clk: baikal-t1: Move reset-controls code into a dedicated module

Before adding the directly controlled resets support it's reasonable to
move the existing resets control functionality into a dedicated object for
the sake of the CCU dividers clock driver simplification. After the new
functionality was added clk-ccu-div.c would have got to a mixture of the
weakly dependent clocks and resets methods. Splitting the methods up into
the two objects will make the code easier to read and maintain. It shall
also improve the code scalability (though hopefully we won't need this
part that much in the future).

The reset control functionality is now implemented in the framework of a
single unit since splitting it up doesn't make much sense due to
relatively simple reset operations. The ccu-rst.c has been designed to be
looking like ccu-div.c or ccu-pll.c with two globally available methods
for the sake of the code unification and better code readability.

This commit doesn't provide any change in the CCU reset implementation
semantics. As before the driver will support the trigger-like CCU resets
only, which are responsible for the AXI-bus, APB-bus and SATA-ref blocks
reset. The assert/de-assert-capable reset controls support will be added
in the next commit.

Note the CCU Clock dividers and resets functionality split up was possible
due to not having any side-effects (at least we didn't found ones) of the
regmap-based concurrent access of the common CCU dividers/reset CSRs.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20220929225402.9696-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 151 insertions, 0 deletions

diff --git a/drivers/clk/baikal-t1/ccu-rst.c b/drivers/clk/baikal-t1/ccu-rst.c
new file mode 100644
index 000000000000..7db52633270f
--- /dev/null
+++ b/drivers/clk/baikal-t1/ccu-rst.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 BAIKAL ELECTRONICS, JSC
+ *
+ * Authors:
+ *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
+ *
+ * Baikal-T1 CCU Resets interface driver
+ */
+
+#define pr_fmt(fmt) "bt1-ccu-rst: " fmt
+
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/printk.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/slab.h>
+
+#include <dt-bindings/reset/bt1-ccu.h>
+
+#include "ccu-rst.h"
+
+#define CCU_AXI_MAIN_BASE		0x030
+#define CCU_AXI_DDR_BASE		0x034
+#define CCU_AXI_SATA_BASE		0x038
+#define CCU_AXI_GMAC0_BASE		0x03C
+#define CCU_AXI_GMAC1_BASE		0x040
+#define CCU_AXI_XGMAC_BASE		0x044
+#define CCU_AXI_PCIE_M_BASE		0x048
+#define CCU_AXI_PCIE_S_BASE		0x04C
+#define CCU_AXI_USB_BASE		0x050
+#define CCU_AXI_HWA_BASE		0x054
+#define CCU_AXI_SRAM_BASE		0x058
+
+#define CCU_SYS_SATA_REF_BASE		0x060
+#define CCU_SYS_APB_BASE		0x064
+
+#define CCU_RST_DELAY_US		1
+
+#define CCU_RST_TRIG(_base, _ofs)		\
+	{					\
+		.base = _base,			\
+		.mask = BIT(_ofs),		\
+	}
+
+struct ccu_rst_info {
+	unsigned int base;
+	unsigned int mask;
+};
+
+/*
+ * Each AXI-bus clock divider is equipped with the corresponding clock-consumer
