[PATCH 0/2] Fix rate rounding for Meson read-only dividers

[PATCH 0/2] Fix rate rounding for Meson read-only dividers

[Carlo Caione]

Meson read-only dividers can round a requested rate using a divisor they
cannot program. The clock core may then adjust child clocks using the
wrong parent rate.

This series uses the divisor already set in hardware. The first patch
adds a missing /4 entry to the GXL and G12A HDMI divider tables so that
all their register values can be read correctly.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
---
Carlo Caione (2):
      clk: meson: add the missing HDMI divider /4 alias
      clk: meson: regmap: use the current divisor for read-only clocks

 drivers/clk/meson/clk-regmap.c | 34 +++++++++++++++++++++-------------
 drivers/clk/meson/g12a.c       |  3 ++-
 drivers/clk/meson/gxbb.c       |  3 ++-
 3 files changed, 25 insertions(+), 15 deletions(-)
---
base-commit: 363f97a1ce635b86be7fd263d56a040fbd87bdbb
change-id: 20261026-upstream-clk-regmap-ro-divider-f9ee3532fbe1

Best regards,
--  
Carlo Caione <ccaione@baylibre.com>


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[PATCH 1/2] clk: meson: add the missing HDMI divider /4 alias

[Carlo Caione]

On GXL and G12A, HDMI PLL divider values 2 and 3 both select /4, but
only value 2 is listed in the tables. Reading value 3 therefore gives
an unknown divisor and an incorrect clock rate.

Add value 3 to both tables. This also avoids a division by zero when
the read-only rate-rounding helper uses the value read from hardware.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
---
 drivers/clk/meson/g12a.c | 3 ++-
 drivers/clk/meson/gxbb.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/meson/g12a.c b/drivers/clk/meson/g12a.c
index d0d4c7b6dc82..b23b9514fa91 100644
--- a/drivers/clk/meson/g12a.c
+++ b/drivers/clk/meson/g12a.c
@@ -779,12 +779,13 @@ static struct clk_regmap g12a_hdmi_pll_dco = {
 
 /*
  * G12/SM1 hdmi OD dividers are POWER_OF_TWO dividers but limited to /4.
- * A divider value of 3 should map to /8 but instead map /4 so ignore it.
+ * Divider values 2 and 3 both select /4.
  */
 static const struct clk_div_table g12a_hdmi_pll_od_div_table[] = {
 	{ .val = 0, .div = 1 },
 	{ .val = 1, .div = 2 },
 	{ .val = 2, .div = 4 },
+	{ .val = 3, .div = 4 },
 	{ /* sentinel */ }
 };
 
diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
index 7a7b104182ff..8cb6404c0efd 100644
--- a/drivers/clk/meson/gxbb.c
+++ b/drivers/clk/meson/gxbb.c
@@ -350,12 +350,13 @@ static struct clk_regmap gxbb_hdmi_pll = {
 
 /*
  * GXL hdmi OD dividers are POWER_OF_TWO dividers but limited to /4.
- * A divider value of 3 should map to /8 but instead map /4 so ignore it.
+ * Divider values 2 and 3 both select /4.
  */
 static const struct clk_div_table gxl_hdmi_pll_od_div_table[] = {
 	{ .val = 0, .div = 1 },
 	{ .val = 1, .div = 2 },
 	{ .val = 2, .div = 4 },
+	{ .val = 3, .div = 4 },
 	{ /* sentinel */ }
 };
 

-- 
2.56.0


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[PATCH 2/2] clk: meson: regmap: use the current divisor for read-only clocks

[Carlo Caione]

None of the Meson clocks using clk_regmap_divider_ro_ops set
CLK_DIVIDER_READ_ONLY. Without that flag, the shared rounding callback
can choose a new divisor even though these ops cannot program it. The
clock core may then adjust child clocks using the wrong parent rate.

Make the read-only ops always round using the current hardware divisor.
Parent rate changes remain allowed with CLK_SET_RATE_PARENT.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
---
 drivers/clk/meson/clk-regmap.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/clk/meson/clk-regmap.c b/drivers/clk/meson/clk-regmap.c
index 1ed56fe63cae..002e16865109 100644
--- a/drivers/clk/meson/clk-regmap.c
+++ b/drivers/clk/meson/clk-regmap.c
@@ -120,26 +120,34 @@ static unsigned long clk_regmap_div_recalc_rate(struct clk_hw *hw,
 				   div->width);
 }
 
-static int clk_regmap_div_determine_rate(struct clk_hw *hw,
-					 struct clk_rate_request *req)
+static int clk_regmap_div_ro_determine_rate(struct clk_hw *hw,
+					    struct clk_rate_request *req)
 {
 	struct clk_regmap *clk = to_clk_regmap(hw);
 	struct clk_regmap_div_data *div = clk_get_regmap_div_data(clk);
 	unsigned int val;
 	int ret;
 
