[POWERPC] RTAS MSI implementation

Implement MSI support via RTAS (RTAS = run-time firmware on pSeries
machines).  For now we assumes that if the required RTAS tokens for
MSI are present, then we want to use the RTAS MSI routines.

When RTAS is managing MSIs for us, it will/may enable MSI on devices that
support it by default. This is contrary to the Linux model where a device
is in LSI mode until the driver requests MSIs.

To remedy this we add a pci_irq_fixup call, which disables MSI if they've
been assigned by firmware and the device also supports LSI. Devices that
don't support LSI at all will be left as is, drivers are still expected
to call pci_enable_msi() before using the device.

At the moment there is no pci_irq_fixup on pSeries, so we can just set it
unconditionally. If other platforms use the RTAS MSI backend they'll need
to check that still holds.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/pseries/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_SCANLOG)	+= scanlog.o
 obj-$(CONFIG_EEH)	+= eeh.o eeh_cache.o eeh_driver.o eeh_event.o
 obj-$(CONFIG_KEXEC)	+= kexec.o
 obj-$(CONFIG_PCI)	+= pci.o pci_dlpar.o
+obj-$(CONFIG_PCI_MSI)	+= msi.o
 
 obj-$(CONFIG_HOTPLUG_CPU)	+= hotplug-cpu.o
 

arch/powerpc/platforms/pseries/msi.c

+/*
+ * Copyright 2006 Jake Moilanen <moilanen@austin.ibm.com>, IBM Corp.
+ * Copyright 2006-2007 Michael Ellerman, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2 of the
+ * License.
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/irq.h>
+#include <linux/msi.h>
+
+#include <asm/rtas.h>
+#include <asm/hw_irq.h>
+#include <asm/ppc-pci.h>
+
+static int query_token, change_token;
+
+#define RTAS_QUERY_FN		0
+#define RTAS_CHANGE_FN		1
+#define RTAS_RESET_FN		2
+#define RTAS_CHANGE_MSI_FN	3
+#define RTAS_CHANGE_MSIX_FN	4
+
+static struct pci_dn *get_pdn(struct pci_dev *pdev)
+{
+	struct device_node *dn;
+	struct pci_dn *pdn;
+
+	dn = pci_device_to_OF_node(pdev);
+	if (!dn) {
+		dev_dbg(&pdev->dev, "rtas_msi: No OF device node\n");
+		return NULL;
+	}
+
+	pdn = PCI_DN(dn);
+	if (!pdn) {
+		dev_dbg(&pdev->dev, "rtas_msi: No PCI DN\n");
+		return NULL;
+	}
+
+	return pdn;
+}
+
+/* RTAS Helpers */
+
+static int rtas_change_msi(struct pci_dn *pdn, u32 func, u32 num_irqs)
+{
+	u32 addr, seq_num, rtas_ret[3];
+	unsigned long buid;
+	int rc;
+
+	addr = rtas_config_addr(pdn->busno, pdn->devfn, 0);
+	buid = pdn->phb->buid;
+
+	seq_num = 1;
+	do {
+		if (func == RTAS_CHANGE_MSI_FN || func == RTAS_CHANGE_MSIX_FN)
+			rc = rtas_call(change_token, 6, 4, rtas_ret, addr,
+					BUID_HI(buid), BUID_LO(buid),
+					func, num_irqs, seq_num);
+		else
+			rc = rtas_call(change_token, 6, 3, rtas_ret, addr,
+					BUID_HI(buid), BUID_LO(buid),
+					func, num_irqs, seq_num);
+
+		seq_num = rtas_ret[1];
+	} while (rtas_busy_delay(rc));
+
+	if (rc == 0) /* Success */
+		rc = rtas_ret[0];
+
+	pr_debug("rtas_msi: ibm,change_msi(func=%d,num=%d) = (%d)\n",
+		 func, num_irqs, rc);
+
+	return rc;
+}
+
+static void rtas_disable_msi(struct pci_dev *pdev)
+{
+	struct pci_dn *pdn;
+
+	pdn = get_pdn(pdev);
+	if (!pdn)
+		return;
+
+	if (rtas_change_msi(pdn, RTAS_CHANGE_FN, 0) != 0)
+		pr_debug("rtas_msi: Setting MSIs to 0 failed!\n");
+}
+
+static int rtas_query_irq_number(struct pci_dn *pdn, int offset)
+{
+	u32 addr, rtas_ret[2];
+	unsigned long buid;
+	int rc;
+
+	addr = rtas_config_addr(pdn->busno, pdn->devfn, 0);
+	buid = pdn->phb->buid;
+
+	do {
+		rc = rtas_call(query_token, 4, 3, rtas_ret, addr,
+			       BUID_HI(buid), BUID_LO(buid), offset);
+	} while (rtas_busy_delay(rc));
+
+	if (rc) {
+		pr_debug("rtas_msi: error (%d) querying source number\n", rc);
+		return rc;
+	}
+
+	return rtas_ret[0];
+}
+
