[PATCH v2] mmc: sdhci-of-at91: disable selectively clocks on pm runtime

[Aubin Constans <aubin.constans@microchip.com>]

From: Claudiu Beznea <claudiu.beznea@microchip.com>

SDMMC run-time clock disabling is not supported in newer SoCs, including
SAMA7G54, SAMA7D65 and LAN969x.

Make the clock disabling scenario conditional:
- still enabled for the sama5d2 and sam9x60 compatibles (which are all
  those implemented at present),
- otherwise avoided by default, for subsequent SoC families.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
[Romain: Fix unbalanced clock activation/deactivation]
Co-developed-by: Romain Sioen <romain.sioen@microchip.com>
Signed-off-by: Romain Sioen <romain.sioen@microchip.com>
[Aubin: Rebase before sama7g5 support and edit the commit msg]
Signed-off-by: Aubin Constans <aubin.constans@microchip.com>
Tested-by: Robert Marko <robert.marko@sartura.hr>
---
Changes in v2:
- Edit the commit msg to say the patch prepares SAMA7G54/SAMA7D65/LAN969x
  SoC support w/o immediate change.
  Also, move and summarize Romain's own commit msg close to its sign-off.
- Restore Claudiu's author and sign-off email to the microchip.com address
  he had upon writing the patch.
- Link to v1: https://lore.kernel.org/r/20260918153414.909333-1-aubin.constans@microchip.com

 drivers/mmc/host/sdhci-of-at91.c | 36 ++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
index 7c4ac65f247d..399856643e57 100644
--- a/drivers/mmc/host/sdhci-of-at91.c
+++ b/drivers/mmc/host/sdhci-of-at91.c
@@ -39,6 +39,7 @@ struct sdhci_at91_soc_data {
 	const struct sdhci_pltfm_data *pdata;
 	bool baseclk_is_generated_internally;
 	unsigned int divider_for_baseclk;
+	bool pm_runtime_disable_clks;
 };
 
 struct sdhci_at91_priv {
@@ -149,12 +150,14 @@ static const struct sdhci_pltfm_data sdhci_sama5d2_pdata = {
 static const struct sdhci_at91_soc_data soc_data_sama5d2 = {
 	.pdata = &sdhci_sama5d2_pdata,
 	.baseclk_is_generated_internally = false,
+	.pm_runtime_disable_clks = true,
 };
 
 static const struct sdhci_at91_soc_data soc_data_sam9x60 = {
 	.pdata = &sdhci_sama5d2_pdata,
 	.baseclk_is_generated_internally = true,
 	.divider_for_baseclk = 2,
+	.pm_runtime_disable_clks = true,
 };
 
 static const struct of_device_id sdhci_at91_dt_match[] = {
@@ -164,7 +167,7 @@ static const struct of_device_id sdhci_at91_dt_match[] = {
 };
 MODULE_DEVICE_TABLE(of, sdhci_at91_dt_match);
 
-static int sdhci_at91_set_clks_presets(struct device *dev)
+static int sdhci_at91_set_clks_presets(struct device *dev, bool start_clks)
 {
 	struct sdhci_host *host = dev_get_drvdata(dev);
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -174,7 +177,14 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
 	unsigned int			gck_rate, clk_base_rate;
 	unsigned int			preset_div;
 
-	clk_prepare_enable(priv->hclock);
+	/*
+	 * Manage clock prepare/enable procedure depending on if the board
+	 * support runtime clock disabling and if we come from the probing
+	 * or restoring procedure (for backup+self refresh).
+	 */
+	if (start_clks)
+		clk_prepare_enable(priv->hclock);
+
 	caps0 = readl(host->ioaddr + SDHCI_CAPABILITIES);
 	caps1 = readl(host->ioaddr + SDHCI_CAPABILITIES_1);
 
@@ -223,8 +233,11 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
 	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
 	       host->ioaddr + SDHCI_PRESET_FOR_DDR50);
 
-	clk_prepare_enable(priv->mainck);
-	clk_prepare_enable(priv->gck);
+	/* Same clock management as for hclock */
+	if (start_clks) {
+		clk_prepare_enable(priv->mainck);
+		clk_prepare_enable(priv->gck);
+	}
 
 	return 0;
 }
@@ -254,9 +267,11 @@ static int sdhci_at91_runtime_suspend(struct device *dev)
 	if (host->tuning_mode != SDHCI_TUNING_MODE_3)
 		mmc_retune_needed(host->mmc);
 
-	clk_disable_unprepare(priv->gck);
-	clk_disable_unprepare(priv->hclock);
-	clk_disable_unprepare(priv->mainck);
+	if (priv->soc_data->pm_runtime_disable_clks) {
+		clk_disable_unprepare(priv->gck);
+		clk_disable_unprepare(priv->hclock);
+		clk_disable_unprepare(priv->mainck);
+	}
 
 	return 0;
 }
@@ -269,7 +284,7 @@ static int sdhci_at91_runtime_resume(struct device *dev)
 	int ret;
 
 	if (priv->restore_needed) {
-		ret = sdhci_at91_set_clks_presets(dev);
+		ret = sdhci_at91_set_clks_presets(dev, priv->soc_data->pm_runtime_disable_clks);
 		if (ret)
 			return ret;
 
@@ -277,6 +292,9 @@ static int sdhci_at91_runtime_resume(struct device *dev)
 		goto out;
 	}
 
+	if (!priv->soc_data->pm_runtime_disable_clks)
+		goto out;
+
 	ret = clk_prepare_enable(priv->mainck);
 	if (ret) {
 		dev_err(dev, "can't enable mainck\n");
@@ -344,7 +362,7 @@ static int sdhci_at91_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(priv->gck),
 				     "failed to get multclk\n");
 
-	ret = sdhci_at91_set_clks_presets(&pdev->dev);
+	ret = sdhci_at91_set_clks_presets(&pdev->dev, true);
 	if (ret)
 		return ret;
 
-- 
2.43.0