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clk: clk_stm32f: Add set_rate for LTDC clock

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Implement set_rate() for LTDC clock only, set_rate for other
clocks will be added if needed. This is needed by future LTDC driver
improvements.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
This commit is contained in:
Patrice Chotard 2018-02-08 17:20:50 +01:00 committed by Tom Rini
parent e8fb9ed254
commit 5e993508cb
1 changed files with 100 additions and 0 deletions
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100
drivers/clk/clk_stm32f.c
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@ -136,6 +136,9 @@ struct stm32_clk {
unsigned long hse_rate;
};
#ifdef CONFIG_VIDEO_STM32
static const u8 plldivr_table[] = { 0, 0, 2, 3, 4, 5, 6, 7 };
#endif
static const u8 pllsaidivr_table[] = { 2, 4, 8, 16 };
static int configure_clocks(struct udevice *dev)
@ -484,7 +487,104 @@ static ulong stm32_clk_get_rate(struct clk *clk)
static ulong stm32_set_rate(struct clk *clk, ulong rate)
{
#ifdef CONFIG_VIDEO_STM32
struct stm32_clk *priv = dev_get_priv(clk->dev);
struct stm32_rcc_regs *regs = priv->base;
u32 pllsair_rate, pllsai_vco_rate, current_rate;
u32 best_div, best_diff, diff;
u16 div;
u8 best_plldivr, best_pllsaidivr;
u8 i, j;
bool found = false;
/* Only set_rate for LTDC clock is implemented */
if (clk->id != STM32F7_APB2_CLOCK(LTDC)) {
pr_err("set_rate not implemented for clock index %ld\n",
clk->id);
return 0;
}
if (rate == stm32_clk_get_rate(clk))
/* already set to requested rate */
return rate;
/* get the current PLLSAIR output freq */
pllsair_rate = stm32_clk_get_pllsai_rate(priv, PLLSAIR);
best_div = pllsair_rate / rate;
/* look into pllsaidivr_table if this divider is available*/
for (i = 0 ; i < sizeof(pllsaidivr_table); i++)
if (best_div == pllsaidivr_table[i]) {
/* set pll_saidivr with found value */
clrsetbits_le32(&regs->dckcfgr,
RCC_DCKCFGR_PLLSAIDIVR_MASK,
pllsaidivr_table[i]);
return rate;
}
/*
* As no pllsaidivr value is suitable to obtain requested freq,
* test all combination of pllsaidivr * pllsair and find the one
* which give freq closest to requested rate.
*/
pllsai_vco_rate = stm32_clk_get_pllsai_vco_rate(priv);
best_diff = ULONG_MAX;
best_pllsaidivr = 0;
best_plldivr = 0;
/*
* start at index 2 of plldivr_table as divider value at index 0
* and 1 are 0)
*/
for (i = 2; i < sizeof(plldivr_table); i++) {
for (j = 0; j < sizeof(pllsaidivr_table); j++) {
div = plldivr_table[i] * pllsaidivr_table[j];
current_rate = pllsai_vco_rate / div;
/* perfect combination is found ? */
if (current_rate == rate) {
best_pllsaidivr = j;
best_plldivr = i;
found = true;
break;
}
diff = (current_rate > rate) ?
current_rate - rate : rate - current_rate;
/* found a better combination ? */
if (diff < best_diff) {
best_diff = diff;
best_pllsaidivr = j;
best_plldivr = i;
}
}
if (found)
break;
}
/* Disable the SAI PLL */
clrbits_le32(&regs->cr, RCC_CR_PLLSAION);
/* set pll_saidivr with found value */
clrsetbits_le32(&regs->dckcfgr, RCC_DCKCFGR_PLLSAIDIVR_MASK,
best_pllsaidivr << RCC_DCKCFGR_PLLSAIDIVR_SHIFT);
/* set pllsair with found value */
clrsetbits_le32(&regs->pllsaicfgr, RCC_PLLSAICFGR_PLLSAIR_MASK,
plldivr_table[best_plldivr]
<< RCC_PLLSAICFGR_PLLSAIR_SHIFT);
/* Enable the SAI PLL */
setbits_le32(&regs->cr, RCC_CR_PLLSAION);
while (!(readl(&regs->cr) & RCC_CR_PLLSAIRDY))
;
div = plldivr_table[best_plldivr] * pllsaidivr_table[best_pllsaidivr];
return pllsai_vco_rate / div;
#else
return 0;
#endif
}
static int stm32_clk_enable(struct clk *clk)