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drm/omap: add comments for PLL calculations 

Add comments showing how the PLL clock rates are calculated.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
This commit is contained in:
Tomi Valkeinen 2016-05-18 12:04:47 +03:00
parent c107751d12
commit f44b717c3d
1 changed files with 7 additions and 0 deletions
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7
drivers/gpu/drm/omapdrm/dss/pll.c
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@ -207,6 +207,10 @@ bool dss_pll_hsdiv_calc_a(const struct dss_pll *pll, unsigned long clkdco,
return false; return false;
} }
/*
* clkdco = clkin / n * m * 2
* clkoutX = clkdco / mX
*/
bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin, bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin,
unsigned long pll_min, unsigned long pll_max, unsigned long pll_min, unsigned long pll_max,
dss_pll_calc_func func, void *data) dss_pll_calc_func func, void *data)
@ -252,6 +256,9 @@ bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin,
* This calculates a PLL config that will provide the target_clkout rate * This calculates a PLL config that will provide the target_clkout rate
* for clkout. Additionally clkdco rate will be the same as clkout rate * for clkout. Additionally clkdco rate will be the same as clkout rate
* when clkout rate is >= min_clkdco. * when clkout rate is >= min_clkdco.
*
* clkdco = clkin / n * m + clkin / n * mf / 262144
* clkout = clkdco / m2
*/ */
bool dss_pll_calc_b(const struct dss_pll *pll, unsigned long clkin, bool dss_pll_calc_b(const struct dss_pll *pll, unsigned long clkin,
unsigned long target_clkout, struct dss_pll_clock_info *cinfo) unsigned long target_clkout, struct dss_pll_clock_info *cinfo)