powerpc/5200: add function to return external clock frequency

This patch adds the utility function mpc52xx_get_xtal_freq() to get
the frequency of the external oscillator clock connected to the pin
SYS_XTAL_IN. The MSCAN may us it as clock source. Unfortunately, this
value is not available from the FDT blob, but it can be determined
from the IPB frequency.

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/mpc52xx.h b/arch/powerpc/include/asm/mpc52xx.h
index 81a23932a160..52e049cd9e68 100644
--- a/arch/powerpc/include/asm/mpc52xx.h
+++ b/arch/powerpc/include/asm/mpc52xx.h
@@ -273,6 +273,7 @@ extern void mpc5200_setup_xlb_arbiter(void);
 extern void mpc52xx_declare_of_platform_devices(void);
 extern void mpc52xx_map_common_devices(void);
 extern int mpc52xx_set_psc_clkdiv(int psc_id, int clkdiv);
+extern unsigned int mpc52xx_get_xtal_freq(struct device_node *node);
 extern void mpc52xx_restart(char *cmd);
 
 /* mpc52xx_pic.c */