ACPI: ibm-acpi: Implement direct-ec-access thermal reading modes for up to 16 sensors

This patch extends ibm-acpi to support reading thermal sensors directly
through ACPI EC register access.  It uses a DMI match to detect ThinkPads
with a new-style embedded controller, that are known to have forward-
compatible register maps and use 0x00 to fill in non-used registers and
export thermal sensors at EC offsets 0x78-7F and 0xC0-C7.

Direct ACPI EC register access is implemented for 8-sensor and 16-sensor
new-style ThinkPad controller firmwares as an experimental feature.  The
code does some limited sanity checks on the temperatures read through EC
access, and will default to the old ACPI TMP0-7 mode if anything is amiss.

Userspace ABI is not changed for 8 sensors, but /proc/acpi/ibm/thermal is
extended for 16 sensors if the firmware supports 16 sensors.

A documentation update is also provided.

The information about the ThinkPad register map was determined by studying
ibm-acpi "ecdump" output from various ThinkPad models, submitted by
subscribers of the linux-thinkpad mailinglist.  Futher information was
gathered from the DSDT tables, as they describe the EC register map in
recent ThinkPads.

DSDT source shows that TMP0-7 access and direct register access are
actually the same thing on these firmwares, but unfortunately IBM never
did update their DSDT EC register map to export TMP8-TMP15 for the second
range of sensors.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>

1 files changed, 91 insertions, 2 deletions

diff --git a/drivers/acpi/ibm_acpi.c b/drivers/acpi/ibm_acpi.c
index baf9492f0a79..1703c617c0e8 100644
--- a/drivers/acpi/ibm_acpi.c
+++ b/drivers/acpi/ibm_acpi.c
@@ -80,6 +80,7 @@
 #include <linux/proc_fs.h>
 #include <linux/backlight.h>
 #include <asm/uaccess.h>
+#include <linux/dmi.h>
 
 #include <acpi/acpi_drivers.h>
 #include <acpi/acnamesp.h>
@@ -221,13 +222,17 @@ enum thermal_access_mode {
         IBMACPI_THERMAL_NONE = 0,       /* No thermal support */
         IBMACPI_THERMAL_ACPI_TMP07,     /* Use ACPI TMP0-7 */
         IBMACPI_THERMAL_ACPI_UPDT,      /* Use ACPI TMP0-7 with UPDT */
+        IBMACPI_THERMAL_TPEC_8,         /* Use ACPI EC regs, 8 sensors */
+        IBMACPI_THERMAL_TPEC_16,        /* Use ACPI EC regs, 16 sensors */
 };
 
-#define IBMACPI_MAX_THERMAL_SENSORS 8   /* Max thermal sensors supported */
+#define IBMACPI_MAX_THERMAL_SENSORS 16  /* Max thermal sensors supported */
 struct ibm_thermal_sensors_struct {
         s32 temp[IBMACPI_MAX_THERMAL_SENSORS];
 };
 
+static int ibm_thinkpad_ec_found;
+
 struct ibm_struct {
         char *name;
         char param[32];
@@ -1290,7 +1295,52 @@ static enum thermal_access_mode thermal_read_mode;
 
