linux-kernel - Re: [PATCH v3 03/15] clk: sunxi-ng: Add support for update bit

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Message-ID: <20250307001803.2e4887d7@minigeek.lan>
Date: Fri, 7 Mar 2025 00:18:03 +0000
From: Andre Przywara <andre.przywara@....com>
To: Jernej Škrabec <jernej.skrabec@...il.com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Chen-Yu Tsai
 <wens@...e.org>, Samuel Holland <samuel@...lland.org>, Philipp Zabel
 <p.zabel@...gutronix.de>, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/15] clk: sunxi-ng: Add support for update bit

On Tue, 04 Mar 2025 16:28:48 +0100
Jernej Škrabec <jernej.skrabec@...il.com> wrote:

Hi,

> Dne torek, 4. marec 2025 ob 02:27:53 Srednjeevropski standardni čas je Andre Przywara napisal(a):
> > Some clocks in the Allwinner A523 SoC contain an "update bit" (bit 27),
> > which must be set to apply any register changes, namely the mux
> > selector, the divider and the gate bit.
> > 
> > Add a new CCU feature bit to mark those clocks, and set bit 27 whenever
> > we are applying any changes.
> > 
> > Signed-off-by: Andre Przywara <andre.przywara@....com>
> > ---
> >  drivers/clk/sunxi-ng/ccu_common.h | 4 ++++
> >  drivers/clk/sunxi-ng/ccu_div.c    | 2 ++
> >  drivers/clk/sunxi-ng/ccu_gate.c   | 4 ++++
> >  drivers/clk/sunxi-ng/ccu_mux.c    | 2 ++
> >  4 files changed, 12 insertions(+)
> > 
> > diff --git a/drivers/clk/sunxi-ng/ccu_common.h b/drivers/clk/sunxi-ng/ccu_common.h
> > index 50fd268329671..d41d33bdff470 100644
> > --- a/drivers/clk/sunxi-ng/ccu_common.h
> > +++ b/drivers/clk/sunxi-ng/ccu_common.h
> > @@ -20,10 +20,14 @@
> >  #define CCU_FEATURE_KEY_FIELD		BIT(8)
> >  #define CCU_FEATURE_CLOSEST_RATE	BIT(9)
> >  #define CCU_FEATURE_DUAL_DIV		BIT(10)
> > +#define CCU_FEATURE_UPDATE_BIT27	BIT(11)  
> 
> There is no reason to have "BIT27" in the name of the macro. This is similar
> to KEY_FIELD, which is generic name and doesn't specify either key or position
> of this key field. Maybe just CCU_FEATURE_UPDATE_BIT or something equaly
> generic.

Sure, done. This was mostly in anticipation of the typical Allwinner
behaviour of introducing another update bit at a different location in
the future. But I guess we use a bitmask should that happen.

> With that fixed:
> Reviewed-by: Jernej Skrabec <jernej.skrabec@...il.com>

Many thanks!

Cheers,
Andre

> 
> Best regards,
> Jernej
> 
> >  
> >  /* MMC timing mode switch bit */
> >  #define CCU_MMC_NEW_TIMING_MODE		BIT(30)
> >  
> > +/* Some clocks need this bit to actually apply register changes */
> > +#define CCU_SUNXI_UPDATE_BIT		BIT(27)
> > +
> >  struct device_node;
> >  
> >  struct ccu_common {
> > diff --git a/drivers/clk/sunxi-ng/ccu_div.c b/drivers/clk/sunxi-ng/ccu_div.c
> > index 7f4691f09e01f..2d8b98fe4b13a 100644
> > --- a/drivers/clk/sunxi-ng/ccu_div.c
> > +++ b/drivers/clk/sunxi-ng/ccu_div.c
> > @@ -106,6 +106,8 @@ static int ccu_div_set_rate(struct clk_hw *hw, unsigned long rate,
> >  
> >  	reg = readl(cd->common.base + cd->common.reg);
> >  	reg &= ~GENMASK(cd->div.width + cd->div.shift - 1, cd->div.shift);
> > +	if (cd->common.features & CCU_FEATURE_UPDATE_BIT27)
> > +		reg |= CCU_SUNXI_UPDATE_BIT;
> >  
> >  	writel(reg | (val << cd->div.shift),
> >  	       cd->common.base + cd->common.reg);
> > diff --git a/drivers/clk/sunxi-ng/ccu_gate.c b/drivers/clk/sunxi-ng/ccu_gate.c
> > index ac52fd6bff677..0490f95781361 100644
> > --- a/drivers/clk/sunxi-ng/ccu_gate.c
> > +++ b/drivers/clk/sunxi-ng/ccu_gate.c
> > @@ -20,6 +20,8 @@ void ccu_gate_helper_disable(struct ccu_common *common, u32 gate)
> >  	spin_lock_irqsave(common->lock, flags);
> >  
> >  	reg = readl(common->base + common->reg);
> > +	if (common->features & CCU_FEATURE_UPDATE_BIT27)
> > +		reg |= CCU_SUNXI_UPDATE_BIT;
> >  	writel(reg & ~gate, common->base + common->reg);
> >  
> >  	spin_unlock_irqrestore(common->lock, flags);
> > @@ -44,6 +46,8 @@ int ccu_gate_helper_enable(struct ccu_common *common, u32 gate)
> >  	spin_lock_irqsave(common->lock, flags);
> >  
> >  	reg = readl(common->base + common->reg);
> > +	if (common->features & CCU_FEATURE_UPDATE_BIT27)
> > +		reg |= CCU_SUNXI_UPDATE_BIT;
> >  	writel(reg | gate, common->base + common->reg);
> >  
> >  	spin_unlock_irqrestore(common->lock, flags);
> > diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c
> > index d7ffbdeee9e04..82ee21e0d3a68 100644
> > --- a/drivers/clk/sunxi-ng/ccu_mux.c
> > +++ b/drivers/clk/sunxi-ng/ccu_mux.c
> > @@ -197,6 +197,8 @@ int ccu_mux_helper_set_parent(struct ccu_common *common,
> >  	/* The key field always reads as zero. */
> >  	if (common->features & CCU_FEATURE_KEY_FIELD)
> >  		reg |= CCU_MUX_KEY_VALUE;
> > +	if (common->features & CCU_FEATURE_UPDATE_BIT27)
> > +		reg |= CCU_SUNXI_UPDATE_BIT;
> >  
> >  	reg &= ~GENMASK(cm->width + cm->shift - 1, cm->shift);
> >  	writel(reg | (index << cm->shift), common->base + common->reg);
> >   
> 
> 
> 
> 
>