drivers/misc: add Aspeed LPC snoop driver

This driver enables the LPC snoop hardware on the ASPEED BMC
which generates an interrupt upon every write to an I/O port
by the host.

This is typically used to monitor BIOS boot progress by listening
to well-known debug port 80h.

The functionality in this commit just saves all snooped values
to a circular 2K buffer in the kernel, subsequent commits can
act on the values to do things with them.

Signed-off-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 07bbd4c..8136dc7 100644 (file)
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -490,6 +490,14 @@ config ASPEED_LPC_CTRL
          ioctl()s, the driver also provides a read/write interface to a BMC ram
          region where the host LPC read/write region can be buffered.
 
+config ASPEED_LPC_SNOOP
+       tristate "Aspeed ast2500 HOST LPC snoop support"
+       depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
+       help
+         Provides a driver to control the 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.
+
 config PCI_ENDPOINT_TEST
        depends on PCI
        select CRC32

diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 81ef3e6..b0b7664 100644 (file)
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_ECHO)            += echo/
 obj-$(CONFIG_VEXPRESS_SYSCFG)  += vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)         += cxl/
 obj-$(CONFIG_ASPEED_LPC_CTRL)  += aspeed-lpc-ctrl.o
+obj-$(CONFIG_ASPEED_LPC_SNOOP) += aspeed-lpc-snoop.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)        += pci_endpoint_test.o
 
 lkdtm-$(CONFIG_LKDTM)          += lkdtm_core.o

diff --git a/drivers/misc/aspeed-lpc-snoop.c b/drivers/misc/aspeed-lpc-snoop.c
new file mode 100644 (file)
index 0000000..5939055
--- /dev/null
+++ b/drivers/misc/aspeed-lpc-snoop.c
@@ -0,0 +1,261 @@
+/*
+ * 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, &reg))
+               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");