--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+//
+// Authors:
+// Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
+// Serge Semin <Sergey.Semin@baikalelectronics.ru>
+//
+// Baikal-T1 DW APB SPI and System Boot SPI driver
+//
+
+#include <linux/clk.h>
+#include <linux/cpumask.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/mux/consumer.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/spi/spi-mem.h>
+#include <linux/spi/spi.h>
+
+#include "spi-dw.h"
+
+#define BT1_BOOT_DIRMAP 0
+#define BT1_BOOT_REGS 1
+
+struct dw_spi_bt1 {
+ struct dw_spi dws;
+ struct clk *clk;
+ struct mux_control *mux;
+
+#ifdef CONFIG_SPI_DW_BT1_DIRMAP
+ void __iomem *map;
+ resource_size_t map_len;
+#endif
+};
+#define to_dw_spi_bt1(_ctlr) \
+ container_of(spi_controller_get_devdata(_ctlr), struct dw_spi_bt1, dws)
+
+typedef int (*dw_spi_bt1_init_cb)(struct platform_device *pdev,
+ struct dw_spi_bt1 *dwsbt1);
+
+#ifdef CONFIG_SPI_DW_BT1_DIRMAP
+
+static int dw_spi_bt1_dirmap_create(struct spi_mem_dirmap_desc *desc)
+{
+ struct dw_spi_bt1 *dwsbt1 = to_dw_spi_bt1(desc->mem->spi->controller);
+
+ if (!dwsbt1->map ||
+ !dwsbt1->dws.mem_ops.supports_op(desc->mem, &desc->info.op_tmpl))
+ return -EOPNOTSUPP;
+
+ /*
+ * Make sure the requested region doesn't go out of the physically
+ * mapped flash memory bounds and the operation is read-only.
+ */
+ if (desc->info.offset + desc->info.length > dwsbt1->map_len ||
+ desc->info.op_tmpl.data.dir != SPI_MEM_DATA_IN)
+ return -EOPNOTSUPP;
+
+ return 0;
+}
+
+/*
+ * Directly mapped SPI memory region is only accessible in the dword chunks.
+ * That's why we have to create a dedicated read-method to copy data from there
+ * to the passed buffer.
+ */
+static void dw_spi_bt1_dirmap_copy_from_map(void *to, void __iomem *from, size_t len)
+{
+ size_t shift, chunk;
+ u32 data;
+
+ /*
+ * We split the copying up into the next three stages: unaligned head,
+ * aligned body, unaligned tail.
+ */
+ shift = (size_t)from & 0x3;
+ if (shift) {
+ chunk = min_t(size_t, 4 - shift, len);
+ data = readl_relaxed(from - shift);
+ memcpy(to, &data + shift, chunk);
+ from += chunk;
+ to += chunk;
+ len -= chunk;
+ }
+
+ while (len >= 4) {
+ data = readl_relaxed(from);
+ memcpy(to, &data, 4);
+ from += 4;
+ to += 4;
+ len -= 4;
+ }
+
+ if (len) {
+ data = readl_relaxed(from);
+ memcpy(to, &data, len);
+ }
+}
+
+static ssize_t dw_spi_bt1_dirmap_read(struct spi_mem_dirmap_desc *desc,
+ u64 offs, size_t len, void *buf)
+{
+ struct dw_spi_bt1 *dwsbt1 = to_dw_spi_bt1(desc->mem->spi->controller);
+ struct dw_spi *dws = &dwsbt1->dws;
+ struct spi_mem *mem = desc->mem;
+ struct dw_spi_cfg cfg;
+ int ret;
+
+ /*
+ * Make sure the requested operation length is valid. Truncate the
+ * length if it's greater than the length of the MMIO region.