+ * domain reset (it's self-deasserted reset control).
+ */
+static const struct ccu_rst_info axi_rst_info[] = {
+	[CCU_AXI_MAIN_RST] = CCU_RST_TRIG(CCU_AXI_MAIN_BASE, 1),
+	[CCU_AXI_DDR_RST] = CCU_RST_TRIG(CCU_AXI_DDR_BASE, 1),
+	[CCU_AXI_SATA_RST] = CCU_RST_TRIG(CCU_AXI_SATA_BASE, 1),
+	[CCU_AXI_GMAC0_RST] = CCU_RST_TRIG(CCU_AXI_GMAC0_BASE, 1),
+	[CCU_AXI_GMAC1_RST] = CCU_RST_TRIG(CCU_AXI_GMAC1_BASE, 1),
+	[CCU_AXI_XGMAC_RST] = CCU_RST_TRIG(CCU_AXI_XGMAC_BASE, 1),
+	[CCU_AXI_PCIE_M_RST] = CCU_RST_TRIG(CCU_AXI_PCIE_M_BASE, 1),
+	[CCU_AXI_PCIE_S_RST] = CCU_RST_TRIG(CCU_AXI_PCIE_S_BASE, 1),
+	[CCU_AXI_USB_RST] = CCU_RST_TRIG(CCU_AXI_USB_BASE, 1),
+	[CCU_AXI_HWA_RST] = CCU_RST_TRIG(CCU_AXI_HWA_BASE, 1),
+	[CCU_AXI_SRAM_RST] = CCU_RST_TRIG(CCU_AXI_SRAM_BASE, 1),
+};
+
+/*
+ * SATA reference clock domain and APB-bus domain are connected with the
+ * sefl-deasserted reset control, which can be activated via the corresponding
+ * clock divider register. DDR and PCIe sub-domains can be reset with directly
+ * controlled reset signals. Resetting the DDR controller though won't end up
+ * well while the Linux kernel is working.
+ */
+static const struct ccu_rst_info sys_rst_info[] = {
+	[CCU_SYS_SATA_REF_RST] = CCU_RST_TRIG(CCU_SYS_SATA_REF_BASE, 1),
+	[CCU_SYS_APB_RST] = CCU_RST_TRIG(CCU_SYS_APB_BASE, 1),
+};
+
+static int ccu_rst_reset(struct reset_controller_dev *rcdev, unsigned long idx)
+{
+	struct ccu_rst *rst = to_ccu_rst(rcdev);
+	const struct ccu_rst_info *info = &rst->rsts_info[idx];
+
+	regmap_update_bits(rst->sys_regs, info->base, info->mask, info->mask);
+
+	/* The next delay must be enough to cover all the resets. */
+	udelay(CCU_RST_DELAY_US);
+
+	return 0;
+}
+
+static const struct reset_control_ops ccu_rst_ops = {
+	.reset = ccu_rst_reset,
+};
+
+struct ccu_rst *ccu_rst_hw_register(const struct ccu_rst_init_data *rst_init)
+{
+	struct ccu_rst *rst;
+	int ret;
+
+	if (!rst_init)
+		return ERR_PTR(-EINVAL);
+
+	rst = kzalloc(sizeof(*rst), GFP_KERNEL);
+	if (!rst)
+		return ERR_PTR(-ENOMEM);
+
+	rst->sys_regs = rst_init->sys_regs;
+	if (of_device_is_compatible(rst_init->np, "baikal,bt1-ccu-axi")) {
+		rst->rcdev.nr_resets = ARRAY_SIZE(axi_rst_info);
+		rst->rsts_info = axi_rst_info;
+	} else if (of_device_is_compatible(rst_init->np, "baikal,bt1-ccu-sys")) {
+		rst->rcdev.nr_resets = ARRAY_SIZE(sys_rst_info);
+		rst->rsts_info = sys_rst_info;
+	} else {
+		pr_err("Incompatible DT node '%s' specified\n",
+		       of_node_full_name(rst_init->np));
+		ret = -EINVAL;
+		goto err_kfree_rst;
+	}
+
+	rst->rcdev.owner = THIS_MODULE;
+	rst->rcdev.ops = &ccu_rst_ops;
+	rst->rcdev.of_node = rst_init->np;
+
+	ret = reset_controller_register(&rst->rcdev);
+	if (ret) {
+		pr_err("Couldn't register '%s' reset controller\n",
+		       of_node_full_name(rst_init->np));
+		goto err_kfree_rst;
+	}
+
+	return rst;
+
+err_kfree_rst:
+	kfree(rst);
+
+	return ERR_PTR(ret);
+}
+
+void ccu_rst_hw_unregister(struct ccu_rst *rst)
+{
+	reset_controller_unregister(&rst->rcdev);
+
+	kfree(rst);
+}