TEMP: iommu/omap: add support for performing a "late attach"

The remoteproc module has a concept of "late attach" whereby a remote
core is loaded externally to remoteproc, for which remoteproc must
attach to the core without disrupting its existing state. Introduce an
iommu-based "late attach" model for the same use case.

In the "late attach" model, the iommu subsystem is mostly unused since
the external loader will have programmed the remote core's mmu, but
certain "attach" functionality must be performed so that subsequent
"detach" functionality can complete.

This logic is detected in the driver through a "ti,late-attach" property
set on the IOMMU node in the device tree. The IOMMU node should also have
the "ti,no-init-on-reset" and "ti,no-init-on-idle" so that the omap_hwmod
and omap_device layers do not reset and idle/disable the device during
the initial kernel boot. This "ti,late-attach" is therefore removed from
the device tree on the first probe so that further probes or remoteproc
recovery boots treat the IOMMU device normally.

Signed-off-by: Venkateswara Rao Mandela <venkat.mandela@ti.com>
Signed-off-by: Angela Stegmaier <angelabaker@ti.com>
Signed-off-by: Subash Lakkimsetti <x0091084@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Shravan Karthik <shravan.karthik@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>

drivers/iommu/omap-iommu-debug.c

@@ -197,7 +197,7 @@ static void dump_ioptable(struct seq_file *s)
 			continue;
 		}
 
-		iopte = iopte_offset(iopgd, 0);
+		iopte = iopte_get(obj, iopgd, 0);
 		for (j = 0; j < PTRS_PER_IOPTE; j++, iopte++) {
 			if (!*iopte)
 				continue;

drivers/iommu/omap-iommu.c

@@ -44,6 +44,12 @@ static const struct iommu_ops omap_iommu_ops;
 /* bitmap of the page sizes currently supported */
 #define OMAP_IOMMU_PGSIZES	(SZ_4K | SZ_64K | SZ_1M | SZ_16M)
 
+/*
+ * total size of L1 and L2 page tables reserved/used by bootloader per rproc
+ * for early boot usecases, must match the value used in bootloader
+ */
+#define EARLY_PAGE_TABLES_SIZE	SZ_256K
+
 #define MMU_LOCK_BASE_SHIFT	10
 #define MMU_LOCK_BASE_MASK	(0x1f << MMU_LOCK_BASE_SHIFT)
 #define MMU_LOCK_BASE(x)	\
@@ -163,7 +169,7 @@ static int omap2_iommu_enable(struct omap_iommu *obj)
 	if (!obj->iopgd || !IS_ALIGNED((u32)obj->iopgd,  SZ_16K))
 		return -EINVAL;
 
-	pa = virt_to_phys(obj->iopgd);
+	pa = obj->iopgd_pa;
 	if (!IS_ALIGNED(pa, SZ_16K))
 		return -EINVAL;
 
@@ -198,6 +204,15 @@ static int iommu_enable(struct omap_iommu *obj)
 {
 	int ret;
 
+	/*
+	 * now that the threat of idling has passed, decrement the
+	 * device usage count to balance the increment done in probe,
+	 * the pm runtime device usage count will be managed normally
+	 * from here on
+	 */
+	if (obj->late_attach)
+		pm_runtime_put_noidle(obj->dev);
+
 	ret = pm_runtime_get_sync(obj->dev);
 	if (ret < 0)
 		pm_runtime_put_noidle(obj->dev);
@@ -537,7 +552,7 @@ static u32 *iopte_alloc(struct omap_iommu *obj, u32 *iopgd,
 	}
 
 pte_ready:
-	iopte = iopte_offset(iopgd, da);
+	iopte = iopte_get(obj, iopgd, da);
 	*pt_dma = iopgd_page_paddr(iopgd);
 	dev_vdbg(obj->dev,
 		 "%s: da:%08x pgd:%p *pgd:%08x pte:%p *pte:%08x\n",
@@ -696,7 +711,7 @@ iopgtable_lookup_entry(struct omap_iommu *obj, u32 da, u32 **ppgd, u32 **ppte)
 		goto out;
 
 	if (iopgd_is_table(*iopgd))
-		iopte = iopte_offset(iopgd, da);
+		iopte = iopte_get(obj, iopgd, da);
 out:
 	*ppgd = iopgd;
 	*ppte = iopte;
@@ -716,13 +731,13 @@ static size_t iopgtable_clear_entry_core(struct omap_iommu *obj, u32 da)
 
 	if (iopgd_is_table(*iopgd)) {
 		int i;
-		u32 *iopte = iopte_offset(iopgd, da);
+		u32 *iopte = iopte_get(obj, iopgd, da);
 
