linux-kernel - [RFC PATCH v3.1 14/27] mmc: sdhci-uhs2: skip signal_voltage

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Message-Id: <20201106022726.19831-15-takahiro.akashi@linaro.org>
Date:   Fri,  6 Nov 2020 11:27:13 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     ulf.hansson@...aro.org, adrian.hunter@...el.com
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ben.chuang@...esyslogic.com.tw, greg.tu@...esyslogic.com.tw,
        AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: [RFC PATCH v3.1 14/27] mmc: sdhci-uhs2: skip signal_voltage_switch()

For UHS2, the signal voltage is supplied by vdd2 which is already 1.8v,
so no voltage switch required.

Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
---
 drivers/mmc/host/sdhci-uhs2.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
index 2bf78cc4e9ed..1eca89359351 100644
--- a/drivers/mmc/host/sdhci-uhs2.c
+++ b/drivers/mmc/host/sdhci-uhs2.c
@@ -178,6 +178,29 @@ void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode,
 }
 EXPORT_SYMBOL_GPL(sdhci_uhs2_set_power);
 
+/*****************************************************************************\
+ *                                                                           *
+ * MMC callbacks                                                             *
+ *                                                                           *
+\*****************************************************************************/
+
+static int sdhci_uhs2_start_signal_voltage_switch(struct mmc_host *mmc,
+						  struct mmc_ios *ios)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+
+	/*
+	 * For UHS2, the signal voltage is supplied by vdd2 which is
+	 * already 1.8v so no voltage switch required.
+	 */
+        if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
+             host->version >= SDHCI_SPEC_400 &&
+             host->mmc->flags & MMC_UHS2_SUPPORT)
+                return 0;
+
+	return sdhci_start_signal_voltage_switch(mmc, ios);
+}
+
 /*****************************************************************************\
  *                                                                           *
  * Driver init/exit                                                          *
@@ -186,6 +209,9 @@ EXPORT_SYMBOL_GPL(sdhci_uhs2_set_power);
 
 static int sdhci_uhs2_host_ops_init(struct sdhci_host *host)
 {
+	host->mmc_host_ops.start_signal_voltage_switch =
+		sdhci_uhs2_start_signal_voltage_switch;
+
 	return 0;
 }
 
-- 
2.28.0