s390/pci: add parameter to disable usage of MIO instructions

Allow users to disable usage of MIO instructions by specifying pci=nomio
at the kernel command line.

Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index abc1b6e305c4a3aafff13ea9ae42ff4a9dbe9cdc..055284c31e3707b1a8728f75091b36f5a1688a4a 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3395,6 +3395,7 @@
                                this removes isolation between devices and
                                may put more devices in an IOMMU group.
                force_floating  [S390] Force usage of floating interrupts.
+               nomio           [S390] Do not use MIO instructions.
 
        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                        Management.

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index dff8f4526c8dbe63b8101929e0776d338ccd1d4b..0ebb7c405a2508d28c66530eaf1b39b4598635b5 100644 (file)
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -850,6 +850,7 @@ static void zpci_mem_exit(void)
 }
 
 static unsigned int s390_pci_probe __initdata = 1;
+static unsigned int s390_pci_no_mio __initdata;
 unsigned int s390_pci_force_floating __initdata;
 static unsigned int s390_pci_initialized;
 
@@ -859,6 +860,10 @@ char * __init pcibios_setup(char *str)
                s390_pci_probe = 0;
                return NULL;
        }
+       if (!strcmp(str, "nomio")) {
+               s390_pci_no_mio = 1;
+               return NULL;
+       }
        if (!strcmp(str, "force_floating")) {
                s390_pci_force_floating = 1;
                return NULL;
@@ -881,7 +886,7 @@ static int __init pci_base_init(void)
        if (!test_facility(69) || !test_facility(71))
                return 0;
 
-       if (test_facility(153))
+       if (test_facility(153) && !s390_pci_no_mio)
                static_branch_enable(&have_mio);
 
        rc = zpci_debug_init();