 		bytes = IOPTE_SIZE;
 		if (*iopte & IOPTE_LARGE) {
 			nent *= 16;
 			/* rewind to the 1st entry */
-			iopte = iopte_offset(iopgd, (da & IOLARGE_MASK));
+			iopte = iopte_get(obj, iopgd, (da & IOLARGE_MASK));
 		}
 		bytes *= nent;
 		memset(iopte, 0, nent * sizeof(*iopte));
@@ -732,7 +747,8 @@ static size_t iopgtable_clear_entry_core(struct omap_iommu *obj, u32 da)
 		/*
 		 * do table walk to check if this table is necessary or not
 		 */
-		iopte = iopte_offset(iopgd, 0);
+		iopte = iopte_get(obj, iopgd, 0);
+
 		for (i = 0; i < PTRS_PER_IOPTE; i++)
 			if (iopte[i])
 				goto out;
@@ -791,8 +807,15 @@ static void iopgtable_clear_entry_all(struct omap_iommu *obj)
 		if (!*iopgd)
 			continue;
 
-		if (iopgd_is_table(*iopgd))
-			iopte_free(obj, iopte_offset(iopgd, 0), true);
+		if (iopgd_is_table(*iopgd)) {
+			if (obj->late_attach)
+				iopte_free(obj, iopte_offset_lateattach(obj,
+									iopgd,
+									0),
+					   true);
+			else
+				iopte_free(obj, iopte_offset(iopgd, 0), true);
+		}
 
 		*iopgd = 0;
 		flush_iopte_range(obj->dev, obj->pd_dma, offset, 1);
@@ -835,7 +858,7 @@ static irqreturn_t iommu_fault_handler(int irq, void *data)
 		return IRQ_NONE;
 	}
 
-	iopte = iopte_offset(iopgd, da);
+	iopte = iopte_get(obj, iopgd, da);
 
 	dev_err(obj->dev, "%s: errs:0x%08x da:0x%08x pgd:0x%p *pgd:0x%08x pte:0x%p *pte:0x%08x\n",
 		obj->name, errs, da, iopgd, *iopgd, iopte, *iopte);
@@ -851,6 +874,16 @@ static irqreturn_t iommu_fault_handler(int irq, void *data)
 static int omap_iommu_attach(struct omap_iommu *obj, u32 *iopgd)
 {
 	int err;
+	u32 iopgd_pa;
+
+	if (obj->late_attach) {
+		iopgd_pa = iommu_read_reg(obj, MMU_TTB);
+		iopgd = ioremap(iopgd_pa, EARLY_PAGE_TABLES_SIZE);
+		if (!iopgd)
+			return -ENOMEM;
+	} else {
+		iopgd_pa = virt_to_phys(iopgd);
+	}
 
 	spin_lock(&obj->iommu_lock);
 
@@ -862,11 +895,14 @@ static int omap_iommu_attach(struct omap_iommu *obj, u32 *iopgd)
 		goto out_err;
 	}
 
+	obj->iopgd_pa = iopgd_pa;
 	obj->iopgd = iopgd;
 	err = iommu_enable(obj);
 	if (err)
 		goto out_err;
-	flush_iotlb_all(obj);
+
+	if (!obj->late_attach)
+		flush_iotlb_all(obj);
 
 	spin_unlock(&obj->iommu_lock);
 
@@ -889,13 +925,19 @@ static void omap_iommu_detach(struct omap_iommu *obj)
 	if (!obj || IS_ERR(obj))
 		return;
 
+	if (obj->late_attach && obj->iopgd)
+		iounmap(obj->iopgd);
+
 	spin_lock(&obj->iommu_lock);
 
 	dma_unmap_single(obj->dev, obj->pd_dma, IOPGD_TABLE_SIZE,
 			 DMA_TO_DEVICE);
 	obj->pd_dma = 0;
+
+	obj->iopgd_pa = 0;
 	obj->iopgd = NULL;
 	iommu_disable(obj);
+	obj->late_attach = 0;
 
 	spin_unlock(&obj->iommu_lock);
 
@@ -1069,7 +1111,9 @@ static int omap_iommu_runtime_resume(struct device *dev)
 		}
 	}
 
-	if (pdata && pdata->deassert_reset) {
+	/* do not deassert reset only during initial boot for late attach */
+	if ((!obj->late_attach || obj->domain) &&
+	    pdata && pdata->deassert_reset) {
 		ret = pdata->deassert_reset(pdev, pdata->reset_name);
 		if (ret) {
 			dev_err(dev, "deassert_reset failed: %d\n", ret);
@@ -1170,6 +1214,7 @@ static int omap_iommu_probe(struct platform_device *pdev)
 	struct omap_iommu *obj;
 	struct resource *res;
 	struct device_node *of = pdev->dev.of_node;
+	struct iommu_platform_data *pdata = dev_get_platdata(&pdev->dev);
 
