[PATCH v2 2/4] mmc: meson-gx: enable the bus pipeline clock on T7

[Lucas Tanure <tanure@linux.com>]

On the T7 SoC, the bus path between the SD/eMMC controllers and the
NIC_MATRIX fabric goes through a pipeline stage inserted by the hardware
design to help timing closure. The stage has its own gate clock and,
when that clock is disabled, a controller that starts a DMA transfer can
never complete it, hanging the storage devices and, from there, the
whole system.

Add a dedicated match data for the amlogic,t7-mmc compatible that makes
the driver claim and enable the "pipeline" clock for as long as the
device is bound.

The clock is deliberately not optional: the hardware cannot do DMA
without it, and failing the probe with a clear error is preferable to
booting and hitting an undiagnosable DMA hang later.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Lucas Tanure <tanure@linux.com>
---
 drivers/mmc/host/meson-gx-mmc.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 694bb443d5f3..c0f1e929fc13 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -139,6 +139,7 @@ struct meson_mmc_data {
 	unsigned int always_on;
 	unsigned int adjust;
 	unsigned int irq_sdio_sleep;
+	bool has_pipeline_clk;
 };
 
 struct sd_emmc_desc {
@@ -1204,6 +1205,15 @@ static int meson_mmc_probe(struct platform_device *pdev)
 	if (IS_ERR(core_clk))
 		return PTR_ERR(core_clk);
 
+	if (host->data->has_pipeline_clk) {
+		struct clk *pipe_clk;
+
+		pipe_clk = devm_clk_get_enabled(&pdev->dev, "pipeline");
+		if (IS_ERR(pipe_clk))
+			return dev_err_probe(&pdev->dev, PTR_ERR(pipe_clk),
+					     "missing pipeline clock\n");
+	}
+
 	ret = meson_mmc_clk_init(host);
 	if (ret)
 		return ret;
@@ -1322,12 +1332,22 @@ static const struct meson_mmc_data meson_axg_data = {
 	.irq_sdio_sleep	= CLK_V3_IRQ_SDIO_SLEEP,
 };
 
+static const struct meson_mmc_data meson_t7_data = {
+	.tx_delay_mask	= CLK_V3_TX_DELAY_MASK,
+	.rx_delay_mask	= CLK_V3_RX_DELAY_MASK,
+	.always_on	= CLK_V3_ALWAYS_ON,
+	.adjust		= SD_EMMC_V3_ADJUST,
+	.irq_sdio_sleep	= CLK_V3_IRQ_SDIO_SLEEP,
+	.has_pipeline_clk = true,
+};
+
 static const struct of_device_id meson_mmc_of_match[] = {
 	{ .compatible = "amlogic,meson-gx-mmc",		.data = &meson_gx_data },
 	{ .compatible = "amlogic,meson-gxbb-mmc", 	.data = &meson_gx_data },
 	{ .compatible = "amlogic,meson-gxl-mmc",	.data = &meson_gx_data },
 	{ .compatible = "amlogic,meson-gxm-mmc",	.data = &meson_gx_data },
 	{ .compatible = "amlogic,meson-axg-mmc",	.data = &meson_axg_data },
+	{ .compatible = "amlogic,t7-mmc",		.data = &meson_t7_data },
 	{}
 };
 MODULE_DEVICE_TABLE(of, meson_mmc_of_match);
-- 
2.55.0