[PATCH V2 0/4] clk: imx: pll14/sccg use relaxed API

[PATCH V2 0/4] clk: imx: pll14/sccg use relaxed API

[Peng Fan]

From: Peng Fan <peng.fan@nxp.com>

V2:
 update commit message to reflect the change
 Merged sccg/composite-8m into one patchset

This patchset is insipred from Will Deacon's slide/video:
https://elinux.org/images/a/a8/Uh-oh-Its-IO-Ordering-Will-Deacon-Arm.pdf
https://www.youtube.com/watch?v=i6DayghhA8Q

Peng Fan (4):
  clk: imx: pll14xx: use writel_relaxed
  clk: imx: pll14xx: use readl to force write completed
  clk: imx: sccg: use relaxed io api
  clk: imx: composite-8m: use relaxed io api

 drivers/clk/imx/clk-composite-8m.c |  8 ++++----
 drivers/clk/imx/clk-pll14xx.c      |  8 +++++++-
 drivers/clk/imx/clk-sccg-pll.c     | 17 +++++++++--------
 3 files changed, 20 insertions(+), 13 deletions(-)

-- 
2.16.4

[PATCH V2 1/4] clk: imx: pll14xx: use writel_relaxed

[Peng Fan]

From: Peng Fan <peng.fan@nxp.com>

writel has a barrier, however that barrier is not needed,
because device memory mapping is nGnRE mapping and access is
in order and clk driver has spin lock or other lock to make
sure write finished.

Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/clk/imx/clk-pll14xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index 5778f3bfb339..5b7d41d43b3b 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -199,7 +199,7 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 
 	/* Enable BYPASS */
 	tmp |= BYPASS_MASK;
-	writel(tmp, pll->base);
+	writel_relaxed(tmp, pll->base);
 
 	div_val = (rate->mdiv << MDIV_SHIFT) | (rate->pdiv << PDIV_SHIFT) |
 		(rate->sdiv << SDIV_SHIFT);
-- 
2.16.4

[PATCH V2 2/4] clk: imx: pll14xx: use readl to force write completed

[Peng Fan]

From: Peng Fan <peng.fan@nxp.com>

To ensure writes to clock registers have properly completed,
add a readl after writel_relaxed. Then we could make sure
when udelay, write has been completed.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Will Deacon <will@kernel.org>
---
 drivers/clk/imx/clk-pll14xx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index 5b7d41d43b3b..a8af949f0848 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -205,6 +205,12 @@ static int clk_pll1416x_set_rate(struct clk_hw *hw, unsigned long drate,
 		(rate->sdiv << SDIV_SHIFT);
 	writel_relaxed(div_val, pll->base + 0x4);
 
+	/*
+	 * readl will force write completed. There is a udelay below,
+	 * we need make sure before udelay, write has been completed
+	 */
+	readl(pll->base + 0x4);
+
 	/*
 	 * According to SPEC, t3 - t2 need to be greater than
 	 * 1us and 1/FREF, respectively.
-- 
2.16.4

[PATCH V2 3/4] clk: imx: sccg: use relaxed io api

[Peng Fan]

From: Peng Fan <peng.fan@nxp.com>

writel/readl has a barrier, however that barrier is not needed,
because device memory mapping is nGnRE mapping and access is
in order and clk driver has spin lock or other lock to make
sure write finished. It is ok to use relaxed api here, no need
to use stronger readl/writel

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/clk/imx/clk-sccg-pll.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/imx/clk-sccg-pll.c b/drivers/clk/imx/clk-sccg-pll.c
index 2cf874813458..e03f8acb1e82 100644
--- a/drivers/clk/imx/clk-sccg-pll.c
+++ b/drivers/clk/imx/clk-sccg-pll.c
@@ -106,8 +106,9 @@ static int clk_sccg_pll_wait_lock(struct clk_sccg_pll *pll)
 
 	/* don't wait for lock if all plls are bypassed */
 	if (!(val & SSCG_PLL_BYPASS2_MASK))
-		return readl_poll_timeout(pll->base, val, val & PLL_LOCK_MASK,
-						0, PLL_SCCG_LOCK_TIMEOUT);
+		return readl_relaxed_poll_timeout(pll->base, val,
+						  val & PLL_LOCK_MASK,
+						  0, PLL_SCCG_LOCK_TIMEOUT);
 
 	return 0;
 }
@@ -349,7 +350,7 @@ static unsigned long clk_sccg_pll_recalc_rate(struct clk_hw *hw,
 
 	temp64 = parent_rate;
 
-	val = readl(pll->base + PLL_CFG0);
+	val = readl_relaxed(pll->base + PLL_CFG0);
 	if (val & SSCG_PLL_BYPASS2_MASK) {
 		temp64 = parent_rate;
 	} else if (val & SSCG_PLL_BYPASS1_MASK) {
@@ -372,10 +373,10 @@ static int clk_sccg_pll_set_rate(struct clk_hw *hw, unsigned long rate,
 	u32 val;
 
