platform/x86: apple-gmux: Add apple_gmux_detect() helper

Add a new (static inline) apple_gmux_detect() helper to apple-gmux.h
which can be used for gmux detection instead of apple_gmux_present().

The latter is not really reliable since an ACPI device with a HID
of APP000B is present on some devices without a gmux at all, as well
as on devices with a newer (unsupported) MMIO based gmux model.

This causes apple_gmux_present() to return false-positives on
a number of different Apple laptop models.

This new helper uses the same probing as the actual apple-gmux
driver, so that it does not return false positives.

To avoid code duplication the gmux_probe() function of the actual
driver is also moved over to using the new apple_gmux_detect() helper.

This avoids false positives (vs _HID + IO region detection) on:

MacBookPro5,4
https://pastebin.com/8Xjq7RhS

MacBookPro8,1
https://linux-hardware.org/?probe=e513cfbadb&log=dmesg

MacBookPro9,2
https://bugzilla.kernel.org/attachment.cgi?id=278961

MacBookPro10,2
https://lkml.org/lkml/2014/9/22/657

MacBookPro11,2
https://forums.fedora-fr.org/viewtopic.php?id=70142

MacBookPro11,4
https://raw.githubusercontent.com/im-0/investigate-card-reader-suspend-problem-on-mbp11.4/master/test-16/dmesg

Fixes: 21245df307cb ("ACPI: video: Add Apple GMUX brightness control detection")
Link: https://lore.kernel.org/platform-driver-x86/20230123113750.462144-1-hdegoede@redhat.com/
Reported-by: Emmanouil Kouroupakis <kartebi@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230124105754.62167-3-hdegoede@redhat.com

1 files changed, 18 insertions, 52 deletions

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index a0af01f6a0fd..9333f82cfa8a 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -226,23 +226,6 @@ static void gmux_write32(struct apple_gmux_data *gmux_data, int port,
 		gmux_pio_write32(gmux_data, port, val);
 }
 
-static bool gmux_is_indexed(struct apple_gmux_data *gmux_data)
-{
-	u16 val;
-
-	outb(0xaa, gmux_data->iostart + 0xcc);
-	outb(0x55, gmux_data->iostart + 0xcd);
-	outb(0x00, gmux_data->iostart + 0xce);
-
-	val = inb(gmux_data->iostart + 0xcc) |
-		(inb(gmux_data->iostart + 0xcd) << 8);
-
-	if (val == 0x55aa)
-		return true;
-
-	return false;
-}
-
 /**
  * DOC: Backlight control
  *
@@ -582,60 +565,43 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 	int ret = -ENXIO;
 	acpi_status status;
 	unsigned long long gpe;
+	bool indexed = false;
+	u32 version;
 
 	if (apple_gmux_data)
 		return -EBUSY;
 
+	if (!apple_gmux_detect(pnp, &indexed)) {
+		pr_info("gmux device not present\n");
+		return -ENODEV;
+	}
+
 	gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
 	if (!gmux_data)
 		return -ENOMEM;
 	pnp_set_drvdata(pnp, gmux_data);
 
 	res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
-	if (!res) {
-		pr_err("Failed to find gmux I/O resource\n");
-		goto err_free;
-	}
-
 	gmux_data->iostart = res->start;
 	gmux_data->iolen = resource_size(res);
 
-	if (gmux_data->iolen < GMUX_MIN_IO_LEN) {
-		pr_err("gmux I/O region too small (%lu < %u)\n",
-		       gmux_data->iolen, GMUX_MIN_IO_LEN);
-		goto err_free;
-	}
-
 	if (!request_region(gmux_data->iostart, gmux_data->iolen,
 			    "Apple gmux")) {
 		pr_err("gmux I/O already in use\n");
 		goto err_free;
 	}
 
-	/*
-	 * Invalid version information may indicate either that the gmux
-	 * device isn't present or that it's a new one that uses indexed
-	 * io
-	 */
-
-	ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
-	ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
-	ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
-	if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
-		if (gmux_is_indexed(gmux_data)) {
-			u32 version;
-			mutex_init(&gmux_data->index_lock);
-			gmux_data->indexed = true;
-			version = gmux_read32(gmux_data,
-				GMUX_PORT_VERSION_MAJOR);
-			ver_major = (version >> 24) & 0xff;
-			ver_minor = (version >> 16) & 0xff;
-			ver_release = (version >> 8) & 0xff;
-		} else {
-			pr_info("gmux device not present\n");
-			ret = -ENODEV;
-			goto err_release;
-		}
+	if (indexed) {
+		mutex_init(&gmux_data->index_lock);
+		gmux_data->indexed = true;
+		version = gmux_read32(gmux_data, GMUX_PORT_VERSION_MAJOR);
+		ver_major = (version >> 24) & 0xff;
+		ver_minor = (version >> 16) & 0xff;
+		ver_release = (version >> 8) & 0xff;
+	} else {
+		ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
+		ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
+		ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
 	}
 	pr_info("Found gmux version %d.%d.%d [%s]\n", ver_major, ver_minor,
 		ver_release, (gmux_data->indexed ? "indexed" : "classic"));