+ */
+ if (offs >= dwsbt1->map_len || !len)
+ return 0;
+
+ len = min_t(size_t, len, dwsbt1->map_len - offs);
+
+ /* Collect the controller configuration required by the operation */
+ cfg.tmode = SPI_TMOD_EPROMREAD;
+ cfg.dfs = 8;
+ cfg.ndf = 4;
+ cfg.freq = mem->spi->max_speed_hz;
+
+ /* Make sure the corresponding CS is de-asserted on transmission */
+ dw_spi_set_cs(mem->spi, false);
+
+ spi_enable_chip(dws, 0);
+
+ dw_spi_update_config(dws, mem->spi, &cfg);
+
+ spi_umask_intr(dws, SPI_INT_RXFI);
+
+ spi_enable_chip(dws, 1);
+
+ /*
+ * Enable the transparent mode of the System Boot Controller.
+ * The SPI core IO should have been locked before calling this method
+ * so noone would be touching the controller' registers during the
+ * dirmap operation.
+ */
+ ret = mux_control_select(dwsbt1->mux, BT1_BOOT_DIRMAP);
+ if (ret)
+ return ret;
+
+ dw_spi_bt1_dirmap_copy_from_map(buf, dwsbt1->map + offs, len);
+
+ mux_control_deselect(dwsbt1->mux);
+
+ dw_spi_set_cs(mem->spi, true);
+
+ ret = dw_spi_check_status(dws, true);
+
+ return ret ?: len;
+}
+
+#endif /* CONFIG_SPI_DW_BT1_DIRMAP */
+
+static int dw_spi_bt1_std_init(struct platform_device *pdev,
+ struct dw_spi_bt1 *dwsbt1)
+{
+ struct dw_spi *dws = &dwsbt1->dws;
+
+ dws->irq = platform_get_irq(pdev, 0);
+ if (dws->irq < 0)
+ return dws->irq;
+
+ dws->num_cs = 4;
+
+ /*
+ * Baikal-T1 Normal SPI Controllers don't always keep up with full SPI
+ * bus speed especially when it comes to the concurrent access to the
+ * APB bus resources. Thus we have no choice but to set a constraint on
+ * the SPI bus frequency for the memory operations which require to
+ * read/write data as fast as possible.
+ */
+ dws->max_mem_freq = 20000000U;
+
+ dw_spi_dma_setup_generic(dws);
+
+ return 0;
+}
+
+static int dw_spi_bt1_sys_init(struct platform_device *pdev,
+ struct dw_spi_bt1 *dwsbt1)
+{
+ struct resource *mem __maybe_unused;
+ struct dw_spi *dws = &dwsbt1->dws;
+
+ /*
+ * Baikal-T1 System Boot Controller is equipped with a mux, which
+ * switches between the directly mapped SPI flash access mode and
+ * IO access to the DW APB SSI registers. Note the mux controller
+ * must be setup to preserve the registers being accessible by default
+ * (on idle-state).
+ */
+ dwsbt1->mux = devm_mux_control_get(&pdev->dev, NULL);
+ if (IS_ERR(dwsbt1->mux))
+ return PTR_ERR(dwsbt1->mux);
+
+ /*
+ * Directly mapped SPI flash memory is a 16MB MMIO region, which can be
+ * used to access a peripheral memory device just by reading/writing
+ * data from/to it. Note the system APB bus will stall during each IO
+ * from/to the dirmap region until the operation is finished. So don't
+ * use it concurrently with time-critical tasks (like the SPI memory
+ * operations implemented in the DW APB SSI driver).
+ */
+#ifdef CONFIG_SPI_DW_BT1_DIRMAP
+ mem = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+ if (mem) {
+ dwsbt1->map = devm_ioremap_resource(&pdev->dev, mem);
+ if (!IS_ERR(dwsbt1->map)) {
+ dwsbt1->map_len = (mem->end - mem->start + 1);
+ dws->mem_ops.dirmap_create = dw_spi_bt1_dirmap_create;
+ dws->mem_ops.dirmap_read = dw_spi_bt1_dirmap_read;
+ } else {
+ dwsbt1->map = NULL;
+ }
+ }
+#endif /* CONFIG_SPI_DW_BT1_DIRMAP */
+
+ /*
+ * There is no IRQ, no DMA and just one CS available on the System Boot
+ * SPI controller.
