Hi,
I'm trying to enable MMC/SD access on a VoCore2 SOM (based on MT7628)
using mtk_sd driver.

Just enabling mtk_sd will bomb wit undefined function `clk_get_parent`;
this can be trivially cured with:

diff --git a/arch/mips/ralink/clk.c b/arch/mips/ralink/clk.c
index 2f9d5acb38ea..930c2776f6fd 100644
--- a/arch/mips/ralink/clk.c
+++ b/arch/mips/ralink/clk.c

@@ -85,3 +85,9 @@ void __init plat_time_init(void)

        clk_put(clk);
        timer_probe();
 }
+
+struct clk *clk_get_parent(struct clk *clk)
+{
+       return NULL;
+}
+EXPORT_SYMBOL_GPL(clk_get_parent);


Naive implementation fails runtime with ENOENT in
devm_clk_get("10130000.mmc", "source") in spite of clock definition in .dts.

I traced the problem to CONFIG_COMMON_CLK not being defined for RALINK.
It cannot be enabled because it will lead to multiple definition of
several clock-related functions (e.g.: `clk_get_rate`).
I found completely disabling clock handling in mtk_sd.c leads to a (for
me) fully working SD card.

diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
index 7726dcf48f2c..464f64bea7c6 100644
--- a/drivers/mmc/host/mtk-sd.c
+++ b/drivers/mmc/host/mtk-sd.c

@@ -730,18 +730,22 @@ static void msdc_set_timeout(struct msdc_host

*host, u32 ns, u32 clks)
 
 static void msdc_gate_clock(struct msdc_host *host)
 {
+#ifdef CONFIG_COMMON_CLK
     clk_disable_unprepare(host->src_clk_cg);
     clk_disable_unprepare(host->src_clk);
     clk_disable_unprepare(host->bus_clk);
     clk_disable_unprepare(host->h_clk);
+#endif
 }
 
 static void msdc_ungate_clock(struct msdc_host *host)
 {
+#ifdef CONFIG_COMMON_CLK
     clk_prepare_enable(host->h_clk);
     clk_prepare_enable(host->bus_clk);
     clk_prepare_enable(host->src_clk);
     clk_prepare_enable(host->src_clk_cg);
+#endif
     while (!(readl(host->base + MSDC_CFG) & MSDC_CFG_CKSTB))
         cpu_relax();
 }

@@ -2211,6 +2215,7 @@ static int msdc_drv_probe(struct platform_device

*pdev)
     if (ret)
         goto host_free;
 
+#ifdef CONFIG_COMMON_CLK
     host->src_clk = devm_clk_get(&pdev->dev, "source");
     if (IS_ERR(host->src_clk)) {
         ret = PTR_ERR(host->src_clk);

@@ -2230,6 +2235,12 @@ static int msdc_drv_probe(struct platform_device

*pdev)
     host->src_clk_cg = devm_clk_get(&pdev->dev, "source_cg");
     if (IS_ERR(host->src_clk_cg))
         host->src_clk_cg = NULL;
+#else
+    host->src_clk = NULL;
+    host->h_clk = NULL;
+    host->bus_clk = NULL;
+    host->src_clk_cg = NULL;
+#endif
 
     host->irq = platform_get_irq(pdev, 0);
     if (host->irq < 0) {


... but I'm unsure this hack-and-slash approach is the Right Thing to do ;)