-	/* if read only, just return current value */
-	if (div->flags & CLK_DIVIDER_READ_ONLY) {
-		ret = regmap_read(clk->map, div->offset, &val);
-		if (ret)
-			return ret;
+	ret = regmap_read(clk->map, div->offset, &val);
+	if (ret)
+		return ret;
 
-		val >>= div->shift;
-		val &= clk_div_mask(div->width);
+	val >>= div->shift;
+	val &= clk_div_mask(div->width);
 
-		return divider_ro_determine_rate(hw, req, div->table,
-						 div->width, div->flags, val);
-	}
+	return divider_ro_determine_rate(hw, req, div->table, div->width,
+					 div->flags, val);
+}
+
+static int clk_regmap_div_determine_rate(struct clk_hw *hw,
+					 struct clk_rate_request *req)
+{
+	struct clk_regmap *clk = to_clk_regmap(hw);
+	struct clk_regmap_div_data *div = clk_get_regmap_div_data(clk);
+
+	/* if read only, just return current value */
+	if (div->flags & CLK_DIVIDER_READ_ONLY)
+		return clk_regmap_div_ro_determine_rate(hw, req);
 
 	return divider_determine_rate(hw, req, div->table, div->width,
 				      div->flags);
@@ -176,7 +184,7 @@ EXPORT_SYMBOL_NS_GPL(clk_regmap_divider_ops, "CLK_MESON");
 const struct clk_ops clk_regmap_divider_ro_ops = {
 	.init = clk_regmap_init,
 	.recalc_rate = clk_regmap_div_recalc_rate,
-	.determine_rate = clk_regmap_div_determine_rate,
+	.determine_rate = clk_regmap_div_ro_determine_rate,
 };
 EXPORT_SYMBOL_NS_GPL(clk_regmap_divider_ro_ops, "CLK_MESON");
 

-- 
2.56.0


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Re: [PATCH 1/2] clk: meson: add the missing HDMI divider /4 alias

[Jerome Brunet]

> On GXL and G12A, HDMI PLL divider values 2 and 3 both select /4, but
> only value 2 is listed in the tables. Reading value 3 therefore gives
> an unknown divisor and an incorrect clock rate.
> 
> Add value 3 to both tables. This also avoids a division by zero when
> the read-only rate-rounding helper uses the value read from hardware.
> 
> Signed-off-by: Carlo Caione <ccaione@baylibre.com>
> ---
>  drivers/clk/meson/g12a.c | 3 ++-
>  drivers/clk/meson/gxbb.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/meson/g12a.c b/drivers/clk/meson/g12a.c
> index d0d4c7b6dc82..b23b9514fa91 100644
> --- a/drivers/clk/meson/g12a.c
> +++ b/drivers/clk/meson/g12a.c
> @@ -779,12 +779,13 @@ static struct clk_regmap g12a_hdmi_pll_dco = {
>  
>  /*
>   * G12/SM1 hdmi OD dividers are POWER_OF_TWO dividers but limited to /4.
> - * A divider value of 3 should map to /8 but instead map /4 so ignore it.
> + * Divider values 2 and 3 both select /4.
>   */
>  static const struct clk_div_table g12a_hdmi_pll_od_div_table[] = {
>  	{ .val = 0, .div = 1 },
>  	{ .val = 1, .div = 2 },
>  	{ .val = 2, .div = 4 },
> +	{ .val = 3, .div = 4 },
>  	{ /* sentinel */ }
>  };
>  
> diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
> index 7a7b104182ff..8cb6404c0efd 100644
> --- a/drivers/clk/meson/gxbb.c
> +++ b/drivers/clk/meson/gxbb.c
> @@ -350,12 +350,13 @@ static struct clk_regmap gxbb_hdmi_pll = {
>  
>  /*
>   * GXL hdmi OD dividers are POWER_OF_TWO dividers but limited to /4.
> - * A divider value of 3 should map to /8 but instead map /4 so ignore it.
> + * Divider values 2 and 3 both select /4.
>   */
>  static const struct clk_div_table gxl_hdmi_pll_od_div_table[] = {
>  	{ .val = 0, .div = 1 },
>  	{ .val = 1, .div = 2 },
>  	{ .val = 2, .div = 4 },
> +	{ .val = 3, .div = 4 },
>  	{ /* sentinel */ }
>  };
>  

Could you split the 2 changes so you can add an approriate fixes tag
on them ?

A part from this

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>

-- 
Jerome


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Re: [PATCH 2/2] clk: meson: regmap: use the current divisor for read-only clocks

[Jerome Brunet]

> None of the Meson clocks using clk_regmap_divider_ro_ops set
> CLK_DIVIDER_READ_ONLY. Without that flag, the shared rounding callback
> can choose a new divisor even though these ops cannot program it. The
> clock core may then adjust child clocks using the wrong parent rate.
> 
> Make the read-only ops always round using the current hardware divisor.
> Parent rate changes remain allowed with CLK_SET_RATE_PARENT.
> 
> Signed-off-by: Carlo Caione <ccaione@baylibre.com>

Fixes tag maybe ?

With this

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>

-- 
Jerome


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