Hi Joseph,

> A bug was opened against the Ubuntu kernel[0].  It was found that 
> reverting the following commit resolved this bug:
> 
> commit 740fbddf5c3f9ad8b23c5d917ba1cc7e376a5104
> Author: Takahisa Tanaka <mc74h...@gmail.com>
> Date:   Sun Dec 2 14:33:18 2012 +0900
> 
>     watchdog: sp5100_tco: Add SB8x0 chipset support
> 
> 
> The regression was introduced as of v3.8-rc1.
> 
> I see that you are the author of this patch, so I wanted to run this by 
> you.  I was thinking of requesting a revert for v3.8, but I wanted to 
> get your feedback first.

Please check out the attached patches first (They are allready in linux-next).

Other references:
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43176
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43176

Kind regards,
Wim.

>From mc74h...@gmail.com Mon Jan 14 03:02:20 2013
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From: Takahisa Tanaka <mc74h...@gmail.com>
To: linux-watch...@vger.kernel.org
Cc: Wim Van Sebroeck <w...@iguana.be>,
        Paul Menzel <paulepan...@users.sourceforge.net>,
        Arkadiusz Miskiewicz <ar...@maven.pl>,
        Bjorn Helgaas <bhelg...@google.com>,
        Andrew Morton <a...@linux-foundation.org>,
        Jonathan Nieder <jrnie...@gmail.com>,
        linux-kernel@vger.kernel.org,
        Florian Mickler <flor...@mickler.org>,
        Takahisa Tanaka <mc74h...@gmail.com>
Subject: [PATCH 1/2] watchdog: sp5100_tco: Fix wrong indirect I/O access for 
getting value of reserved bits
Date: Mon, 14 Jan 2013 11:01:57 +0900
Message-Id: <1358128918-4415-1-git-send-email-mc74h...@gmail.com>
X-Mailer: git-send-email 1.7.11.7
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In case of SB800 or later chipset and re-programming MMIO address(*),
sp5100_tco module may read incorrect value of reserved bit, because the module
reads a value from an incorrect I/O address. However, this bug doesn't cause
a problem, because when re-programming MMIO address, by chance the module
writes zero (this is BIOS's default value) to the low three bits of register.
* In most cases, PC with SB8x0 or later chipset doesn't need to re-programming
  MMIO address, because such PC can enable AcpiMmio and can use 0xfed80b00 for
  watchdog register base address.

This patch fixes this bug.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43176
Signed-off-by: Takahisa Tanaka <mc74h...@gmail.com>
Signed-off-by: Wim Van Sebroeck <w...@iguana.be>
---
 drivers/watchdog/sp5100_tco.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
index 2b0e000..5dfe86e 100644
--- a/drivers/watchdog/sp5100_tco.c
+++ b/drivers/watchdog/sp5100_tco.c
@@ -500,14 +500,15 @@ static unsigned char sp5100_tco_setupdevice(void)
        /* Restore to the low three bits, if chipset is SB8x0(or later) */
        if (sp5100_tco_pci->revision >= 0x40) {
                u8 reserved_bit;
-               reserved_bit = inb(base_addr) & 0x7;
+               outb(base_addr+0, index_reg);
+               reserved_bit = inb(data_reg) & 0x7;
                val |= (u32)reserved_bit;
        }
 
        /* Re-programming the watchdog timer base address */
        outb(base_addr+0, index_reg);
        /* Low three bits of BASE are reserved */
-       outb((val >>  0) & 0xf8, data_reg);
+       outb((val >>  0) & 0xff, data_reg);
        outb(base_addr+1, index_reg);
        outb((val >>  8) & 0xff, data_reg);
        outb(base_addr+2, index_reg);
-- 
1.7.11.7


>From mc74h...@gmail.com Mon Jan 14 03:02:31 2013
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From: Takahisa Tanaka <mc74h...@gmail.com>
To: linux-watch...@vger.kernel.org
Cc: Wim Van Sebroeck <w...@iguana.be>,
        Paul Menzel <paulepan...@users.sourceforge.net>,
        Arkadiusz Miskiewicz <ar...@maven.pl>,
        Bjorn Helgaas <bhelg...@google.com>,
        Andrew Morton <a...@linux-foundation.org>,
        Jonathan Nieder <jrnie...@gmail.com>,
        linux-kernel@vger.kernel.org,
        Florian Mickler <flor...@mickler.org>,
        Takahisa Tanaka <mc74h...@gmail.com>
Subject: [PATCH 2/2] watchdog: sp5100_tco: Write back the original value to 
reserved bits, instead of zero
Date: Mon, 14 Jan 2013 11:01:58 +0900
Message-Id: <1358128918-4415-2-git-send-email-mc74h...@gmail.com>
X-Mailer: git-send-email 1.7.11.7
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Content-Length: 2279
Lines: 69

In case of SP5100 or SB7x0 chipsets, the sp5100_tco module writes zero to
reserved bits. The module, however, shouldn't depend on specific default
value, and should perform a read-merge-write operation for the reserved
bits.

This patch makes the sp5100_tco module perform a read-merge-write operation
on all the chipset (sp5100, sb7x0, sb8x0 or later).

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43176
Signed-off-by: Takahisa Tanaka <mc74h...@gmail.com>
Signed-off-by: Wim Van Sebroeck <w...@iguana.be>
---
 drivers/watchdog/sp5100_tco.c | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
index 5dfe86e..e3b8f75 100644
--- a/drivers/watchdog/sp5100_tco.c
+++ b/drivers/watchdog/sp5100_tco.c
@@ -361,7 +361,7 @@ static unsigned char sp5100_tco_setupdevice(void)
 {
        struct pci_dev *dev = NULL;
        const char *dev_name = NULL;
-       u32 val;
+       u32 val, tmp_val;
        u32 index_reg, data_reg, base_addr;
 
        /* Match the PCI device */
@@ -497,31 +497,19 @@ static unsigned char sp5100_tco_setupdevice(void)
                pr_debug("Got 0x%04x from resource tree\n", val);
        }
 
-       /* Restore to the low three bits, if chipset is SB8x0(or later) */
-       if (sp5100_tco_pci->revision >= 0x40) {
-               u8 reserved_bit;
-               outb(base_addr+0, index_reg);
-               reserved_bit = inb(data_reg) & 0x7;
-               val |= (u32)reserved_bit;
-       }
+       /* Restore to the low three bits */
+       outb(base_addr+0, index_reg);
+       tmp_val = val | (inb(data_reg) & 0x7);
 
        /* Re-programming the watchdog timer base address */
        outb(base_addr+0, index_reg);
-       /* Low three bits of BASE are reserved */
-       outb((val >>  0) & 0xff, data_reg);
+       outb((tmp_val >>  0) & 0xff, data_reg);
        outb(base_addr+1, index_reg);
-       outb((val >>  8) & 0xff, data_reg);
+       outb((tmp_val >>  8) & 0xff, data_reg);
        outb(base_addr+2, index_reg);
-       outb((val >> 16) & 0xff, data_reg);
+       outb((tmp_val >> 16) & 0xff, data_reg);
        outb(base_addr+3, index_reg);
-       outb((val >> 24) & 0xff, data_reg);
-
-       /*
-        * Clear unnecessary the low three bits,
-        * if chipset is SB8x0(or later)
-        */
-       if (sp5100_tco_pci->revision >= 0x40)
-               val &= ~0x7;
+       outb((tmp_val >> 24) & 0xff, data_reg);
 
        if (!request_mem_region_exclusive(val, SP5100_WDT_MEM_MAP_SIZE,
                                                                   dev_name)) {
-- 
1.7.11.7


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