[PATCH v1 6/7] mci: imx-esdhc: make the transfer mode selectable (PIO/SDMA/ADMA2)

[Johannes Schneider <johannes.schneider@leica-geosystems.com>]

The driver only offered a PIO-or-DMA toggle (CONFIG_MCI_IMX_ESDHC_PIO) and
never called sdhci_setup_adma(), so the controller-resident ADMA2 engine was
unreachable and DMA always meant SDMA.

Replace the single bool with a choice of PIO/SDMA/ADMA2, defaulting to SDMA so
existing configs keep their current behaviour, and call sdhci_setup_adma() in
probe under the ADMA2 option (mirroring the Rockchip dwcmshc driver). It
returns -ENOTSUPP and cleanly falls back to SDMA on controllers without ADMA2
capability, so the new option is safe on all i.MX/Layerscape variants.

Assisted-by: Claude Opus 4.8 (1M context)
Signed-off-by: Johannes Schneider <johannes.schneider@leica-geosystems.com>
---
 drivers/mci/Kconfig     | 19 ++++++++++++++++---
 drivers/mci/imx-esdhc.c |  7 +++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/mci/Kconfig b/drivers/mci/Kconfig
index b38f7a3bdf..cd8862722c 100644
--- a/drivers/mci/Kconfig
+++ b/drivers/mci/Kconfig
@@ -169,11 +169,24 @@ config MCI_IMX_ESDHC
 	  Enable this entry to add support to read and write SD cards on a
 	  Freescale i.MX25/35/51 based system.
 
-config MCI_IMX_ESDHC_PIO
-	bool "use PIO mode"
+choice
+	prompt "i.MX esdhc transfer mode"
+	default MCI_IMX_ESDHC_SDMA
 	depends on MCI_IMX_ESDHC
 	help
-	  mostly useful for debugging. Normally you should use DMA.
+	  How the driver moves data words to/from the controller. SDMA and
+	  ADMA2 use the controller's DMA engine; PIO is CPU-driven and slow.
+
+config MCI_IMX_ESDHC_PIO
+	bool "PIO"
+
+config MCI_IMX_ESDHC_SDMA
+	bool "SDMA"
+
+config MCI_IMX_ESDHC_ADMA2
+	bool "ADMA2"
+
+endchoice
 
 config MCI_OMAP_HSMMC
 	bool "OMAP HSMMC"
diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
index e123bd3ede..3536ebd6b8 100644
--- a/drivers/mci/imx-esdhc.c
+++ b/drivers/mci/imx-esdhc.c
@@ -698,6 +698,13 @@ static int fsl_esdhc_probe(struct device *dev)
 	if (ret)
 		goto err_clk_disable;
 
+	if (IS_ENABLED(CONFIG_MCI_IMX_ESDHC_ADMA2)) {
+		ret = sdhci_setup_adma(&host->sdhci);
+		if (ret && ret != -ENOTSUPP)
+			dev_warn(dev, "ADMA setup failed (%pe), falling back to SDMA\n",
+				 ERR_PTR(ret));
+	}
+
 	if (esdhc_is_usdhc(host) || esdhc_is_layerscape(host))
 		mci->host_caps |= MMC_CAP_3_3V_DDR | MMC_CAP_1_8V_DDR;
 
-- 
2.43.0