firmware: dcdbas: Add support for WSMT ACPI table

If the WSMT ACPI table is present and indicates that a fixed communication
buffer should be used, use the firmware-specified buffer instead of
allocating a buffer in memory for communications between the dcdbas driver
and firmare.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/drivers/firmware/dcdbas.c b/drivers/firmware/dcdbas.c
index 0bdea60c65ddbff81742b5d1a5d22c25521cfa8f..ae28e48ff7dcfd0a96a7b647b4bfd1c245c6ef20 100644 (file)
--- a/drivers/firmware/dcdbas.c
+++ b/drivers/firmware/dcdbas.c
@@ -21,6 +21,7 @@
  */
 
 #include <linux/platform_device.h>
+#include <linux/acpi.h>
 #include <linux/dma-mapping.h>
 #include <linux/errno.h>
 #include <linux/cpu.h>
@@ -41,7 +42,7 @@
 #include "dcdbas.h"
 
 #define DRIVER_NAME            "dcdbas"
-#define DRIVER_VERSION         "5.6.0-3.2"
+#define DRIVER_VERSION         "5.6.0-3.3"
 #define DRIVER_DESCRIPTION     "Dell Systems Management Base Driver"
 
 static struct platform_device *dcdbas_pdev;
@@ -49,19 +50,23 @@ static struct platform_device *dcdbas_pdev;
 static u8 *smi_data_buf;
 static dma_addr_t smi_data_buf_handle;
 static unsigned long smi_data_buf_size;
+static unsigned long max_smi_data_buf_size = MAX_SMI_DATA_BUF_SIZE;
 static u32 smi_data_buf_phys_addr;
 static DEFINE_MUTEX(smi_data_lock);
+static u8 *eps_buffer;
 
 static unsigned int host_control_action;
 static unsigned int host_control_smi_type;
 static unsigned int host_control_on_shutdown;
 
+static bool wsmt_enabled;
+
 /**
  * smi_data_buf_free: free SMI data buffer
  */
 static void smi_data_buf_free(void)
 {
-       if (!smi_data_buf)
+       if (!smi_data_buf || wsmt_enabled)
                return;
 
        dev_dbg(&dcdbas_pdev->dev, "%s: phys: %x size: %lu\n",
@@ -86,7 +91,7 @@ static int smi_data_buf_realloc(unsigned long size)
        if (smi_data_buf_size >= size)
                return 0;
 
-       if (size > MAX_SMI_DATA_BUF_SIZE)
+       if (size > max_smi_data_buf_size)
                return -EINVAL;
 
        /* new buffer is needed */
@@ -169,7 +174,7 @@ static ssize_t smi_data_write(struct file *filp, struct kobject *kobj,
 {
        ssize_t ret;
 
-       if ((pos + count) > MAX_SMI_DATA_BUF_SIZE)
+       if ((pos + count) > max_smi_data_buf_size)
                return -EINVAL;
 
        mutex_lock(&smi_data_lock);
@@ -322,8 +327,20 @@ static ssize_t smi_request_store(struct device *dev,
                        ret = count;
                break;
        case 1:
-               /* Calling Interface SMI */
-               smi_cmd->ebx = (u32) virt_to_phys(smi_cmd->command_buffer);
+               /*
+                * Calling Interface SMI
+                *
+                * Provide physical address of command buffer field within
+                * the struct smi_cmd to BIOS.
+                *
+                * Because the address that smi_cmd (smi_data_buf) points to
+                * will be from memremap() of a non-memory address if WSMT
+                * is present, we can't use virt_to_phys() on smi_cmd, so
+                * we have to use the physical address that was saved when
+                * the virtual address for smi_cmd was received.
+                */
+               smi_cmd->ebx = smi_data_buf_phys_addr +
+                               offsetof(struct smi_cmd, command_buffer);
                ret = dcdbas_smi_request(smi_cmd);
                if (!ret)
                        ret = count;
@@ -482,6 +499,93 @@ static void dcdbas_host_control(void)
        }
 }
 
