[PATCH V8 16/23] mmc: sdhci-uhs2: add clock operations

[Victor Shih]

From: Victor Shih <victor.shih@xxxxxxxxxxxxxxxxxxx>

This is a sdhci version of mmc's uhs2_[enable|disable]_clk operations.

Updates in V8:
 - Remove unnecessary include file.
 - read_poll_timeout() to instead of read_poll_timeout_atomic()
   in sdhci_uhs2_enable_clk().
 - Put the comment on the end and put the lines in descending
   line length in sdhci_uhs2_enable_clk().
 - Modify return value in sdhci_uhs2_enable_clk().

Updates in V6:
 - Remove unnecessary functions.

Signed-off-by: Ben Chuang <ben.chuang@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Signed-off-by: Victor Shih <victor.shih@xxxxxxxxxxxxxxxxxxx>
---
 drivers/mmc/host/sdhci-uhs2.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
index 4c2a56629ab3..af1b0c5e48fd 100644
--- a/drivers/mmc/host/sdhci-uhs2.c
+++ b/drivers/mmc/host/sdhci-uhs2.c
@@ -329,6 +329,36 @@ static int sdhci_uhs2_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	return 0;
 }
 
+static int sdhci_uhs2_disable_clk(struct mmc_host *mmc)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+
+	clk &= ~SDHCI_CLOCK_CARD_EN;
+	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+
+	return 0;
+}
+
+static int sdhci_uhs2_enable_clk(struct mmc_host *mmc)
+{
+	struct sdhci_host *host = mmc_priv(mmc);
+	u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	int timeout_us = 20000; /* 20ms */
+	u32 val;
+
+	clk |= SDHCI_CLOCK_CARD_EN;
+	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+
+	if (read_poll_timeout(sdhci_readw, val, (val & SDHCI_CLOCK_INT_STABLE),
+			      10, timeout_us, true, host, SDHCI_CLOCK_CONTROL)) {
+		pr_err("%s: Internal clock never stabilised.\n", mmc_hostname(host->mmc));
+		sdhci_dumpregs(host);
+		return -EIO;
+	}
+	return 0;
+}
+
 /*****************************************************************************\
  *                                                                           *
  * Driver init/exit                                                          *
-- 
2.25.1