From: Nicolas Ferre nicolas.ferre@microchip.com
[ Upstream commit af98caeaa7b6ad11eb7b7c8bfaddc769df2889f3 ]
This register is important for sequencing the commands to PLLs, so actually write the update bits with regmap_write_bits() instead of relying on a read/modify/write regmap command that could skip the actual hardware write if the value is identical to the one read.
It's changed when modification is needed to the PLL, when read-only operation is done, we could keep the call to regmap_update_bits().
Add a comment to the sam9x60_div_pll_set_div() function that uses this PLL_UPDT register so that it's used consistently, according to the product's datasheet.
Signed-off-by: Nicolas Ferre nicolas.ferre@microchip.com Tested-by: Ryan Wanner ryan.wanner@microchip.com # on sama7d65 and sam9x75 Link: https://lore.kernel.org/r/20250827150811.82496-1-nicolas.ferre@microchip.com [claudiu.beznea: fix "Alignment should match open parenthesis" checkpatch.pl check] Signed-off-by: Claudiu Beznea claudiu.beznea@tuxon.dev Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES - `regmap_update_bits()` skips the hardware write when the target value matches the current value, so repeated programming of the PLL update register could silently do nothing. The replacement with `regmap_write_bits()`—which forces the transaction by passing `force=true` down to `_regmap_update_bits()` (see `include/linux/regmap.h:1340` and `drivers/base/regmap/regmap.c:3247`)—guarantees every update command actually reaches the PMC. - The fix touches every path that modifies PLL state: the PLL enable sequence now forces the ID latch and both update pulses in `sam9x60_frac_pll_set()` (`drivers/clk/at91/clk-sam9x60-pll.c:96`, `:128`, `:136`), and the disable path does the same (`:164-175`). Without these forced writes, the “apply changes” strobes could be dropped, leaving MUL/FRAC reprogramming or ENPLL clears unapplied—manifesting as PLLs that refuse to retune or power down. - Divider programming follows the same requirement: `sam9x60_div_pll_set()`, `_unprepare()`, `_set_rate_chg()`, and the notifier all now force the ID and UPDATE pulse (`drivers/clk/at91/clk- sam9x60-pll.c:365-413`, `:528-599`). This prevents cases where DVFS notifier transitions or runtime rate changes fail because the write was skipped, which can lead to over-clocking or clocks stuck at stale divisors. - Read-only users are intentionally left on `regmap_update_bits()` (e.g. `sam9x60_div_pll_is_prepared()` at `drivers/clk/at91/clk- sam9x60-pll.c:427-434`), and the new comment at `:343-348` documents the datasheet requirement that the correct PLL ID already be latched before issuing the forced update. That keeps behaviour consistent and avoids accidental misuse. - The change is localized to the AT91 SAM9x60 PLL driver, introduces no new APIs, and simply guarantees the hardware sequencing works as documented; it has been validated on Sama7D65/Sam9x75 hardware per the Tested-by tag. The bug being fixed—lost update strobes leading to PLLs that won’t reliably enable/disable—is severe for users, while the regression risk from issuing guaranteed writes is minimal.
drivers/clk/at91/clk-sam9x60-pll.c | 75 ++++++++++++++++-------------- 1 file changed, 39 insertions(+), 36 deletions(-)
diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c index cefd9948e1039..a035dc15454b0 100644 --- a/drivers/clk/at91/clk-sam9x60-pll.c +++ b/drivers/clk/at91/clk-sam9x60-pll.c @@ -93,8 +93,8 @@ static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
spin_lock_irqsave(core->lock, flags);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_ID_MSK, core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_ID_MSK, core->id); regmap_read(regmap, AT91_PMC_PLL_CTRL1, &val); cmul = (val & core->layout->mul_mask) >> core->layout->mul_shift; cfrac = (val & core->layout->frac_mask) >> core->layout->frac_shift; @@ -128,17 +128,17 @@ static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core) udelay(10); }
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0, AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL, AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
while (!sam9x60_pll_ready(regmap, core->id)) cpu_relax(); @@ -164,8 +164,8 @@ static void sam9x60_frac_pll_unprepare(struct clk_hw *hw)
spin_lock_irqsave(core->lock, flags);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_ID_MSK, core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_ID_MSK, core->id);
regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0, AT91_PMC_PLL_CTRL0_ENPLL, 0);
@@ -173,9 +173,9 @@ static void sam9x60_frac_pll_unprepare(struct clk_hw *hw) regmap_update_bits(regmap, AT91_PMC_PLL_ACR, AT91_PMC_PLL_ACR_UTMIBG | AT91_PMC_PLL_ACR_UTMIVR, 0);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
spin_unlock_irqrestore(core->lock, flags); } @@ -262,8 +262,8 @@ static int sam9x60_frac_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate,
spin_lock_irqsave(core->lock, irqflags);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, - core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, + core->id); regmap_read(regmap, AT91_PMC_PLL_CTRL1, &val); cmul = (val & core->layout->mul_mask) >> core->layout->mul_shift; cfrac = (val & core->layout->frac_mask) >> core->layout->frac_shift; @@ -275,18 +275,18 @@ static int sam9x60_frac_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate, (frac->mul << core->layout->mul_shift) | (frac->frac << core->layout->frac_shift));
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0, AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL, AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
while (!sam9x60_pll_ready(regmap, core->id)) cpu_relax(); @@ -338,7 +338,10 @@ static const struct clk_ops sam9x60_frac_pll_ops_chg = { .restore_context = sam9x60_frac_pll_restore_context, };
-/* This function should be called with spinlock acquired. */ +/* This function should be called with spinlock acquired. + * Warning: this function must be called only if the same PLL ID was set in + * PLL_UPDT register previously. + */ static void sam9x60_div_pll_set_div(struct sam9x60_pll_core *core, u32 div, bool enable) { @@ -350,9 +353,9 @@ static void sam9x60_div_pll_set_div(struct sam9x60_pll_core *core, u32 div, core->layout->div_mask | ena_msk, (div << core->layout->div_shift) | ena_val);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
while (!sam9x60_pll_ready(regmap, core->id)) cpu_relax(); @@ -366,8 +369,8 @@ static int sam9x60_div_pll_set(struct sam9x60_pll_core *core) unsigned int val, cdiv;
spin_lock_irqsave(core->lock, flags); - regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_ID_MSK, core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_ID_MSK, core->id); regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val); cdiv = (val & core->layout->div_mask) >> core->layout->div_shift;
@@ -398,15 +401,15 @@ static void sam9x60_div_pll_unprepare(struct clk_hw *hw)
spin_lock_irqsave(core->lock, flags);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_ID_MSK, core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_ID_MSK, core->id);
regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0, core->layout->endiv_mask, 0);
- regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, - AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, - AT91_PMC_PLL_UPDT_UPDATE | core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, + AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK, + AT91_PMC_PLL_UPDT_UPDATE | core->id);
spin_unlock_irqrestore(core->lock, flags); } @@ -518,8 +521,8 @@ static int sam9x60_div_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate, div->div = DIV_ROUND_CLOSEST(parent_rate, rate) - 1;
spin_lock_irqsave(core->lock, irqflags); - regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, - core->id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, + core->id); regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val); cdiv = (val & core->layout->div_mask) >> core->layout->div_shift;
@@ -574,8 +577,8 @@ static int sam9x60_div_pll_notifier_fn(struct notifier_block *notifier, div->div = div->safe_div;
spin_lock_irqsave(core.lock, irqflags); - regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, - core.id); + regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK, + core.id); regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val); cdiv = (val & core.layout->div_mask) >> core.layout->div_shift;