 	/* set bypass here too since the parent might be the same */
-	val = readl(pll->base + PLL_CFG0);
+	val = readl_relaxed(pll->base + PLL_CFG0);
 	val &= ~SSCG_PLL_BYPASS_MASK;
 	val |= FIELD_PREP(SSCG_PLL_BYPASS_MASK, setup->bypass);
-	writel(val, pll->base + PLL_CFG0);
+	writel_relaxed(val, pll->base + PLL_CFG0);
 
 	val = readl_relaxed(pll->base + PLL_CFG2);
 	val &= ~(PLL_DIVF1_MASK | PLL_DIVF2_MASK);
@@ -396,7 +397,7 @@ static u8 clk_sccg_pll_get_parent(struct clk_hw *hw)
 	u32 val;
 	u8 ret = pll->parent;
 
-	val = readl(pll->base + PLL_CFG0);
+	val = readl_relaxed(pll->base + PLL_CFG0);
 	if (val & SSCG_PLL_BYPASS2_MASK)
 		ret = pll->bypass2;
 	else if (val & SSCG_PLL_BYPASS1_MASK)
@@ -409,10 +410,10 @@ static int clk_sccg_pll_set_parent(struct clk_hw *hw, u8 index)
 	struct clk_sccg_pll *pll = to_clk_sccg_pll(hw);
 	u32 val;
 
-	val = readl(pll->base + PLL_CFG0);
+	val = readl_relaxed(pll->base + PLL_CFG0);
 	val &= ~SSCG_PLL_BYPASS_MASK;
 	val |= FIELD_PREP(SSCG_PLL_BYPASS_MASK, pll->setup.bypass);
-	writel(val, pll->base + PLL_CFG0);
+	writel_relaxed(val, pll->base + PLL_CFG0);
 
 	return clk_sccg_pll_wait_lock(pll);
 }
-- 
2.16.4

[PATCH V2 4/4] clk: imx: composite-8m: use relaxed io api

[Peng Fan]

From: Peng Fan <peng.fan@nxp.com>

writel/readl has a barrier, however that barrier is not needed,
because device memory mapping is nGnRE mapping and access is
in order and clk driver has spin lock or other lock to make
sure write finished. It is ok to use relaxed api here, no need
to use stronger readl/writel

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/clk/imx/clk-composite-8m.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/imx/clk-composite-8m.c b/drivers/clk/imx/clk-composite-8m.c
index 20f7c91c03d2..513dc57483d0 100644
--- a/drivers/clk/imx/clk-composite-8m.c
+++ b/drivers/clk/imx/clk-composite-8m.c
@@ -31,14 +31,14 @@ static unsigned long imx8m_clk_composite_divider_recalc_rate(struct clk_hw *hw,
 	unsigned int prediv_value;
 	unsigned int div_value;
 
-	prediv_value = readl(divider->reg) >> divider->shift;
+	prediv_value = readl_relaxed(divider->reg) >> divider->shift;
 	prediv_value &= clk_div_mask(divider->width);
 
 	prediv_rate = divider_recalc_rate(hw, parent_rate, prediv_value,
 						NULL, divider->flags,
 						divider->width);
 
-	div_value = readl(divider->reg) >> PCG_DIV_SHIFT;
+	div_value = readl_relaxed(divider->reg) >> PCG_DIV_SHIFT;
 	div_value &= clk_div_mask(PCG_DIV_WIDTH);
 
 	return divider_recalc_rate(hw, prediv_rate, div_value, NULL,
@@ -104,13 +104,13 @@ static int imx8m_clk_composite_divider_set_rate(struct clk_hw *hw,
 
 	spin_lock_irqsave(divider->lock, flags);
 
-	val = readl(divider->reg);
+	val = readl_relaxed(divider->reg);
 	val &= ~((clk_div_mask(divider->width) << divider->shift) |
 			(clk_div_mask(PCG_DIV_WIDTH) << PCG_DIV_SHIFT));
 
 	val |= (u32)(prediv_value  - 1) << divider->shift;
 	val |= (u32)(div_value - 1) << PCG_DIV_SHIFT;
-	writel(val, divider->reg);
+	writel_relaxed(val, divider->reg);
 
 	spin_unlock_irqrestore(divider->lock, flags);
 
-- 
2.16.4

RE: [PATCH V2 0/4] clk: imx: pll14/sccg use relaxed API

[Peng Fan]

> Subject: [PATCH V2 0/4] clk: imx: pll14/sccg use relaxed API

Any comments?

Thanks,
Peng.

> 
> From: Peng Fan <peng.fan@nxp.com>
> 
> V2:
>  update commit message to reflect the change  Merged sccg/composite-8m
> into one patchset
> 
> This patchset is insipred from Will Deacon's slide/video:
> https://elinux.org/images/a/a8/Uh-oh-Its-IO-Ordering-Will-Deacon-Arm.pdf
> https://www.youtube.com/watch?v=i6DayghhA8Q
> 
> Peng Fan (4):
>   clk: imx: pll14xx: use writel_relaxed
>   clk: imx: pll14xx: use readl to force write completed
>   clk: imx: sccg: use relaxed io api
>   clk: imx: composite-8m: use relaxed io api
> 
>  drivers/clk/imx/clk-composite-8m.c |  8 ++++----
>  drivers/clk/imx/clk-pll14xx.c      |  8 +++++++-
>  drivers/clk/imx/clk-sccg-pll.c     | 17 +++++++++--------
>  3 files changed, 20 insertions(+), 13 deletions(-)
> 
> --
> 2.16.4