[PATCH] mmc: renesas-sdhi: Disable clock after tuning reset when possible

[Marek Vasut]

Currently the renesas_sdhi_reset_tuning() unconditionally leaves SDHI
clock enabled after the tuning reset. This is not always necessary.

After the driver performed tuning reset at the end of probe function,
or in the unlikely case that tuning failed during regular operation,
the SDHI clock can be disabled after the tuning reset. The following
set_ios call would reconfigure the clock as needed.

In case of regular set_ios call which requires a tuning reset, keep
the clock enabled or disabled according to the mmc->clk_disable state.

With this in place, the controllers which have not been accessed via
block subsystem after boot are left in quiescent state. However, if an
MMC device is used e.g. for environment storage, that controller would
be accessed during the environment load and left active, including its
clock which would still be generated. This is due to the design of the
MMC subsystem, which does not deinit a controller after it was started
once, the controller is only deinited in case of mmc rescan, or before
OS boot.

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Note: To address the part where MMC device has been inited once and
      is never deinited until rescan or OS boot, it would likely be
      necessary to implement something like runtime PM, possibly
      based on the cyclic framework. Basically, keep track of when
      the MMC was accessed last, and if certain time elapsed, deinit
      the MMC. This could also be used to handle card detect polling
      at the same time.
---
Cc: Jaehoon Chung <jh80.chung at samsung.com>
Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
Cc: Paul Barker <paul.barker.ct at bp.renesas.com>
Cc: Peng Fan <peng.fan at nxp.com>
---
 drivers/mmc/renesas-sdhi.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/renesas-sdhi.c b/drivers/mmc/renesas-sdhi.c
index 8cd501c5f7c..97aaf1e4ec3 100644
--- a/drivers/mmc/renesas-sdhi.c
+++ b/drivers/mmc/renesas-sdhi.c
@@ -318,7 +318,7 @@ static unsigned int renesas_sdhi_init_tuning(struct tmio_sd_priv *priv)
 		RENESAS_SDHI_SCC_DTCNTL_TAPNUM_MASK;
 }
 
-static void renesas_sdhi_reset_tuning(struct tmio_sd_priv *priv)
+static void renesas_sdhi_reset_tuning(struct tmio_sd_priv *priv, bool clk_disable)
 {
 	u32 reg;
 
@@ -350,6 +350,12 @@ static void renesas_sdhi_reset_tuning(struct tmio_sd_priv *priv)
 	reg = tmio_sd_readl(priv, RENESAS_SDHI_SCC_RVSCNTL);
 	reg &= ~RENESAS_SDHI_SCC_RVSCNTL_RVSEN;
 	tmio_sd_writel(priv, reg, RENESAS_SDHI_SCC_RVSCNTL);
+
+	if (clk_disable) {
+		reg = tmio_sd_readl(priv, TMIO_SD_CLKCTL);
+		reg &= ~TMIO_SD_CLKCTL_SCLKEN;
+		tmio_sd_writel(priv, reg, TMIO_SD_CLKCTL);
+	}
 }
 
 static int renesas_sdhi_hs400(struct udevice *dev)
@@ -629,7 +635,7 @@ int renesas_sdhi_execute_tuning(struct udevice *dev, uint opcode)
 out:
 	if (ret < 0) {
 		dev_warn(dev, "Tuning procedure failed\n");
-		renesas_sdhi_reset_tuning(priv);
+		renesas_sdhi_reset_tuning(priv, true);
 	}
 
 	return ret;
@@ -668,7 +674,7 @@ static int renesas_sdhi_set_ios(struct udevice *dev)
 	    (mmc->selected_mode != UHS_SDR104) &&
 	    (mmc->selected_mode != MMC_HS_200) &&
 	    (mmc->selected_mode != MMC_HS_400)) {
-		renesas_sdhi_reset_tuning(priv);
+		renesas_sdhi_reset_tuning(priv, mmc->clk_disable);
 	}
 #endif
 
@@ -1095,7 +1101,7 @@ static int renesas_sdhi_probe(struct udevice *dev)
     CONFIG_IS_ENABLED(MMC_HS200_SUPPORT) || \
     CONFIG_IS_ENABLED(MMC_HS400_SUPPORT)
 	if (priv->caps & TMIO_SD_CAP_RCAR_UHS)
-		renesas_sdhi_reset_tuning(priv);
+		renesas_sdhi_reset_tuning(priv, true);
 #endif
 	return 0;
 
-- 
2.42.0