 	if (!of) {
 		pr_err("%s: only DT-based devices are supported\n", __func__);
@@ -1192,6 +1237,7 @@ static int omap_iommu_probe(struct platform_device *pdev)
 	obj->name = dev_name(&pdev->dev);
 	obj->nr_tlb_entries = 32;
 	err = of_property_read_u32(of, "ti,#tlb-entries", &obj->nr_tlb_entries);
+
 	if (err && err != -EINVAL)
 		return err;
 	if (obj->nr_tlb_entries != 32 && obj->nr_tlb_entries != 8)
@@ -1199,6 +1245,10 @@ static int omap_iommu_probe(struct platform_device *pdev)
 	if (of_find_property(of, "ti,iommu-bus-err-back", NULL))
 		obj->has_bus_err_back = MMU_GP_REG_BUS_ERR_BACK_EN;
 
+	if (pdata && pdata->device_is_enabled &&
+	    pdata->device_is_enabled(pdev))
+		obj->late_attach = 1;
+
 	obj->dev = &pdev->dev;
 	obj->ctx = (void *)obj + sizeof(*obj);
 	obj->cr_ctx = devm_kzalloc(&pdev->dev,
@@ -1247,6 +1297,15 @@ static int omap_iommu_probe(struct platform_device *pdev)
 	}
 
 	pm_runtime_irq_safe(obj->dev);
+
+	/*
+	 * increment the device usage count so that runtime_suspend is not
+	 * invoked immediately after the probe (due to the ti,no-idle-on-init)
+	 * and before any remoteproc has attached to the iommu
+	 */
+	if (obj->late_attach)
+		pm_runtime_get_noresume(obj->dev);
+
 	pm_runtime_enable(obj->dev);
 
 	omap_iommu_debugfs_add(obj);
@@ -1428,6 +1487,11 @@ static int omap_iommu_attach_init(struct device *dev,
 
 	iommu = odomain->iommus;
 	for (i = 0; i < odomain->num_iommus; i++, iommu++) {
+		/*
+		 * not necessary for late attach, the page table would be setup
+		 * by the boot loader. Leaving the below code in place, it does
+		 * not have any side effects during late attach.
+		 */
 		iommu->pgtable = kzalloc(IOPGD_TABLE_SIZE, GFP_ATOMIC);
 		if (!iommu->pgtable)
 			return -ENOMEM;
@@ -1549,7 +1613,8 @@ static void _omap_iommu_detach_dev(struct omap_iommu_domain *omap_domain,
 	arch_data += (omap_domain->num_iommus - 1);
 	for (i = 0; i < omap_domain->num_iommus; i++, iommu--, arch_data--) {
 		oiommu = iommu->iommu_dev;
-		iopgtable_clear_entry_all(oiommu);
+		if (!oiommu->late_attach)
+			iopgtable_clear_entry_all(oiommu);
 
 		omap_iommu_detach(oiommu);
 		iommu->iommu_dev = NULL;

drivers/iommu/omap-iommu.h

@@ -69,6 +69,8 @@ struct omap_iommu {
 	 * but share it globally for each iommu.
 	 */
 	u32		*iopgd;
+	u32		iopgd_pa;
+	u32		late_attach;
 	spinlock_t	page_table_lock; /* protect iopgd */
 	dma_addr_t	pd_dma;
 
@@ -272,4 +274,12 @@ static inline int iotlb_cr_valid(struct cr_regs *cr)
 	return cr->cam & MMU_CAM_V;
 }
 
+static inline u32 *iopte_get(struct omap_iommu *obj, u32 *iopgd, u32 da)
+{
+	if (obj->late_attach)
+		return iopte_offset_lateattach(obj, iopgd, da);
+	else
+		return iopte_offset(iopgd, da);
+}
+
 #endif /* _OMAP_IOMMU_H */

drivers/iommu/omap-iopgtable.h

@@ -99,4 +99,16 @@ static inline phys_addr_t omap_iommu_translate(u32 d, u32 va, u32 mask)
 #define iopte_index(da)		(((da) >> IOPTE_SHIFT) & (PTRS_PER_IOPTE - 1))
 #define iopte_offset(iopgd, da)	(iopgd_page_vaddr(iopgd) + iopte_index(da))
 
+/*
+ * compute vaddr for second-level page table relative to page table directory
+ * for late-attach mode
+ */
+#define iopgd_page_vaddr_lateattach(obj, pgd)				\
+	((u32 *)((u32 *)((obj)->iopgd)) +				\
+	((u32 *)iopgd_page_paddr((pgd)) - (u32 *)((obj)->iopgd_pa)))
+
+/* to find an entry in the second-level page table for late-attach mode */
+#define iopte_offset_lateattach(obj, iopgd, da)				\
+	(iopgd_page_vaddr_lateattach(obj, iopgd) + iopte_index(da))
+
 #endif /* _OMAP_IOPGTABLE_H */