+ */
+ dws->irq = IRQ_NOTCONNECTED;
+ dws->num_cs = 1;
+
+ /*
+ * Baikal-T1 System Boot SPI Controller doesn't keep up with the full
+ * SPI bus speed due to relatively slow APB bus and races for it'
+ * resources from different CPUs. The situation is worsen by a small
+ * FIFOs depth (just 8 words). It works better in a single CPU mode
+ * though, but still tends to be not fast enough at low CPU
+ * frequencies.
+ */
+ if (num_possible_cpus() > 1)
+ dws->max_mem_freq = 10000000U;
+ else
+ dws->max_mem_freq = 20000000U;
+
+ return 0;
+}
+
+static int dw_spi_bt1_probe(struct platform_device *pdev)
+{
+ dw_spi_bt1_init_cb init_func;
+ struct dw_spi_bt1 *dwsbt1;
+ struct resource *mem;
+ struct dw_spi *dws;
+ int ret;
+
+ dwsbt1 = devm_kzalloc(&pdev->dev, sizeof(struct dw_spi_bt1), GFP_KERNEL);
+ if (!dwsbt1)
+ return -ENOMEM;
+
+ dws = &dwsbt1->dws;
+
+ dws->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &mem);
+ if (IS_ERR(dws->regs))
+ return PTR_ERR(dws->regs);
+
+ dws->paddr = mem->start;
+
+ dwsbt1->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(dwsbt1->clk))
+ return PTR_ERR(dwsbt1->clk);
+
+ ret = clk_prepare_enable(dwsbt1->clk);
+ if (ret)
+ return ret;
+
+ dws->bus_num = pdev->id;
+ dws->reg_io_width = 4;
+ dws->max_freq = clk_get_rate(dwsbt1->clk);
+ if (!dws->max_freq)
+ goto err_disable_clk;
+
+ init_func = device_get_match_data(&pdev->dev);
+ ret = init_func(pdev, dwsbt1);
+ if (ret)
+ goto err_disable_clk;
+
+ pm_runtime_enable(&pdev->dev);
+
+ ret = dw_spi_add_host(&pdev->dev, dws);
+ if (ret)
+ goto err_disable_clk;
+
+ platform_set_drvdata(pdev, dwsbt1);
+
+ return 0;
+
+err_disable_clk:
+ clk_disable_unprepare(dwsbt1->clk);
+
+ return ret;
+}
+
+static int dw_spi_bt1_remove(struct platform_device *pdev)
+{
+ struct dw_spi_bt1 *dwsbt1 = platform_get_drvdata(pdev);
+
+ dw_spi_remove_host(&dwsbt1->dws);
+
+ pm_runtime_disable(&pdev->dev);
+
+ clk_disable_unprepare(dwsbt1->clk);
+
+ return 0;
+}
+
+static const struct of_device_id dw_spi_bt1_of_match[] = {
+ { .compatible = "baikal,bt1-ssi", .data = dw_spi_bt1_std_init},
+ { .compatible = "baikal,bt1-sys-ssi", .data = dw_spi_bt1_sys_init},
+ { }
+};
+MODULE_DEVICE_TABLE(of, dw_spi_bt1_of_match);
+
+static struct platform_driver dw_spi_bt1_driver = {
+ .probe = dw_spi_bt1_probe,
+ .remove = dw_spi_bt1_remove,
+ .driver = {
+ .name = "bt1-sys-ssi",
+ .of_match_table = dw_spi_bt1_of_match,
+ },
+};
+module_platform_driver(dw_spi_bt1_driver);
+
+MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");
+MODULE_DESCRIPTION("Baikal-T1 System Boot SPI Controller driver");
+MODULE_LICENSE("GPL v2");
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