+	ret = clk_prepare_enable(i2c->clk);
+	if (ret)
+		dev_err(&pdev->dev, "Unable to enable clock.\n");

Don't you want to bail out here? The clk refcounting will be messed up
if you continue.

+err_clk_dis:
+	clk_disable_unprepare(i2c->clk);
+	pm_runtime_set_suspended(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+	return ret;

To match the inverse of the activation order, I'd put the
clk_disable_unprepare after the pm_* calls. Couldn't it happen that
those calls need to change the clk state?