linux-kernel - [PATCH v4] mmc: rtsx: usb add 74 clocks in poweron flow

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Message-ID: <20250616064956.1846258-1-ricky_wu@realtek.com>
Date: Mon, 16 Jun 2025 14:49:56 +0800
From: Ricky Wu <ricky_wu@...ltek.com>
To: <linux-kernel@...r.kernel.org>, <ulf.hansson@...aro.org>,
        <linux-mmc@...r.kernel.org>, <viro@...iv.linux.org.uk>,
        <ricky_wu@...ltek.com>
Subject: [PATCH v4] mmc: rtsx: usb add 74 clocks in poweron flow

SD spec definition:
"Host provides at least 74 Clocks before issuing first command"

add issue the clocks when power_mode is POWER_UP
and stop the signal when power_mode is POWER_ON

Signed-off-by: Ricky Wu <ricky_wu@...ltek.com>
---
v2: remove delay 100ms in power_on
v3: Use switch-case instead of if statements
v4: re-base on the patches
https://lore.kernel.org/all/20250610111633.504366-1-ulf.hansson@linaro.org/
---
 drivers/mmc/host/rtsx_usb_sdmmc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
index c1fdcc334c8f..239eb9acf7a7 100644
--- a/drivers/mmc/host/rtsx_usb_sdmmc.c
+++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
@@ -1014,6 +1014,7 @@ static void sd_set_power_mode(struct rtsx_usb_sdmmc *host,
 		unsigned char power_mode)
 {
 	int err;
+	struct rtsx_ucr *ucr = host->ucr;
 
 	if (power_mode == host->power_mode)
 		return;
@@ -1031,9 +1032,13 @@ static void sd_set_power_mode(struct rtsx_usb_sdmmc *host,
 		err = sd_power_on(host);
 		if (err)
 			dev_dbg(sdmmc_dev(host), "power-on (err = %d)\n", err);
+		/* issue the clock signals to card at least 74 clocks */
+		rtsx_usb_write_register(ucr, SD_BUS_STAT, SD_CLK_TOGGLE_EN, SD_CLK_TOGGLE_EN);
 		break;
 
 	case MMC_POWER_ON:
+		/* stop to send the clock signals */
+		rtsx_usb_write_register(ucr, SD_BUS_STAT, SD_CLK_TOGGLE_EN, 0x00);
 	case MMC_POWER_UNDEFINED:
 		break;
 
-- 
2.25.1