+static void rtas_teardown_msi_irqs(struct pci_dev *pdev)
+{
+	struct msi_desc *entry;
+
+	list_for_each_entry(entry, &pdev->msi_list, list) {
+		if (entry->irq == NO_IRQ)
+			continue;
+
+		set_irq_msi(entry->irq, NULL);
+		irq_dispose_mapping(entry->irq);
+	}
+
+	rtas_disable_msi(pdev);
+}
+
+static int check_req_msi(struct pci_dev *pdev, int nvec)
+{
+	struct device_node *dn;
+	struct pci_dn *pdn;
+	const u32 *req_msi;
+
+	pdn = get_pdn(pdev);
+	if (!pdn)
+		return -ENODEV;
+
+	dn = pdn->node;
+
+	req_msi = of_get_property(dn, "ibm,req#msi", NULL);
+	if (!req_msi) {
+		pr_debug("rtas_msi: No ibm,req#msi on %s\n", dn->full_name);
+		return -ENOENT;
+	}
+
+	if (*req_msi < nvec) {
+		pr_debug("rtas_msi: ibm,req#msi requests < %d MSIs\n", nvec);
+		return -ENOSPC;
+	}
+
+	return 0;
+}
+
+static int rtas_msi_check_device(struct pci_dev *pdev, int nvec, int type)
+{
+	if (type == PCI_CAP_ID_MSIX)
+		pr_debug("rtas_msi: MSI-X untested, trying anyway.\n");
+
+	return check_req_msi(pdev, nvec);
+}
+
+static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
+{
+	struct pci_dn *pdn;
+	int hwirq, virq, i, rc;
+	struct msi_desc *entry;
+
+	pdn = get_pdn(pdev);
+	if (!pdn)
+		return -ENODEV;
+
+	/*
+	 * Try the new more explicit firmware interface, if that fails fall
+	 * back to the old interface. The old interface is known to never
+	 * return MSI-Xs.
+	 */
+	if (type == PCI_CAP_ID_MSI) {
+		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSI_FN, nvec);
+
+		if (rc != nvec) {
+			pr_debug("rtas_msi: trying the old firmware call.\n");
+			rc = rtas_change_msi(pdn, RTAS_CHANGE_FN, nvec);
+		}
+	} else
+		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSIX_FN, nvec);
+
+	if (rc != nvec) {
+		pr_debug("rtas_msi: rtas_change_msi() failed\n");
+
+		/*
+		 * In case of an error it's not clear whether the device is
+		 * left with MSI enabled or not, so we explicitly disable.
+		 */
+		goto out_free;
+	}
+
+	i = 0;
+	list_for_each_entry(entry, &pdev->msi_list, list) {
+		hwirq = rtas_query_irq_number(pdn, i);
+		if (hwirq < 0) {
+			rc = hwirq;
+			pr_debug("rtas_msi: error (%d) getting hwirq\n", rc);
+			goto out_free;
+		}
+
+		virq = irq_create_mapping(NULL, hwirq);
+
+		if (virq == NO_IRQ) {
+			pr_debug("rtas_msi: Failed mapping hwirq %d\n", hwirq);
+			rc = -ENOSPC;
+			goto out_free;
+		}
+
+		dev_dbg(&pdev->dev, "rtas_msi: allocated virq %d\n", virq);
+		set_irq_msi(virq, entry);
+		unmask_msi_irq(virq);
+	}
+
+	return 0;
+
+ out_free:
+	rtas_teardown_msi_irqs(pdev);
+	return rc;
+}
+
+static void rtas_msi_pci_irq_fixup(struct pci_dev *pdev)
+{
+	/* No LSI -> leave MSIs (if any) configured */
+	if (pdev->irq == NO_IRQ) {
+		dev_dbg(&pdev->dev, "rtas_msi: no LSI, nothing to do.\n");
+		return;
+	}
+
+	/* No MSI -> MSIs can't have been assigned by fw, leave LSI */
+	if (check_req_msi(pdev, 1)) {
+		dev_dbg(&pdev->dev, "rtas_msi: no req#msi, nothing to do.\n");
+		return;
+	}
+
+	dev_dbg(&pdev->dev, "rtas_msi: disabling existing MSI.\n");
+	rtas_disable_msi(pdev);
+}
+
+static int rtas_msi_init(void)
+{
+	query_token  = rtas_token("ibm,query-interrupt-source-number");
+	change_token = rtas_token("ibm,change-msi");
+
+	if ((query_token == RTAS_UNKNOWN_SERVICE) ||
+			(change_token == RTAS_UNKNOWN_SERVICE)) {
+		pr_debug("rtas_msi: no RTAS tokens, no MSI support.\n");
+		return -1;
+	}
+
+	pr_debug("rtas_msi: Registering RTAS MSI callbacks.\n");
+
+	WARN_ON(ppc_md.setup_msi_irqs);
+	ppc_md.setup_msi_irqs = rtas_setup_msi_irqs;
+	ppc_md.teardown_msi_irqs = rtas_teardown_msi_irqs;
+	ppc_md.msi_check_device = rtas_msi_check_device;
+
+	WARN_ON(ppc_md.pci_irq_fixup);
+	ppc_md.pci_irq_fixup = rtas_msi_pci_irq_fixup;
+
+	return 0;
+}
+arch_initcall(rtas_msi_init);