 static int thermal_init(void)
 {
-        if (acpi_evalf(ec_handle, NULL, "TMP7", "qv")) {
+        u8 t, ta1, ta2;
+        int i;
+        int acpi_tmp7 = acpi_evalf(ec_handle, NULL, "TMP7", "qv");
+
+        if (ibm_thinkpad_ec_found && experimental) {
+                /*
+                 * Direct EC access mode: sensors at registers
+                 * 0x78-0x7F, 0xC0-0xC7.  Registers return 0x00 for
+                 * non-implemented, thermal sensors return 0x80 when
+                 * not available
+                 */
+
+                ta1 = ta2 = 0;
+                for (i = 0; i < 8; i++) {
+                        if (likely(acpi_ec_read(0x78 + i, &t))) {
+                                ta1 |= t;
+                        } else {
+                                ta1 = 0;
+                                break;
+                        }
+                        if (likely(acpi_ec_read(0xC0 + i, &t))) {
+                                ta2 |= t;
+                        } else {
+                                ta1 = 0;
+                                break;
+                        }
+                }
+                if (ta1 == 0) {
+                        /* This is sheer paranoia, but we handle it anyway */
+                        if (acpi_tmp7) {
+                                printk(IBM_ERR
+                                       "ThinkPad ACPI EC access misbehaving, "
+                                       "falling back to ACPI TMPx access mode\n");
+                                thermal_read_mode = IBMACPI_THERMAL_ACPI_TMP07;
+                        } else {
+                                printk(IBM_ERR
+                                       "ThinkPad ACPI EC access misbehaving, "
+                                       "disabling thermal sensors access\n");
+                                thermal_read_mode = IBMACPI_THERMAL_NONE;
+                        }
+                } else {
+                        thermal_read_mode =
+                            (ta2 != 0) ?
+                            IBMACPI_THERMAL_TPEC_16 : IBMACPI_THERMAL_TPEC_8;
+                }
+        } else if (acpi_tmp7) {
                 if (acpi_evalf(ec_handle, NULL, "UPDT", "qv")) {
                         /* 600e/x, 770e, 770x */
                         thermal_read_mode = IBMACPI_THERMAL_ACPI_UPDT;
@@ -1309,12 +1359,30 @@ static int thermal_init(void)
 static int thermal_get_sensors(struct ibm_thermal_sensors_struct *s)
 {
         int i, t;
+        s8 tmp;
         char tmpi[] = "TMPi";
 
         if (!s)
                 return -EINVAL;
 
         switch (thermal_read_mode) {
+#if IBMACPI_MAX_THERMAL_SENSORS >= 16
+        case IBMACPI_THERMAL_TPEC_16:
+                for (i = 0; i < 8; i++) {
+                        if (!acpi_ec_read(0xC0 + i, &tmp))
+                                return -EIO;
+                        s->temp[i + 8] = tmp * 1000;
+                }
+                /* fallthrough */
+#endif
+        case IBMACPI_THERMAL_TPEC_8:
+                for (i = 0; i < 8; i++) {
+                        if (!acpi_ec_read(0x78 + i, &tmp))
+                                return -EIO;
+                        s->temp[i] = tmp * 1000;
+                }
+                return (thermal_read_mode == IBMACPI_THERMAL_TPEC_16) ? 16 : 8;
+
         case IBMACPI_THERMAL_ACPI_UPDT:
                 if (!acpi_evalf(ec_handle, NULL, "UPDT", "v"))
                         return -EIO;
@@ -2052,6 +2120,24 @@ static void acpi_ibm_exit(void)
         remove_proc_entry(IBM_DIR, acpi_root_dir);
 }
 
+static int __init check_dmi_for_ec(void)
+{
+        struct dmi_device *dev = NULL;
+
+        /*
+         * ThinkPad T23 or newer, A31 or newer, R50e or newer,
+         * X32 or newer, all Z series;  Some models must have an
+         * up-to-date BIOS or they will not be detected.
+         *
+         * See http://thinkwiki.org/wiki/List_of_DMI_IDs
+         */
+        while ((dev = dmi_find_device(DMI_DEV_TYPE_OEM_STRING, NULL, dev))) {
+                if (strstr(dev->name, "IBM ThinkPad Embedded Controller"))
+                        return 1;
+        }
+        return 0;
+}
+
 static int __init acpi_ibm_init(void)
 {
         int ret, i;
@@ -2071,6 +2157,9 @@ static int __init acpi_ibm_init(void)
                 return -ENODEV;
         }
 
+        /* Models with newer firmware report the EC in DMI */
+        ibm_thinkpad_ec_found = check_dmi_for_ec();
+
         /* these handles are not required */
         IBM_HANDLE_INIT(vid);
         IBM_HANDLE_INIT(vid2);