	rtsx_usb_write_register(ucr, OCPCTL, MS_OCP_DETECT_EN, MS_OCP_DETECT_EN);
+	rtsx_usb_write_register(ucr, OCPPARA1, 0xF0, 0x50);
+	rtsx_usb_write_register(ucr, OCPPARA2, 0x7, 0x3);
 
 	/* config non-crystal mode */
 	rtsx_usb_read_register(ucr, CFG_MODE, &val);
···
 			if (val & (SD_CD | MS_CD)) {
 				device_for_each_child(&intf->dev, NULL, rtsx_usb_resume_child);
 				return -EAGAIN;
+			} else {
+				/* if the card does not exists, clear OCP status */
+				rtsx_usb_write_register(ucr, OCPCTL, MS_OCP_CLEAR, MS_OCP_CLEAR);
 			}
 		} else {
 			/* There is an ongoing operation*/

drivers/mmc/host/rtsx_usb_sdmmc.c

···
 	bool			ddr_mode;
 
 	unsigned char		power_mode;
-
+	u16			ocp_stat;
 #ifdef RTSX_USB_USE_LEDS_CLASS
 	struct led_classdev	led;
 	char			led_name[32];
···
 
 	mutex_unlock(&ucr->dev_mutex);
 
+	/* get OCP status */
+	host->ocp_stat = (val >> 4) & 0x03;
+
 	/* Treat failed detection as non-exist */
 	if (err)
 		goto no_card;
···
 	}
 
 no_card:
+	/* clear OCP status */
+	if (host->ocp_stat & (MS_OCP_NOW | MS_OCP_EVER)) {
+		rtsx_usb_write_register(ucr, OCPCTL, MS_OCP_CLEAR, MS_OCP_CLEAR);
+		host->ocp_stat = 0;
+	}
 	host->card_exist = false;
 	return 0;
 }
···
 		cmd->error = -ENOMEDIUM;
 		goto finish_detect_card;
 	}
-
+	/* check OCP stat */
+	if (host->ocp_stat & (MS_OCP_NOW | MS_OCP_EVER)) {
+		cmd->error = -ENOMEDIUM;
+		goto finish_detect_card;
+	}
 	mutex_lock(&ucr->dev_mutex);
 
 	mutex_lock(&host->host_mutex);
···
 	struct rtsx_ucr *ucr = host->ucr;
 	int err;
 
+	if (host->ocp_stat & (MS_OCP_NOW | MS_OCP_EVER)) {
+		dev_dbg(sdmmc_dev(host), "over current\n");
+		return -EIO;
+	}
 	dev_dbg(sdmmc_dev(host), "%s\n", __func__);
 	rtsx_usb_init_cmd(ucr);
 	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_SELECT, 0x07, SD_MOD_SEL);
···
 	usleep_range(800, 1000);
 
 	rtsx_usb_init_cmd(ucr);
+	/* WA OCP issue: after OCP, there were problems with reopen card power */
+	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_PWR_CTL, POWER_MASK, POWER_ON);
+	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, FPDCTL, SSC_POWER_MASK, SSC_POWER_DOWN);
+	err = rtsx_usb_send_cmd(ucr, MODE_C, 100);
+	if (err)
+		return err;
+	msleep(20);
+	rtsx_usb_write_register(ucr, FPDCTL, SSC_POWER_MASK, SSC_POWER_ON);
+	usleep_range(180, 200);
+	rtsx_usb_init_cmd(ucr);
 	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_PWR_CTL,
-			POWER_MASK|LDO3318_PWR_MASK, POWER_ON|LDO_ON);
+			LDO3318_PWR_MASK, LDO_ON);
 	rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_OE,
 			SD_OUTPUT_EN, SD_OUTPUT_EN);
 
···
 	mmc->max_req_size = 524288;
 
 	host->power_mode = MMC_POWER_OFF;
+	host->ocp_stat = 0;
 }
 
 static int rtsx_usb_sdmmc_drv_probe(struct platform_device *pdev)

include/linux/rtsx_usb.h

···
 #define CD_MASK		(SD_CD | MS_CD | XD_CD)
 #define SD_WP		0x08
 
+/* OCPCTL */
+#define MS_OCP_DETECT_EN		0x08
+#define	MS_OCP_INT_EN			0x04
+#define	MS_OCP_INT_CLR			0x02
+#define	MS_OCP_CLEAR			0x01
+
+/* OCPSTAT */
+#define MS_OCP_DETECT			0x80
+#define MS_OCP_NOW			0x02
+#define MS_OCP_EVER			0x01
+
 /* reader command field offset & parameters */
 #define READ_REG_CMD		0
 #define WRITE_REG_CMD		1