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/*
* Copyright 2017 Google Inc
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Provides a simple driver to control the ASPEED LPC snoop interface which
* allows the BMC to listen on and save the data written by
* the host to an arbitrary LPC I/O port.
*
* Typically used by the BMC to "watch" host boot progress via port
* 0x80 writes made by the BIOS during the boot process.
*/
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/kfifo.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#define DEVICE_NAME "aspeed-lpc-snoop"
#define NUM_SNOOP_CHANNELS 2
#define SNOOP_FIFO_SIZE 2048
#define HICR5 0x0
#define HICR5_EN_SNP0W BIT(0)
#define HICR5_ENINT_SNP0W BIT(1)
#define HICR5_EN_SNP1W BIT(2)
#define HICR5_ENINT_SNP1W BIT(3)
#define HICR6 0x4
#define HICR6_STR_SNP0W BIT(0)
#define HICR6_STR_SNP1W BIT(1)
#define SNPWADR 0x10
#define SNPWADR_CH0_MASK GENMASK(15, 0)
#define SNPWADR_CH0_SHIFT 0
#define SNPWADR_CH1_MASK GENMASK(31, 16)
#define SNPWADR_CH1_SHIFT 16
#define SNPWDR 0x14
#define SNPWDR_CH0_MASK GENMASK(7, 0)
#define SNPWDR_CH0_SHIFT 0
#define SNPWDR_CH1_MASK GENMASK(15, 8)
#define SNPWDR_CH1_SHIFT 8
#define HICRB 0x80
#define HICRB_ENSNP0D BIT(14)
#define HICRB_ENSNP1D BIT(15)
struct aspeed_lpc_snoop {
struct regmap *regmap;
int irq;
struct kfifo snoop_fifo[NUM_SNOOP_CHANNELS];
};
/* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
static void put_fifo_with_discard(struct kfifo *fifo, u8 val)
{
if (!kfifo_initialized(fifo))
return;
if (kfifo_is_full(fifo))
kfifo_skip(fifo);
kfifo_put(fifo, val);
}
static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
{
struct aspeed_lpc_snoop *lpc_snoop = arg;
u32 reg, data;
if (regmap_read(lpc_snoop->regmap, HICR6, ®))
return IRQ_NONE;
/* Check if one of the snoop channels is interrupting */
reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
if (!reg)
return IRQ_NONE;
/* Ack pending IRQs */
regmap_write(lpc_snoop->regmap, HICR6, reg);
/* Read and save most recent snoop'ed data byte to FIFO */
regmap_read(lpc_snoop->regmap, SNPWDR, &data);
if (reg & HICR6_STR_SNP0W) {
u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
put_fifo_with_discard(&lpc_snoop->snoop_fifo[0], val);
}
if (reg & HICR6_STR_SNP1W) {
u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
put_fifo_with_discard(&lpc_snoop->snoop_fifo[1], val);
}
return IRQ_HANDLED;
}
static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
int rc;
lpc_snoop->irq = platform_get_irq(pdev, 0);
if (!lpc_snoop->irq)
return -ENODEV;
rc = devm_request_irq(dev, lpc_snoop->irq,
aspeed_lpc_snoop_irq, IRQF_SHARED,
DEVICE_NAME, lpc_snoop);
if (rc < 0) {
dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
lpc_snoop->irq = 0;
return rc;
}
return 0;
}
static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
int channel, u16 lpc_port)
{
int rc = 0;
u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
/* Create FIFO datastructure */
rc = kfifo_alloc(&lpc_snoop->snoop_fifo[channel],
SNOOP_FIFO_SIZE, GFP_KERNEL);
if (rc)
return rc;
/* Enable LPC snoop channel at requested port */
switch (channel) {
case 0:
hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
snpwadr_mask = SNPWADR_CH0_MASK;
snpwadr_shift = SNPWADR_CH0_SHIFT;
hicrb_en = HICRB_ENSNP0D;
break;
case 1:
hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
snpwadr_mask = SNPWADR_CH1_MASK;
snpwadr_shift = SNPWADR_CH1_SHIFT;
hicrb_en = HICRB_ENSNP1D;
break;
default:
return -EINVAL;
}
regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
lpc_port << snpwadr_shift);
regmap_update_bits(lpc_snoop->regmap, HICRB, hicrb_en, hicrb_en);
return rc;
}
static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
int channel)
{
switch (channel) {
case 0:
regmap_update_bits(lpc_snoop->regmap, HICR5,
HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
0);
break;
case 1:
regmap_update_bits(lpc_snoop->regmap, HICR5,
HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
0);
break;
default:
return;
}
kfifo_free(&lpc_snoop->snoop_fifo[channel]);
}
static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
{
struct aspeed_lpc_snoop *lpc_snoop;
struct device *dev;
u32 port;
int rc;
dev = &pdev->dev;
lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
if (!lpc_snoop)
return -ENOMEM;
lpc_snoop->regmap = syscon_node_to_regmap(
pdev->dev.parent->of_node);
if (IS_ERR(lpc_snoop->regmap)) {
dev_err(dev, "Couldn't get regmap\n");
return -ENODEV;
}
dev_set_drvdata(&pdev->dev, lpc_snoop);
rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
if (rc) {
dev_err(dev, "no snoop ports configured\n");
return -ENODEV;
}
rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
if (rc)
return rc;
rc = aspeed_lpc_enable_snoop(lpc_snoop, 0, port);
if (rc)
return rc;
/* Configuration of 2nd snoop channel port is optional */
if (of_property_read_u32_index(dev->of_node, "snoop-ports",
1, &port) == 0) {
rc = aspeed_lpc_enable_snoop(lpc_snoop, 1, port);
if (rc)
aspeed_lpc_disable_snoop(lpc_snoop, 0);
}
return rc;
}
static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
{
struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
/* Disable both snoop channels */
aspeed_lpc_disable_snoop(lpc_snoop, 0);
aspeed_lpc_disable_snoop(lpc_snoop, 1);
return 0;
}
static const struct of_device_id aspeed_lpc_snoop_match[] = {
{ .compatible = "aspeed,ast2500-lpc-snoop" },
{ },
};
static struct platform_driver aspeed_lpc_snoop_driver = {
.driver = {
.name = DEVICE_NAME,
.of_match_table = aspeed_lpc_snoop_match,
},
.probe = aspeed_lpc_snoop_probe,
.remove = aspeed_lpc_snoop_remove,
};
module_platform_driver(aspeed_lpc_snoop_driver);
MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
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