Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1305803 > unrolled thread

[PATCH v2] clk: mediatek: Allow changing PLL rate when it is off

Back to article view | Back to linux.kernel

Contents

  [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off James Liao <jamesjj.liao@mediatek.com> - 2016-01-11 04:40 +0100
    Re: [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off Michael Turquette <mturquette@baylibre.com> - 2016-01-14 03:30 +0100
      Re: [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off James Liao <jamesjj.liao@mediatek.com> - 2016-01-14 07:00 +0100

#1305803 — [PATCH v2] clk: mediatek: Allow changing PLL rate when it is off

Some modules may need to change its clock rate before turn on it.
So changing PLL's rate when it is off should be allowed.
This patch removes PLL enabled check before set rate, so that
PLLs can set new frequency even if they are off.

On MT8173 for example, ARMPLL's enable bit can be controlled by
other HW. That means ARMPLL may be turned on even if we (CPU / SW)
set ARMPLL's enable bit as 0. In this case, SW may want and can
still change ARMPLL's rate by changing its pcw and postdiv settings.
But without this patch, new pcw setting will not be applied because
its enable bit is 0.

Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
---
 drivers/clk/mediatek/clk-pll.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
index 966cab1..8e31fae 100644
--- a/drivers/clk/mediatek/clk-pll.c
+++ b/drivers/clk/mediatek/clk-pll.c
@@ -91,9 +91,6 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
 		int postdiv)
 {
 	u32 con1, val;
-	int pll_en;
-
-	pll_en = readl(pll->base_addr + REG_CON0) & CON0_BASE_EN;
 
 	/* set postdiv */
 	val = readl(pll->pd_addr);
@@ -114,15 +111,13 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
 
 	con1 = readl(pll->base_addr + REG_CON1);
 
-	if (pll_en)
-		con1 |= CON0_PCW_CHG;
+	con1 |= CON0_PCW_CHG;
 
 	writel(con1, pll->base_addr + REG_CON1);
 	if (pll->tuner_addr)
 		writel(con1 + 1, pll->tuner_addr);
 
-	if (pll_en)
-		udelay(20);
+	udelay(20);
 }
 
 /*
-- 
1.9.1

[toc] | [next] | [standalone]

#1308965

Hi James,

Quoting James Liao (2016-01-10 19:28:56)
> Some modules may need to change its clock rate before turn on it.
> So changing PLL's rate when it is off should be allowed.
> This patch removes PLL enabled check before set rate, so that
> PLLs can set new frequency even if they are off.
> 
> On MT8173 for example, ARMPLL's enable bit can be controlled by
> other HW. That means ARMPLL may be turned on even if we (CPU / SW)
> set ARMPLL's enable bit as 0. In this case, SW may want and can
> still change ARMPLL's rate by changing its pcw and postdiv settings.
> But without this patch, new pcw setting will not be applied because
> its enable bit is 0.

Must the clock signal be enabled to change the PLL rate? If so, does
ARMPLL set the CLK_SET_RATE_GATE flag?

> 
> Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
> ---
>  drivers/clk/mediatek/clk-pll.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> index 966cab1..8e31fae 100644
> --- a/drivers/clk/mediatek/clk-pll.c
> +++ b/drivers/clk/mediatek/clk-pll.c
> @@ -91,9 +91,6 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
>                 int postdiv)
>  {
>         u32 con1, val;
> -       int pll_en;
> -
> -       pll_en = readl(pll->base_addr + REG_CON0) & CON0_BASE_EN;
>  
>         /* set postdiv */
>         val = readl(pll->pd_addr);
> @@ -114,15 +111,13 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
>  
>         con1 = readl(pll->base_addr + REG_CON1);
>  
> -       if (pll_en)
> -               con1 |= CON0_PCW_CHG;
> +       con1 |= CON0_PCW_CHG;

This unconditionally enables the PLL whenever clk_set_rate is called,
changing the previous behavior. The clk framework still tracks the
intent of ARMPLLs users with the enable_count. How about something like
the following:

	bool pll_en = clk_hw_is_enabled(&pll->hw);

	if (pll_en)
		con1 |= CON0_PCW_CHG;

	writel(con1, pll->base_addr + REG_CON1);
	if (pll->tuner_addr)
		writel(con1 + 1, pll->tuner_addr);

	if (pll_en)
		udelay(20);

This does not rely on the hardware to tell us the intent of the user,
but instead on our framework usecounting.

