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// 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
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