diff options
Diffstat (limited to 'arch/arm/mach-mstar/mstarv7.c')
| -rw-r--r-- | arch/arm/mach-mstar/mstarv7.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/arch/arm/mach-mstar/mstarv7.c b/arch/arm/mach-mstar/mstarv7.c new file mode 100644 index 000000000..81a4cbcab --- /dev/null +++ b/arch/arm/mach-mstar/mstarv7.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Device Tree support for MStar/Sigmastar Armv7 SoCs + * + * Copyright (c) 2020 thingy.jp + * Author: Daniel Palmer <daniel@thingy.jp> + */ + +#include <linux/init.h> +#include <asm/mach/arch.h> +#include <asm/mach/map.h> +#include <linux/of.h> +#include <linux/of_address.h> +#include <linux/io.h> + +/* + * In the u-boot code the area these registers are in is + * called "L3 bridge" and there are register descriptions + * for something in the same area called "AXI". + * + * It's not exactly known what this is but the vendor code + * for both u-boot and linux share calls to "flush the miu pipe". + * This seems to be to force pending CPU writes to memory so that + * the state is right before DMA capable devices try to read + * descriptors and data the CPU has prepared. Without doing this + * ethernet doesn't work reliably for example. + */ + +#define MSTARV7_L3BRIDGE_FLUSH 0x14 +#define MSTARV7_L3BRIDGE_STATUS 0x40 +#define MSTARV7_L3BRIDGE_FLUSH_TRIGGER BIT(0) +#define MSTARV7_L3BRIDGE_STATUS_DONE BIT(12) + +static void __iomem *l3bridge; + +static const char * const mstarv7_board_dt_compat[] __initconst = { + "mstar,infinity", + "mstar,infinity3", + "mstar,mercury5", + NULL, +}; + +/* + * This may need locking to deal with situations where an interrupt + * happens while we are in here and mb() gets called by the interrupt handler. + * + * The vendor code did have a spin lock but it doesn't seem to be needed and + * removing it hasn't caused any side effects so far. + * + * [writel|readl]_relaxed have to be used here because otherwise + * we'd end up right back in here. + */ +static void mstarv7_mb(void) +{ + /* toggle the flush miu pipe fire bit */ + writel_relaxed(0, l3bridge + MSTARV7_L3BRIDGE_FLUSH); + writel_relaxed(MSTARV7_L3BRIDGE_FLUSH_TRIGGER, l3bridge + + MSTARV7_L3BRIDGE_FLUSH); + while (!(readl_relaxed(l3bridge + MSTARV7_L3BRIDGE_STATUS) + & MSTARV7_L3BRIDGE_STATUS_DONE)) { + /* wait for flush to complete */ + } +} + +static void __init mstarv7_init(void) +{ + struct device_node *np; + + np = of_find_compatible_node(NULL, NULL, "mstar,l3bridge"); + l3bridge = of_iomap(np, 0); + if (l3bridge) + soc_mb = mstarv7_mb; + else + pr_warn("Failed to install memory barrier, DMA will be broken!\n"); +} + +DT_MACHINE_START(MSTARV7_DT, "MStar/Sigmastar Armv7 (Device Tree)") + .dt_compat = mstarv7_board_dt_compat, + .init_machine = mstarv7_init, +MACHINE_END |