Messages in this thread Patch in this message | | | From | Baolin Wang <> | Subject | [PATCH v3] mfd: syscon: Add Spreadtrum physical regmap bus support | Date | Tue, 21 Apr 2020 22:13:25 +0800 |
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Some platforms such as Spreadtrum platform, define a special method to update bits of the registers instead of read-modify-write, which means we should use a physical regmap bus to define the reg_update_bits() operation instead of the MMIO regmap bus. Thus we can register a new physical regmap bus into syscon core to support this.
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com> --- Changes from v2: - Fix building errors without enabling CONFIG_ARCH_SPRD.
Changes from v1: - Add WARN_ONCE() for seting bits and clearing bits at the same time. - Remove the Spreadtrum SoC syscon driver, instead moving the regmap_bus instance into syscon.c driver.
Changes from RFC v2: - Drop regmap change, which was applied by Mark. - Add more information about how to use set/clear. - Add checking to ensure the platform is compatible with using a new physical regmap bus.
Changes from RFC v1: - Add new helper to registers a physical regmap bus instead of using the MMIO bus. --- drivers/mfd/syscon.c | 83 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 81 insertions(+), 2 deletions(-)
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index 3a97816d0cba..ca91b7770e1a 100644 --- a/drivers/mfd/syscon.c +++ b/drivers/mfd/syscon.c @@ -40,6 +40,72 @@ static const struct regmap_config syscon_regmap_config = { .reg_stride = 4, }; +#if IS_ENABLED(CONFIG_ARCH_SPRD) +#define SPRD_REG_SET_OFFSET 0x1000 +#define SPRD_REG_CLR_OFFSET 0x2000 + +/* + * The Spreadtrum platform defines a special set/clear method to update + * registers' bits, which means it can write values to the register's SET + * address (offset is 0x1000) to set bits, and write values to the register's + * CLEAR address (offset is 0x2000) to clear bits. + * + * This set/clear method can help to remove the race of accessing the global + * registers between the multiple subsystems instead of using hardware + * spinlocks. + * + * Note: there is a potential risk when users want to set and clear bits + * at the same time, since the set/clear method will always do bits setting + * before bits clearing, which may cause some unexpected results if the + * operation sequence is strict. Thus we recommend that do not set and + * clear bits at the same time if you are not sure about the results. + */ +static int sprd_syscon_update_bits(void *context, unsigned int reg, + unsigned int mask, unsigned int val) +{ + void __iomem *base = context; + unsigned int set, clr; + + set = val & mask; + clr = ~set & mask; + + if (set) + writel(set, base + reg + SPRD_REG_SET_OFFSET); + + if (clr) + writel(clr, base + reg + SPRD_REG_CLR_OFFSET); + + WARN_ONCE(set && clr, "%s: non-atomic update", __func__); + return 0; +} + +static int sprd_syscon_read(void *context, unsigned int reg, unsigned int *val) +{ + void __iomem *base = context; + + *val = readl(base + reg); + return 0; +} + +static int sprd_syscon_write(void *context, unsigned int reg, unsigned int val) +{ + void __iomem *base = context; + + writel(val, base + reg); + return 0; +} +#endif + +static struct regmap_bus sprd_syscon_regmap_bus = { +#if IS_ENABLED(CONFIG_ARCH_SPRD) + .fast_io = true, + .reg_write = sprd_syscon_write, + .reg_read = sprd_syscon_read, + .reg_update_bits = sprd_syscon_update_bits, + .val_format_endian_default = REGMAP_ENDIAN_LITTLE, +#endif +}; + static struct syscon *of_syscon_register(struct device_node *np, bool check_clk) { struct clk *clk; @@ -50,6 +116,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk) int ret; struct regmap_config syscon_config = syscon_regmap_config; struct resource res; + bool use_phy_regmap_bus = false; syscon = kzalloc(sizeof(*syscon), GFP_KERNEL); if (!syscon) @@ -106,14 +173,26 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk) syscon_config.val_bits = reg_io_width * 8; syscon_config.max_register = resource_size(&res) - reg_io_width; - regmap = regmap_init_mmio(NULL, base, &syscon_config); + /* + * The Spreadtrum syscon need register a real physical regmap bus + * with new atomic bits updating operation instead of using + * read-modify-write. + */ + if (IS_ENABLED(CONFIG_ARCH_SPRD) && + of_device_is_compatible(np, "sprd,atomic-syscon")) { + use_phy_regmap_bus = true; + regmap = regmap_init(NULL, &sprd_syscon_regmap_bus, base, + &syscon_config); + } else { + regmap = regmap_init_mmio(NULL, base, &syscon_config); + } if (IS_ERR(regmap)) { pr_err("regmap init failed\n"); ret = PTR_ERR(regmap); goto err_regmap; } - if (check_clk) { + if (!use_phy_regmap_bus && check_clk) { clk = of_clk_get(np, 0); if (IS_ERR(clk)) { ret = PTR_ERR(clk); -- 2.17.1
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