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