[PATCH] ide: HPT3xx: fix PCI clock detection

Use the f_CNT value saved by the HighPoint BIOS if available as reading it
directly would give us a wrong PCI frequency after DPLL has already been
calibrated by BIOS.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 32 insertions, 14 deletions

diff --git a/drivers/ide/pci/hpt366.c b/drivers/ide/pci/hpt366.c
index 4968b16fa307..9fd50801d382 100644
--- a/drivers/ide/pci/hpt366.c
+++ b/drivers/ide/pci/hpt366.c
@@ -70,6 +70,8 @@
  * - fix/remove bad/unused timing tables and use one set of tables for the whole
  *   HPT37x chip family; save space by introducing the separate transfer mode
  *   table in which the mode lookup is done
+ * - use f_CNT value saved by  the HighPoint BIOS as reading it directly gives
+ *   the wrong PCI frequency since DPLL has already been calibrated by BIOS
  * - fix the hotswap code:  it caused RESET- to glitch when tristating the bus,
  *   and for HPT36x the obsolete HDIO_TRISTATE_HWIF handler was called instead
  * - pass to init_chipset() handlers a copy of the IDE PCI device structure as
@@ -1010,8 +1012,8 @@ static void __devinit hpt37x_clocking(ide_hwif_t *hwif)
         struct hpt_info *info = ide_get_hwifdata(hwif);
         struct pci_dev *dev = hwif->pci_dev;
         int adjust, i;
-        u16 freq;
-        u32 pll;
+        u16 freq = 0;
+        u32 pll, temp = 0;
         u8 reg5bh = 0, mcr1 = 0;
         
         /*
@@ -1025,15 +1027,34 @@ static void __devinit hpt37x_clocking(ide_hwif_t *hwif)
         pci_write_config_byte(dev, 0x5b, 0x23);
 
         /*
-         * set up the PLL. we need to adjust it so that it's stable. 
-         * freq = Tpll * 192 / Tpci
+         * We'll have to read f_CNT value in order to determine
+         * the PCI clock frequency according to the following ratio:
          *
-         * Todo. For non x86 should probably check the dword is
-         * set to 0xABCDExxx indicating the BIOS saved f_CNT
+         * f_CNT = Fpci * 192 / Fdpll
+         *
+         * First try reading the register in which the HighPoint BIOS
+         * saves f_CNT value before  reprogramming the DPLL from its
+         * default setting (which differs for the various chips).
+         * In case the signature check fails, we'll have to resort to
+         * reading the f_CNT register itself in hopes that nobody has
+         * touched the DPLL yet...
          */
-        pci_read_config_word(dev, 0x78, &freq);
-        freq &= 0x1FF;
-        
+        pci_read_config_dword(dev, 0x70, &temp);
+        if ((temp & 0xFFFFF000) != 0xABCDE000) {
+                int i;
+
+                printk(KERN_WARNING "HPT37X: no clock data saved by BIOS\n");
+
+                /* Calculate the average value of f_CNT */
+                for (temp = i = 0; i < 128; i++) {
+                        pci_read_config_word(dev, 0x78, &freq);
+                        temp += freq & 0x1ff;
+                        mdelay(1);
+                }
+                freq = temp / 128;
+        } else
+                freq = temp & 0x1ff;
+
         /*
          * HPT3xxN chips use different PCI clock information.
          * Currently we always set up the PLL for them.
@@ -1095,11 +1116,8 @@ static void __devinit hpt37x_clocking(ide_hwif_t *hwif)
         info->flags |= PLL_MODE;
         
         /*
-         * FIXME: make this work correctly, esp with 372N as per
-         * reference driver code.
-         *
-         * adjust PLL based upon PCI clock, enable it, and wait for
-         * stabilization.
+         * Adjust the PLL based upon the PCI clock, enable it, and
+         * wait for stabilization...
          */
         adjust = 0;
         freq = (pll < F_LOW_PCI_50) ? 2 : 4;