+/* WSMT */
+
+static u8 checksum(u8 *buffer, u8 length)
+{
+       u8 sum = 0;
+       u8 *end = buffer + length;
+
+       while (buffer < end)
+               sum += *buffer++;
+       return sum;
+}
+
+static inline struct smm_eps_table *check_eps_table(u8 *addr)
+{
+       struct smm_eps_table *eps = (struct smm_eps_table *)addr;
+
+       if (strncmp(eps->smm_comm_buff_anchor, SMM_EPS_SIG, 4) != 0)
+               return NULL;
+
+       if (checksum(addr, eps->length) != 0)
+               return NULL;
+
+       return eps;
+}
+
+static int dcdbas_check_wsmt(void)
+{
+       struct acpi_table_wsmt *wsmt = NULL;
+       struct smm_eps_table *eps = NULL;
+       u64 remap_size;
+       u8 *addr;
+
+       acpi_get_table(ACPI_SIG_WSMT, 0, (struct acpi_table_header **)&wsmt);
+       if (!wsmt)
+               return 0;
+
+       /* Check if WSMT ACPI table shows that protection is enabled */
+       if (!(wsmt->protection_flags & ACPI_WSMT_FIXED_COMM_BUFFERS) ||
+           !(wsmt->protection_flags & ACPI_WSMT_COMM_BUFFER_NESTED_PTR_PROTECTION))
+               return 0;
+
+       /* Scan for EPS (entry point structure) */
+       for (addr = (u8 *)__va(0xf0000);
+            addr < (u8 *)__va(0x100000 - sizeof(struct smm_eps_table));
+            addr += 16) {
+               eps = check_eps_table(addr);
+               if (eps)
+                       break;
+       }
+
+       if (!eps) {
+               dev_dbg(&dcdbas_pdev->dev, "found WSMT, but no EPS found\n");
+               return -ENODEV;
+       }
+
+       /*
+        * Get physical address of buffer and map to virtual address.
+        * Table gives size in 4K pages, regardless of actual system page size.
+        */
+       if (upper_32_bits(eps->smm_comm_buff_addr + 8)) {
+               dev_warn(&dcdbas_pdev->dev, "found WSMT, but EPS buffer address is above 4GB\n");
+               return -EINVAL;
+       }
+       /*
+        * Limit remap size to MAX_SMI_DATA_BUF_SIZE + 8 (since the first 8
+        * bytes are used for a semaphore, not the data buffer itself).
+        */
+       remap_size = eps->num_of_4k_pages * PAGE_SIZE;
+       if (remap_size > MAX_SMI_DATA_BUF_SIZE + 8)
+               remap_size = MAX_SMI_DATA_BUF_SIZE + 8;
+       eps_buffer = memremap(eps->smm_comm_buff_addr, remap_size, MEMREMAP_WB);
+       if (!eps_buffer) {
+               dev_warn(&dcdbas_pdev->dev, "found WSMT, but failed to map EPS buffer\n");
+               return -ENOMEM;
+       }
+
+       /* First 8 bytes is for a semaphore, not part of the smi_data_buf */
+       smi_data_buf_phys_addr = eps->smm_comm_buff_addr + 8;
+       smi_data_buf = eps_buffer + 8;
+       smi_data_buf_size = remap_size - 8;
+       max_smi_data_buf_size = smi_data_buf_size;
+       wsmt_enabled = true;
+       dev_info(&dcdbas_pdev->dev,
+                "WSMT found, using firmware-provided SMI buffer.\n");
+       return 1;
+}
+
 /**
  * dcdbas_reboot_notify: handle reboot notification for host control
  */
@@ -548,6 +652,11 @@ static int dcdbas_probe(struct platform_device *dev)
 
        dcdbas_pdev = dev;
 
+       /* Check if ACPI WSMT table specifies protected SMI buffer address */
+       error = dcdbas_check_wsmt();
+       if (error < 0)
+               return error;
+
        /*
         * BIOS SMI calls require buffer addresses be in 32-bit address space.
         * This is done by setting the DMA mask below.
@@ -635,6 +744,8 @@ static void __exit dcdbas_exit(void)
         */
        if (dcdbas_pdev)
                smi_data_buf_free();
+       if (eps_buffer)
+               memunmap(eps_buffer);
        platform_device_unregister(dcdbas_pdev_reg);
        platform_driver_unregister(&dcdbas_driver);
 }

diff --git a/drivers/firmware/dcdbas.h b/drivers/firmware/dcdbas.h
index ca3cb0a54ab67a3f50bd22b3d579942a5a1057ae..52729a494b000e0b6337adb1d7e0e4fcb8ece35d 100644 (file)
--- a/drivers/firmware/dcdbas.h
+++ b/drivers/firmware/dcdbas.h
@@ -53,6 +53,7 @@
 #define EXPIRED_TIMER                          (0)
 
 #define SMI_CMD_MAGIC                          (0x534D4931)
+#define SMM_EPS_SIG                            "$SCB"
 
 #define DCDBAS_DEV_ATTR_RW(_name) \
        DEVICE_ATTR(_name,0600,_name##_show,_name##_store);
@@ -103,5 +104,14 @@ struct apm_cmd {
 
 int dcdbas_smi_request(struct smi_cmd *smi_cmd);
 
+struct smm_eps_table {
+       char smm_comm_buff_anchor[4];
+       u8 length;
+       u8 checksum;
+       u8 version;
+       u64 smm_comm_buff_addr;
+       u64 num_of_4k_pages;
+} __packed;
+
 #endif /* _DCDBAS_H_ */