[xen stable-4.16] ns16550: enable memory decoding on MMIO-based PCI console card

[patchbot@xxxxxxx]

commit dbd05c62edd304c9bf0dfd8698bdcf0fa71b5b26
Author:     Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Tue May 23 15:02:09 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 23 15:02:09 2023 +0200

    ns16550: enable memory decoding on MMIO-based PCI console card
    
    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>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: a16fb78515d54be95f81c0d1c0a3a7b954a54d0a
    master date: 2023-05-08 14:15:38 +0200
---
 xen/drivers/char/ns16550.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 3651e0c0d4..08c654e901 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -271,6 +271,14 @@ static int ns16550_getc(struct serial_port *port, char *pc)
 static void pci_serial_early_init(struct ns16550 *uart)
 {
 #ifdef NS16550_PCI
+    if ( uart->bar && uart->io_base >= 0x10000 )
+    {
+        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 || uart->io_base >= 0x10000 )
         return;
 
--
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