clk: x86: Do not gate clocks enabled by the firmware

Read the enable register to determine if the clock is already in use by
the firmware. In this case avoid gating the clock.
Tested-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: NDarren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: NCarlo Caione <carlo@endlessm.com>
Fixes: 282a4e4c ("platform/x86: Enable Atom PMC platform clocks")
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>

drivers/clk/x86/clk-pmc-atom.c

@@ -186,6 +186,13 @@ static struct clk_plt *plt_clk_register(struct platform_device *pdev, int id,
 	pclk->reg = base + PMC_CLK_CTL_OFFSET + id * PMC_CLK_CTL_SIZE;
 	spin_lock_init(&pclk->lock);
 
+	/*
+	 * If the clock was already enabled by the firmware mark it as critical
+	 * to avoid it being gated by the clock framework if no driver owns it.
+	 */
+	if (plt_clk_is_enabled(&pclk->hw))
+		init.flags |= CLK_IS_CRITICAL;
+
 	ret = devm_clk_hw_register(&pdev->dev, &pclk->hw);
 	if (ret) {
 		pclk = ERR_PTR(ret);