[RFC PATCH] clk: meson: gxbb: remove the "cpu_clk"

[Martin Blumenstingl]

It seems that the "cpu_clk" was carried over from the meson8b clock
controller driver. On Meson GX (GXBB/GXL/GXM) the registers which are
used by the cpu_clk have a different purpose (in other words: they don't
control the CPU clock anymore). HHI_SYS_CPU_CLK_CNTL1 bits 31:24 are
reserved according to the public S905 datasheet, while bit 23 is the
"A53_trace_clk_DIS" gate (which according to the datasheet should only
be used in case a silicon bug is discovered) and bits 22:20 are a
divider (A53_trace_clk). The meson clk-cpu code however expects that
bits 28:20 are reserved for a divider (according to the public S805
datasheet this "SCALE_DIV: This value represents an N+1 divider of the
input clock.").

The CPU clock on Meson GX SoCs is provided by the SCPI DVFS clock
driver instead. Two examples from a Meson GXL S905X SoC:
- vcpu (SCPI DVFS clock 0) rate: 1000000000 / cpu_clk rate: 708000000
- vcpu (SCPI DVFS clock 0) rate: 1512000000 / cpu_clk rate: 708000000

Unfortunately the CLKID_CPUCLK was already exported (but is currently
not used) to DT.

This is an RFC because I would like to hear other people's opinion on
how to clean up the CLKID_CPUCLK (as it leaves a "hole" in
gxbb_hw_onecell_data and changes the DT API (by removing a currently
unused #define).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
---
 drivers/clk/meson/gxbb.c              | 44 +++--------------------------------
 drivers/clk/meson/gxbb.h              |  2 +-
 include/dt-bindings/clock/gxbb-clkc.h |  1 -
 3 files changed, 4 insertions(+), 43 deletions(-)

diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
index 1c1ec137a3cc..06586fe16ce3 100644
--- a/drivers/clk/meson/gxbb.c
+++ b/drivers/clk/meson/gxbb.c
@@ -496,21 +496,10 @@ static struct meson_clk_mpll gxbb_mpll2 = {
 };
 
 /*
- * FIXME cpu clocks and the legacy composite clocks (e.g. clk81) are both PLL
- * post-dividers and should be modeled with their respective PLLs via the
- * forthcoming coordinated clock rates feature
+ * FIXME The legacy composite clocks (e.g. clk81) are both PLL post-dividers
+ * and should be modeled with their respective PLLs via the forthcoming
+ * coordinated clock rates feature
  */
-static struct meson_clk_cpu gxbb_cpu_clk = {
-	.reg_off = HHI_SYS_CPU_CLK_CNTL1,
-	.div_table = cpu_div_table,
-	.clk_nb.notifier_call = meson_clk_cpu_notifier_cb,
-	.hw.init = &(struct clk_init_data){
-		.name = "cpu_clk",
-		.ops = &meson_clk_cpu_ops,
-		.parent_names = (const char *[]){ "sys_pll" },
-		.num_parents = 1,
-	},
-};
 
 static u32 mux_table_clk81[]	= { 6, 5, 7 };
 
@@ -698,7 +687,6 @@ static MESON_GATE(gxbb_ao_i2c, HHI_GCLK_AO, 4);
 static struct clk_hw_onecell_data gxbb_hw_onecell_data = {
 	.hws = {
 		[CLKID_SYS_PLL]		    = &gxbb_sys_pll.hw,
-		[CLKID_CPUCLK]		    = &gxbb_cpu_clk.hw,
 		[CLKID_HDMI_PLL]	    = &gxbb_hdmi_pll.hw,
 		[CLKID_FIXED_PLL]	    = &gxbb_fixed_pll.hw,
 		[CLKID_FCLK_DIV2]	    = &gxbb_fclk_div2.hw,
@@ -925,9 +913,6 @@ static int gxbb_clkc_probe(struct platform_device *pdev)
 	for (i = 0; i < ARRAY_SIZE(gxbb_clk_mplls); i++)
 		gxbb_clk_mplls[i]->base = clk_base;
 
-	/* Populate the base address for CPU clk */
-	gxbb_cpu_clk.base = clk_base;
-
 	/* Populate the base address for the MPEG clks */
 	gxbb_mpeg_clk_sel.reg = clk_base + (u64)gxbb_mpeg_clk_sel.reg;
 	gxbb_mpeg_clk_div.reg = clk_base + (u64)gxbb_mpeg_clk_div.reg;
@@ -950,29 +935,6 @@ static int gxbb_clkc_probe(struct platform_device *pdev)
 			goto iounmap;
 	}
 
-	/*
-	 * Register CPU clk notifier
-	 *
-	 * FIXME this is wrong for a lot of reasons. First, the muxes should be
-	 * struct clk_hw objects. Second, we shouldn't program the muxes in
-	 * notifier handlers. The tricky programming sequence will be handled
-	 * by the forthcoming coordinated clock rates mechanism once that
-	 * feature is released.
-	 *
-	 * Furthermore, looking up the parent this way is terrible. At some
-	 * point we will stop allocating a default struct clk when registering
-	 * a new clk_hw, and this hack will no longer work. Releasing the ccr
-	 * feature before that time solves the problem :-)
-	 */
-	parent_hw = clk_hw_get_parent(&gxbb_cpu_clk.hw);
-	parent_clk = parent_hw->clk;
-	ret = clk_notifier_register(parent_clk, &gxbb_cpu_clk.clk_nb);
-	if (ret) {
-		pr_err("%s: failed to register clock notifier for cpu_clk\n",
-				__func__);
-		goto iounmap;
-	}
-
 	return of_clk_add_hw_provider(dev->of_node, of_clk_hw_onecell_get,
 			&gxbb_hw_onecell_data);
 
diff --git a/drivers/clk/meson/gxbb.h b/drivers/clk/meson/gxbb.h
index cbd62e46bb5b..ca1285acb92d 100644
--- a/drivers/clk/meson/gxbb.h
+++ b/drivers/clk/meson/gxbb.h
@@ -169,7 +169,7 @@
  * to be exposed to client nodes in DT: include/dt-bindings/clock/gxbb-clkc.h
  */
 #define CLKID_SYS_PLL		  0
-/* CLKID_CPUCLK */
+/* CLKID_CPUCLK - not used in the driver anymore */
 /* CLKID_HDMI_PLL */
 #define CLKID_FIXED_PLL		  3
 /* CLKID_FCLK_DIV2 */
diff --git a/include/dt-bindings/clock/gxbb-clkc.h b/include/dt-bindings/clock/gxbb-clkc.h
index 63f4c2c44a1f..07311dfdba83 100644
--- a/include/dt-bindings/clock/gxbb-clkc.h
+++ b/include/dt-bindings/clock/gxbb-clkc.h
@@ -5,7 +5,6 @@
 #ifndef __GXBB_CLKC_H
 #define __GXBB_CLKC_H
 
-#define CLKID_CPUCLK		1
 #define CLKID_HDMI_PLL		2
 #define CLKID_FCLK_DIV2		4
 #define CLKID_FCLK_DIV3		5
-- 
2.12.1