clk: at91: main: warn when the main crystal frequency is not set

When the main crystal frequency is not set, the main clock is approximated using
the MAINF value in the CKGR_MCFR register. Warn the user in that case.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Boris BREZILLON <boris.brezillon@overkiz.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/at91/clk-main.c

@@ -388,6 +388,7 @@ static unsigned long clk_main_recalc_rate(struct at91_pmc *pmc,
 	if (parent_rate)
 		return parent_rate;
 
+	pr_warn("Main crystal frequency not set, using approximate value\n");
 	tmp = pmc_read(pmc, AT91_CKGR_MCFR);
 	if (!(tmp & AT91_PMC_MAINRDY))
 		return 0;