[PATCH v3 4/5] arm: mach-k3: j721e-init.c: Add support for CONFIG_K3_OPP_LOW

[Aniket Limaye]

From: Reid Tonking <reidt at ti.com>

The default j7200 devicetree and k3_avs driver set 2GHz/1GHz frequency
for A72/MSMC clks and the OPP_NOM voltage.

J7200 SOCs may support OPP_LOW Operating Performance Point:
1GHz/500MHz clks for A72/MSMC and OPP_LOW AVS voltage read from efuse.

Hence, add a config check to select OPP_LOW specs:
- Check if OPP_LOW AVS voltage read from efuse is valid.
- Update the clock frequencies in devicetree.
- Program the OPP_LOW AVS voltage for VDD_CPU.

Signed-off-by: Reid Tonking <reidt at ti.com>
Signed-off-by: Aniket Limaye <a-limaye at ti.com>

---
v3:
- Use more descriptive name for fdt_fixup_a72ss_clock_frequency()
  and make function static.
- Add error codes to prints.
- Move error prints (with error codes) before else conditions. Helps
  with code readability to map error print with the function.
- Remove k3_avs_set_opp() from here altogether. Reasoning being that the
  value being set through k3_avs_set_opp() will anyway be (correctly)
  overridden by the k3_avs_notify_freq() call later in the boot process,
  when a72 freq is actually set from clk_k3.
- Link to v2: https://lore.kernel.org/u-boot/20241023130033.1826413-5-a-limaye@ti.com/

v2:
- Fix indentation in fix_freq()
- Remove the efuse data check addition from this commit, as it's not
  related to adding support for CONFIG_K3_OPP_LOW. The same addition
  was moved to the previous patch in this series.
- Link to v1: https://lore.kernel.org/u-boot/20241017062911.2241167-5-a-limaye@ti.com/

---
 arch/arm/mach-k3/j721e/j721e_init.c | 41 ++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-k3/j721e/j721e_init.c b/arch/arm/mach-k3/j721e/j721e_init.c
index e9ed8cb267c..8d8c4a1c538 100644
--- a/arch/arm/mach-k3/j721e/j721e_init.c
+++ b/arch/arm/mach-k3/j721e/j721e_init.c
@@ -19,6 +19,7 @@
 #include <fdtdec.h>
 #include <mmc.h>
 #include <remoteproc.h>
+#include <k3-avs.h>
 
 #include "../sysfw-loader.h"
 #include "../common.h"
@@ -147,6 +148,34 @@ static void setup_navss_nb(void)
 	writel(NB_THREADMAP_BIT1, (uintptr_t)NAVSS0_NBSS_NB1_CFG_NB_THREADMAP);
 }
 
+#if defined(CONFIG_CPU_V7R) && defined(CONFIG_K3_AVS0)
+static int fdt_fixup_a72ss_clock_frequency(const void *fdt)
+{
+	int node, ret;
+	u32 opp_low_freq[3];
+
+	node = fdt_node_offset_by_compatible(fdt, -1, "ti,am654-rproc");
+	if (node < 0) {
+		printf("%s: A72 not found\n", __func__);
+		return node;
+	}
+
+	/* j7200 opp low values according to data sheet */
+	opp_low_freq[0] = cpu_to_fdt32(1000000000); /* 202-2 -> A72SS0_CORE0_0_ARM_CLK */
+	opp_low_freq[1] = cpu_to_fdt32(200000000); /* 61-1 -> GTC0_GTC_CLK */
+	opp_low_freq[2] = cpu_to_fdt32(500000000); /* 4-1 -> A72SS0_CORE0_MSMC_CLK */
+
+	ret = fdt_setprop((void *)fdt, node, "assigned-clock-rates",
+			  opp_low_freq, sizeof(opp_low_freq));
+	if (ret) {
+		printf("%s: Can not set value\n", __func__);
+		return ret;
+	}
+
+	return 0;
+}
+#endif
+
 /*
  * This uninitialized global variable would normal end up in the .bss section,
  * but the .bss is cleared between writing and reading this variable, so move
@@ -301,8 +330,18 @@ void board_init_f(ulong dummy)
 #if defined(CONFIG_CPU_V7R) && defined(CONFIG_K3_AVS0)
 	ret = uclass_get_device_by_driver(UCLASS_MISC, DM_DRIVER_GET(k3_avs),
 					  &dev);
-	if (ret)
+	if (ret) {
 		printf("AVS init failed: %d\n", ret);
+	} else if (IS_ENABLED(CONFIG_K3_OPP_LOW)) {
+		ret = k3_check_opp(dev, J721E_VDD_MPU, AM6_OPP_LOW);
+		if (ret) {
+			printf("OPP_LOW: k3_check_opp failed: %d\n", ret);
+		} else {
+			ret = fdt_fixup_a72ss_clock_frequency(gd->fdt_blob);
+			if (ret)
+				printf("OPP_LOW: fdt_fixup_a72ss_clock_frequency failed: %d\n", ret);
+		}
+	}
 #endif
 
 #if defined(CONFIG_K3_J721E_DDRSS)
-- 
2.47.0