[PATCH v2] acpi: reboot: log reset parameters

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx> 

Xen does not provide much details for system reset debugging in case
system reset happens via ACPI subsystem.

Log reset I/O address and reset value.

While here, add the missing default case, add breaks between case
statements and drop full stops in the loglines.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
- v1: 
https://lore.kernel.org/xen-devel/20260730001854.905354-2-dmukhin@xxxxxxxx/ 
- CI: https://gitlab.com/xen-project/people/dmukhin/xen/-/pipelines/2723268852

Changes since v1:
- removed wrong ASSERT_UNREACHABLE()
- switched formatting to %#x
- fixed indentation
---
 xen/drivers/acpi/reboot.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/xen/drivers/acpi/reboot.c b/xen/drivers/acpi/reboot.c
index f6345be8749f..dc5671f9b42a 100644
--- a/xen/drivers/acpi/reboot.c
+++ b/xen/drivers/acpi/reboot.c
@@ -6,6 +6,7 @@ void acpi_reboot(void)
 {
        struct acpi_generic_address *rr;
        u8 reset_value;
+       pci_sbdf_t sbdf;
 
        rr = &acpi_gbl_FADT.reset_register;
 
@@ -21,17 +22,30 @@ void acpi_reboot(void)
         * on a device on bus 0. */
        switch (rr->space_id) {
        case ACPI_ADR_SPACE_PCI_CONFIG:
-               printk("Resetting with ACPI PCI RESET_REG.\n");
+               sbdf = PCI_SBDF(0, 0, rr->address >> 32, rr->address >> 16);
+               printk("Resetting with ACPI PCI %pp RESET_REG at %#lx (%#x)\n",
+                      &sbdf, rr->address & 0xff, reset_value);
                /* Write the value that resets us. */
-               pci_conf_write8(PCI_SBDF(0, 0, rr->address >> 32,
-                                        rr->address >> 16),
-                               (rr->address & 255),
-                               reset_value);
+               pci_conf_write8(sbdf, rr->address & 0xff, reset_value);
                break;
+
        case ACPI_ADR_SPACE_SYSTEM_MEMORY:
-       case ACPI_ADR_SPACE_SYSTEM_IO:
-               printk("Resetting with ACPI MEMORY or I/O RESET_REG.\n");
+               printk("Resetting with ACPI MEMORY at %#lx (%#x)\n",
+                      rr->address, reset_value);
                acpi_hw_low_level_write(8, reset_value, rr);
                break;
+
+       case ACPI_ADR_SPACE_SYSTEM_IO:
+               printk("Resetting with I/O RESET_REG at %#lx (%#x)\n",
+                      rr->address, reset_value);
+               acpi_hw_low_level_write(8, reset_value, rr);
+               break;
+
+       default:
+               /* Fallback to alternative reboot methods */
+               printk(XENLOG_WARNING
+                      "Resetting with ACPI method failed: bad ADR %#x\n",
+                      rr->space_id);
+               break;
        }
 }
-- 
2.54.0