power: pmic: sunxi: introduce generic SPL AXP DC/DC driver

So far we had a separate driver file for each AXP PMIC chip that we need
to support in the SPL. The code in there was largely similar, but
differed in many details.

Based on the idea of the DM AXP driver, introduce a data structure to
describe each regulator in a compact way. This is a simplified version
of the struct used in the DM driver, as we don't need to support the full
voltage range and not every regulator in the SPL.
For now we only support the DC/DC buck converters, since that's what we
need the SPL to configure, mostly. Also we get rid of the regulator name,
and hardcode the regulator number by its position in the array (first is
DCDC1, second is DCDC2, etc). We also drop support for the value table,
we ideally won't need that for the subset of regulators required.
At the end each regulator is described by a 10 bytes struct, so we avoid
blowing up the SPL footprint, but still can use generic code.

Each chip is supposed to be described separately, and protected by
ifdef's, to only build in the regulators needed for a particular board.
We also describe the bits to help identifying the AXP chip, and the
shutdown details in that section.

Add a generic driver, that exports axp_set_dcdc<x>() functions to set up
the buck converters. For now this just contains the bits for the (new)
AXP717, but it's not wired up anywhere yet.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

diff --git a/drivers/power/axp_spl.c b/drivers/power/axp_spl.c
new file mode 100644 (file)
index 0000000..0382d91
--- /dev/null
+++ b/drivers/power/axp_spl.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * AXP PMIC SPL driver
+ * (C) Copyright 2024 Arm Ltd.
+ */
+
+#include <errno.h>
+#include <linux/types.h>
+#include <asm/arch/pmic_bus.h>
+#include <axp_pmic.h>
+
+struct axp_reg_desc_spl {
+       u8      enable_reg;
+       u8      enable_mask;
+       u8      volt_reg;
+       u8      volt_mask;
+       u16     min_mV;
+       u16     max_mV;
+       u8      step_mV;
+       u8      split;
+};
+
+#define NA 0xff
+
+#if defined(CONFIG_AXP717_POWER)                               /* AXP717 */
+
+static const struct axp_reg_desc_spl axp_spl_dcdc_regulators[] = {
+       { 0x80, BIT(0), 0x83, 0x7f,  500, 1540,  10, 70 },
+       { 0x80, BIT(1), 0x84, 0x7f,  500, 1540,  10, 70 },
+       { 0x80, BIT(2), 0x85, 0x7f,  500, 1840,  10, 70 },
+};
+
+#define AXP_CHIP_VERSION       0x0
+#define AXP_CHIP_VERSION_MASK  0x0
+#define AXP_CHIP_ID            0x0
+#define AXP_SHUTDOWN_REG       0x27
+#define AXP_SHUTDOWN_MASK      BIT(0)
+
+#else
+
+       #error "Please define the regulator registers in axp_spl_regulators[]."
+
+#endif
+
+static u8 axp_mvolt_to_cfg(int mvolt, const struct axp_reg_desc_spl *reg)
+{
+       if (mvolt < reg->min_mV)
+               mvolt = reg->min_mV;
+       else if (mvolt > reg->max_mV)
+               mvolt = reg->max_mV;
+
+       mvolt -= reg->min_mV;
+
+       /* voltage in the first range ? */
+       if (mvolt <= reg->split * reg->step_mV)
+               return mvolt / reg->step_mV;
+
+       mvolt -= reg->split * reg->step_mV;
+
+       return reg->split + mvolt / (reg->step_mV * 2);
+}
+
+static int axp_set_dcdc(int dcdc_num, unsigned int mvolt)
+{
+       const struct axp_reg_desc_spl *reg;
+       int ret;
+
+       if (dcdc_num < 1 || dcdc_num > ARRAY_SIZE(axp_spl_dcdc_regulators))
+               return -EINVAL;
+
+       reg = &axp_spl_dcdc_regulators[dcdc_num - 1];
+
+       if (mvolt == 0)
+               return pmic_bus_clrbits(reg->enable_reg, reg->enable_mask);
+
+       ret = pmic_bus_write(reg->volt_reg, axp_mvolt_to_cfg(mvolt, reg));
+       if (ret)
+               return ret;
+
+       return pmic_bus_setbits(reg->enable_reg, reg->enable_mask);
+}
+
+int axp_set_dcdc1(unsigned int mvolt)
+{
+       return axp_set_dcdc(1, mvolt);
+}
+
+int axp_set_dcdc2(unsigned int mvolt)
+{
+       return axp_set_dcdc(2, mvolt);
+}
+
+int axp_set_dcdc3(unsigned int mvolt)
+{
+       return axp_set_dcdc(3, mvolt);
+}
+
+int axp_set_dcdc4(unsigned int mvolt)
+{
+       return axp_set_dcdc(4, mvolt);
+}
+
+int axp_set_dcdc5(unsigned int mvolt)
+{
+       return axp_set_dcdc(5, mvolt);
+}
+
+int axp_init(void)
+{
+       int ret = pmic_bus_init();
+
+       if (ret)
+               return ret;
+
+       if (AXP_CHIP_VERSION_MASK) {
+               u8 axp_chip_id;
+
+               ret = pmic_bus_read(AXP_CHIP_VERSION, &axp_chip_id);
+               if (ret)
+                       return ret;
+
+               if ((axp_chip_id & AXP_CHIP_VERSION_MASK) != AXP_CHIP_ID) {
+                       debug("unknown PMIC: 0x%x\n", axp_chip_id);
+                       return -EINVAL;
+               }
+       }
+
+       return 0;
+}
+
+#if !CONFIG_IS_ENABLED(ARM_PSCI_FW) && !IS_ENABLED(CONFIG_SYSRESET_CMD_POWEROFF)
+int do_poweroff(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
+{
+       pmic_bus_setbits(AXP_SHUTDOWN_REG, AXP_SHUTDOWN_MASK);
+
+       /* infinite loop during shutdown */
+       while (1)
+               ;
+
+       /* not reached */
+       return 0;
+}
+#endif