pata_cs5536: add quirk for broken udma

I am working on a device which uses the cs5536 pata driver. There
are some broken hardware revisions out in the field, which can be
detected via DMI. On older versions with an embedded BIOS I
used libata.dma=0 to disable dma completely.
Now we are switching to a coreboot/seabios based BIOS where we
have DMI support and so I think its a good idea to get rid of
all those hacky kernel parameters as the same image
is used other devices where libata.dma=0 is not a good idea.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 31 insertions, 1 deletions

diff --git a/drivers/ata/pata_cs5536.c b/drivers/ata/pata_cs5536.c
index dec1b6c4b351..0448860a2077 100644
--- a/drivers/ata/pata_cs5536.c
+++ b/drivers/ata/pata_cs5536.c
@@ -38,6 +38,7 @@
 #include <linux/delay.h>
 #include <linux/libata.h>
 #include <scsi/scsi_host.h>
+#include <linux/dmi.h>
 
 #ifdef CONFIG_X86_32
 #include <asm/msr.h>
@@ -80,6 +81,21 @@ enum {
         IDE_ETC_UDMA_MASK       = 0xc0,
 };
 
+/* Some Bachmann OT200 devices have a non working UDMA support due a
+ * missing resistor.
+ */
+static const struct dmi_system_id udma_quirk_dmi_table[] = {
+        {
+                .ident = "Bachmann electronic OT200",
+                .matches = {
+                        DMI_MATCH(DMI_SYS_VENDOR, "Bachmann electronic"),
+                        DMI_MATCH(DMI_PRODUCT_NAME, "OT200"),
+                        DMI_MATCH(DMI_PRODUCT_VERSION, "1")
+                },
+        },
+        { }
+};
+
 static int cs5536_read(struct pci_dev *pdev, int reg, u32 *val)
 {
         if (unlikely(use_msr)) {
@@ -242,9 +258,23 @@ static int cs5536_init_one(struct pci_dev *dev, const struct pci_device_id *id)
                 .port_ops = &cs5536_port_ops,
         };
 
-        const struct ata_port_info *ppi[] = { &info, &ata_dummy_port_info };
+        static const struct ata_port_info no_udma_info = {
+                .flags = ATA_FLAG_SLAVE_POSS,
+                .pio_mask = ATA_PIO4,
+                .port_ops = &cs5536_port_ops,
+        };
+
+
+        const struct ata_port_info *ppi[2];
         u32 cfg;
 
+        if (dmi_check_system(udma_quirk_dmi_table))
+                ppi[0] = &no_udma_info;
+        else
+                ppi[0] = &info;
+
+        ppi[1] = &ata_dummy_port_info;
+
         if (use_msr)
                 printk(KERN_ERR DRV_NAME ": Using MSR regs instead of PCI\n");