[PATCH v2] ns16550: enable memory decoding on MMIO-based PCI console card

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

pci_serial_early_init() enables PCI_COMMAND_IO for IO-based UART
devices, add setting PCI_COMMAND_MEMORY for MMIO-based UART devices too.
Note the MMIO-based devices in practice need a "pci" sub-option,
otherwise a few parameters are not initialized (including bar_idx,
reg_shift, reg_width etc). The "pci" is not supposed to be used with
explicit BDF, so do not key setting PCI_COMMAND_MEMORY on explicit BDF
being set. Contrary to the IO-based UART, pci_serial_early_init() will
not attempt to set BAR0 address, even if user provided io_base manually
- in most cases, those are with an offest and the current cmdline syntax
doesn't allow expressing it. Due to this, enable PCI_COMMAND_MEMORY only
if uart->bar is already populated. In similar spirit, this patch does
not support setting BAR0 of the bridge.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
This fixes the issue I was talking about on #xendevel. Thanks Roger for
the hint.

Changes in v2:
 - check if uart->bar instead of uart->io_base
 - move it ahead of !uart->ps_bdf_enable return
 - expand commit message.
---
 xen/drivers/char/ns16550.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 1b21eb93c45f..34231dcb23ea 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -272,7 +272,15 @@ static int cf_check ns16550_getc(struct serial_port *port, 
char *pc)
 static void pci_serial_early_init(struct ns16550 *uart)
 {
 #ifdef NS16550_PCI
-    if ( !uart->ps_bdf_enable || uart->io_base >= 0x10000 )
+    if ( uart->bar )
+    {
+        pci_conf_write16(PCI_SBDF(0, uart->ps_bdf[0], uart->ps_bdf[1],
+                                  uart->ps_bdf[2]),
+                         PCI_COMMAND, PCI_COMMAND_MEMORY);
+        return;
+    }
+
+    if ( !uart->ps_bdf_enable )
         return;
 
     if ( uart->pb_bdf_enable )
-- 
2.39.2