[SeaBIOS] [RFC] [PATCH 1/2] Implement support for transitioning from 16 bit to 32 bit

[Kevin O'Connor]

On Tue, Nov 23, 2010 at 11:32:13AM +0100, Gerd Hoffmann wrote:
> On 11/23/10 02:13, Kevin O'Connor wrote:
> >On Mon, Nov 22, 2010 at 07:40:36PM -0500, Kevin O'Connor wrote:
> >>It should be possible to extend call32() to do what you need -
> >
> >FYI - here's what call32 extended to pass a parameter looks like:
> >
> >--- a/src/stacks.c
> >+++ b/src/stacks.c
> >@@ -37,14 +37,14 @@ static inline void lgdt(struct descloc_s *desc) {
> >  }
> >
> >  // Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
> >-static inline int
> >-call32(void *func)
> >+static inline u32
> >+call32(void *func, u32 eax, u32 errret)
> 
> Tried to use that (see patch).  Failed.  When calling pci_readl from
> real mode I see the pci_readl debug printf but not the one from
> pci_readl_32 ...

You need to make sure the 32bit function is only available in 32bit
mode.  See below.

I briefly tested this and the call completes, but it caused issues
with bootup - I'm not sure if this is due to a bug somewhere or due to
32bit mode switching being inherently unsafe.

-Kevin


--- a/src/stacks.c
+++ b/src/stacks.c
@@ -395,3 +395,28 @@ check_preempt(void)
 
     call32(yield_preempt, 0, 0);
 }
+
+extern u32 pci_readl_32(u32 addr);
+#if MODESEGMENT == 0
+u32 VISIBLE32FLAT
+pci_readl_32(u32 addr)
+{
+    dprintf(1, "pci rd32: %x\n", addr);
+    return readl((void*)addr);
+}
+#endif
+
+u32 pci_readl(u32 addr)
+{
+    dprintf(1, "pci read: %x\n", addr);
+    if (MODESEGMENT)
+        return call32(pci_readl_32, addr, -1);
+    return pci_readl_32(addr);
+}
+
+void pci_writel(u32 addr, u32 val)
+{
+    dprintf(1, "pci write: %x, %x\n", addr, val);
+    if (!MODESEGMENT)
+        writel((void*)addr, val);
+}