Regards,
Mike

>         writel(con1, pll->base_addr + REG_CON1);
>         if (pll->tuner_addr)
>                 writel(con1 + 1, pll->tuner_addr);
>  
> -       if (pll_en)
> -               udelay(20);
> +       udelay(20);
>  }
>  
>  /*
> -- 
> 1.9.1
> 

[toc] | [prev] | [next] | [standalone]

#1309036

Hi Mike,

On Wed, 2016-01-13 at 18:26 -0800, Michael Turquette wrote:
> Hi James,
> 
> Quoting James Liao (2016-01-10 19:28:56)
> > Some modules may need to change its clock rate before turn on it.
> > So changing PLL's rate when it is off should be allowed.
> > This patch removes PLL enabled check before set rate, so that
> > PLLs can set new frequency even if they are off.
> > 
> > On MT8173 for example, ARMPLL's enable bit can be controlled by
> > other HW. That means ARMPLL may be turned on even if we (CPU / SW)
> > set ARMPLL's enable bit as 0. In this case, SW may want and can
> > still change ARMPLL's rate by changing its pcw and postdiv settings.
> > But without this patch, new pcw setting will not be applied because
> > its enable bit is 0.
> 
> Must the clock signal be enabled to change the PLL rate? If so, does
> ARMPLL set the CLK_SET_RATE_GATE flag?

No. The controlling of PLL's rate and enable are independent. So we can
change the PLL's rate when it's enabled or disabled.

> > 
> > Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
> > ---
> >  drivers/clk/mediatek/clk-pll.c | 9 ++-------
> >  1 file changed, 2 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/clk/mediatek/clk-pll.c b/drivers/clk/mediatek/clk-pll.c
> > index 966cab1..8e31fae 100644
> > --- a/drivers/clk/mediatek/clk-pll.c
> > +++ b/drivers/clk/mediatek/clk-pll.c
> > @@ -91,9 +91,6 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
> >                 int postdiv)
> >  {
> >         u32 con1, val;
> > -       int pll_en;
> > -
> > -       pll_en = readl(pll->base_addr + REG_CON0) & CON0_BASE_EN;
> >  
> >         /* set postdiv */
> >         val = readl(pll->pd_addr);
> > @@ -114,15 +111,13 @@ static void mtk_pll_set_rate_regs(struct mtk_clk_pll *pll, u32 pcw,
> >  
> >         con1 = readl(pll->base_addr + REG_CON1);
> >  
> > -       if (pll_en)
> > -               con1 |= CON0_PCW_CHG;
> > +       con1 |= CON0_PCW_CHG;
> 
> This unconditionally enables the PLL whenever clk_set_rate is called,
> changing the previous behavior. The clk framework still tracks the
> intent of ARMPLLs users with the enable_count. How about something like
> the following:

Not really. This patch will not enable or disable PLL when we change its
rate. The PLL enable bit is bit[0], we didn't change bit[0] in
mtk_pll_set_rate_regs(), so its state will not be changed.

This patch set CON0_PCW_CHG (bit[31]) no matter the PLL is enabled or
not. So we don't need to check the enable bit[0] nor PLL state in the
framework before set bit[31].

> 	bool pll_en = clk_hw_is_enabled(&pll->hw);
> 
> 	if (pll_en)
> 		con1 |= CON0_PCW_CHG;
> 
> 	writel(con1, pll->base_addr + REG_CON1);
> 	if (pll->tuner_addr)
> 		writel(con1 + 1, pll->tuner_addr);
> 
> 	if (pll_en)
> 		udelay(20);
> 
> This does not rely on the hardware to tell us the intent of the user,
> but instead on our framework usecounting.


Best regards,

James

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web