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powerpc/5200: add function to return external clock frequency

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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>
This commit is contained in:
Wolfgang Grandegger 2009-03-11 09:36:26 -06:00 committed by Grant Likely
parent bb899d49a5
commit df8a95f46f
2 changed files with 38 additions and 0 deletions
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1
arch/powerpc/include/asm/mpc52xx.h
View File

@ -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 */

37
arch/powerpc/platforms/52xx/mpc52xx_common.c
View File

@ -205,6 +205,43 @@ int mpc52xx_set_psc_clkdiv(int psc_id, int clkdiv)
}
EXPORT_SYMBOL(mpc52xx_set_psc_clkdiv);
/**
* mpc52xx_get_xtal_freq - Get SYS_XTAL_IN frequency for a device
*
* @node: device node
*
* Returns the frequency of the external oscillator clock connected
* to the SYS_XTAL_IN pin, or 0 if it cannot be determined.
*/
unsigned int mpc52xx_get_xtal_freq(struct device_node *node)
{
u32 val;
unsigned int freq;
if (!mpc52xx_cdm)
return 0;
freq = mpc52xx_find_ipb_freq(node);
if (!freq)
return 0;
if (in_8(&mpc52xx_cdm->ipb_clk_sel) & 0x1)
freq *= 2;
val = in_be32(&mpc52xx_cdm->rstcfg);
if (val & (1 << 5))
freq *= 8;
else
freq *= 4;
if (val & (1 << 6))
freq /= 12;
else
freq /= 16;
return freq;
}
EXPORT_SYMBOL(mpc52xx_get_xtal_freq);
/**
* mpc52xx_restart: ppc_md->restart hook for mpc5200 using the watchdog timer
*/