From: Erik Jacobson <ejacobso@redhat.com>
Subject: [RHEL5 Patch] 1/2 BZ 221029 x86_64 big memory Intel S5000PAL systems freeze at startup
Date: Thu, 11 Jan 2007 20:08:28 -0500
Bugzilla: 221029
Message-Id: <20070112010828.GA14866@redhat.com>
Changelog: rng: check to see if bios locked device


Patch to see if the RNG device is locked by the BIOS.  If it is locked and the
OS driver attempts to configure/access it, memory corruption and/or system
hangs result.

commit 9863be598ed068613996af8da71d9fd976a0ab2d
Author: Jan Beulich <jbeulich@novell.com>

    [PATCH] intel-rng workarounds
    
    Add a load option to intel-rng to allow skipping the FWH detection,
    necessary in case the BIOS has locked read-only the firmware hub space.
    Also prevent any attempt to write to firmware space if it cannot be write
    enabled (apparently caused hangs on some systems not having an FWH and thus
    also not having a respective RNG).
    
    Signed-off-by: Jan Beulich <jbeulich@novell.com>
    Signed-off-by: Michael Buesch <mb@bu3sch.de>
    Cc: Jeff Garzik <jeff@garzik.org>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/char/hw_random/intel-rng.c b/drivers/char/hw_random/intel-rng.c
index 8efbc9c..154ce3e 100644
--- a/drivers/char/hw_random/intel-rng.c
+++ b/drivers/char/hw_random/intel-rng.c
@@ -143,6 +143,11 @@ static const struct pci_device_id pci_tb
 };
 MODULE_DEVICE_TABLE(pci, pci_tbl);
 
+static __initdata int no_fwh_detect;
+module_param(no_fwh_detect, int, 0);
+MODULE_PARM_DESC(no_fwh_detect, "Skip FWH detection:\n"
+                                " positive value - skip if FWH space locked read-only\n"
+                                " negative value - skip always");
 
 static inline u8 hwstatus_get(void __iomem *mem)
 {
@@ -240,6 +245,11 @@ static int __init mod_init(void)
 	if (!dev)
 		goto out; /* Device not found. */
 
+	if (no_fwh_detect < 0) {
+		pci_dev_put(dev);
+		goto fwh_done;
+	}
+
 	/* Check for Intel 82802 */
 	if (dev->device < 0x2640) {
 		fwh_dec_en1_off = FWH_DEC_EN1_REG_OLD;
@@ -252,6 +262,23 @@ static int __init mod_init(void)
 	pci_read_config_byte(dev, fwh_dec_en1_off, &fwh_dec_en1_val);
 	pci_read_config_byte(dev, bios_cntl_off, &bios_cntl_val);
 
+	if ((bios_cntl_val &
+	     (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK))
+	    == BIOS_CNTL_LOCK_ENABLE_MASK) {
+		static __initdata /*const*/ char warning[] =
+			KERN_WARNING PFX "Firmware space is locked read-only. If you can't or\n"
+			KERN_WARNING PFX "don't want to disable this in firmware setup, and if\n"
+			KERN_WARNING PFX "you are certain that your system has a functional\n"
+			KERN_WARNING PFX "RNG, try using the 'no_fwh_detect' option.\n";
+
+		pci_dev_put(dev);
+		if (no_fwh_detect)
+			goto fwh_done;
+		printk(warning);
+		err = -EBUSY;
+		goto out;
+	}
+
 	mem = ioremap_nocache(INTEL_FWH_ADDR, INTEL_FWH_ADDR_LEN);
 	if (mem == NULL) {
 		pci_dev_put(dev);
@@ -280,8 +307,7 @@ static int __init mod_init(void)
 		pci_write_config_byte(dev,
 		                      fwh_dec_en1_off,
 		                      fwh_dec_en1_val | FWH_F8_EN_MASK);
-	if (!(bios_cntl_val &
-	      (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK)))
+	if (!(bios_cntl_val & BIOS_CNTL_WRITE_ENABLE_MASK))
 		pci_write_config_byte(dev,
 		                      bios_cntl_off,
 		                      bios_cntl_val | BIOS_CNTL_WRITE_ENABLE_MASK);
@@ -315,6 +341,8 @@ static int __init mod_init(void)
 		goto out;
 	}
 
+fwh_done:
+
 	err = -ENOMEM;
 	mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
 	if (!mem)