Subject: Re: [PATCH kernel v10 15/34] powerpc/powernv/ioda/ioda2: Rework TCE invalidation in tce_build()/tce_free()

From: Gavin Shan <[email-masked]>
Date: Thu, 14 May 2015 10:48:25 +1000

On Tue, May 12, 2015 at 01:39:04AM +1000, Alexey Kardashevskiy wrote:
>The pnv_pci_ioda_tce_invalidate() helper invalidates TCE cache. It is
>supposed to be called on IODA1/2 and not called on p5ioc2. It receives
>start and end host addresses of TCE table.
>
>IODA2 actually needs PCI addresses to invalidate the cache. Those
>can be calculated from host addresses but since we are going
>to implement multi-level TCE tables, calculating PCI address from
>a host address might get either tricky or ugly as TCE table remains flat
>on PCI bus but not in RAM.
>
>This moves pnv_pci_ioda_tce_invalidate() from generic pnv_tce_build/
>pnt_tce_free and defines IODA1/2-specific callbacks which call generic
>ones and do PHB-model-specific TCE cache invalidation. P5IOC2 keeps
>using generic callbacks as before.
>
>This changes pnv_pci_ioda2_tce_invalidate() to receives TCE index and
>number of pages which are PCI addresses shifted by IOMMU page shift.
>
>No change in behaviour is expected.
>
>Signed-off-by: Alexey Kardashevskiy <[email-masked]>
>Reviewed-by: David Gibson <[email-masked]>

Reviewed-by: Gavin Shan <[email-masked]>

>---
>Changes:
>v10:
>* moved before "Switch from iommu_table to new iommu_table_group" as it adds
>list of groups to iommu_table and tce invalidation depends on it
>
>v9:
>* removed confusing comment from commit log about unintentional calling of
>pnv_pci_ioda_tce_invalidate()
>* moved mechanical changes away to "powerpc/iommu: Move tce_xxx callbacks from ppc_md to iommu_table"
>* fixed bug with broken invalidation in pnv_pci_ioda2_tce_invalidate -
>@index includes @tbl->it_offset but old code added it anyway which later broke
>DDW
>---
> arch/powerpc/platforms/powernv/pci-ioda.c | 81 ++++++++++++++++++++++---------
> arch/powerpc/platforms/powernv/pci.c      | 17 ++-----
> 2 files changed, 61 insertions(+), 37 deletions(-)
>
>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>index 2924abe..1b43e25 100644
>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>@@ -1678,18 +1678,19 @@ static void pnv_ioda_setup_bus_dma(struct pnv_ioda_pe *pe,
> 	}
> }
>
>-static void pnv_pci_ioda1_tce_invalidate(struct pnv_ioda_pe *pe,
>-					 struct iommu_table *tbl,
>-					 __be64 *startp, __be64 *endp, bool rm)
>+static void pnv_pci_ioda1_tce_invalidate(struct iommu_table *tbl,
>+		unsigned long index, unsigned long npages, bool rm)
> {
>+	struct pnv_ioda_pe *pe = tbl->data;
> 	__be64 __iomem *invalidate = rm ?
> 		(__be64 __iomem *)pe->tce_inval_reg_phys :
> 		(__be64 __iomem *)tbl->it_index;
> 	unsigned long start, end, inc;
> 	const unsigned shift = tbl->it_page_shift;
>
>-	start = __pa(startp);
>-	end = __pa(endp);
>+	start = __pa(((__be64 *)tbl->it_base) + index - tbl->it_offset);
>+	end = __pa(((__be64 *)tbl->it_base) + index - tbl->it_offset +
>+			npages - 1);

Platform is the only one knowing the TCE table layout and iommu_table_ops->get()
helps to retrieve TCE entry for the given index. If iommu_table_ops->get() had
returned the address of the TCE entry, not the content. Here, iommu_table_ops->get()
can be reused and we hide the platform specific TCE table layout in iommu_table_ops->get()
backend. However, it's not a big deal and it probably introduces more changes
than expected. You judge it's worthy to do it or improve it later :-)

>
> 	/* BML uses this case for p6/p7/galaxy2: Shift addr and put in node */
> 	if (tbl->it_busno) {
>@@ -1725,16 +1726,39 @@ static void pnv_pci_ioda1_tce_invalidate(struct pnv_ioda_pe *pe,
> 	 */
> }
>
>+static int pnv_ioda1_tce_build(struct iommu_table *tbl, long index,
>+		long npages, unsigned long uaddr,
>+		enum dma_data_direction direction,
>+		struct dma_attrs *attrs)
>+{
>+	long ret = pnv_tce_build(tbl, index, npages, uaddr, direction,
>+			attrs);

The return value from pnv_tce_build() is "int" :-)

>+
>+	if (!ret && (tbl->it_type & TCE_PCI_SWINV_CREATE))
>+		pnv_pci_ioda1_tce_invalidate(tbl, index, npages, false);
>+
>+	return ret;
>+}
>+
>+static void pnv_ioda1_tce_free(struct iommu_table *tbl, long index,
>+		long npages)
>+{
>+	pnv_tce_free(tbl, index, npages);
>+
>+	if (tbl->it_type & TCE_PCI_SWINV_FREE)
>+		pnv_pci_ioda1_tce_invalidate(tbl, index, npages, false);
>+}
>+
> static struct iommu_table_ops pnv_ioda1_iommu_ops = {
>-	.set = pnv_tce_build,
>-	.clear = pnv_tce_free,
>+	.set = pnv_ioda1_tce_build,
>+	.clear = pnv_ioda1_tce_free,
> 	.get = pnv_tce_get,
> };
>
>-static void pnv_pci_ioda2_tce_invalidate(struct pnv_ioda_pe *pe,
>-					 struct iommu_table *tbl,
>-					 __be64 *startp, __be64 *endp, bool rm)
>+static void pnv_pci_ioda2_tce_invalidate(struct iommu_table *tbl,
>+		unsigned long index, unsigned long npages, bool rm)
> {
>+	struct pnv_ioda_pe *pe = tbl->data;
> 	unsigned long start, end, inc;
> 	__be64 __iomem *invalidate = rm ?
> 		(__be64 __iomem *)pe->tce_inval_reg_phys :
>@@ -1747,10 +1771,8 @@ static void pnv_pci_ioda2_tce_invalidate(struct pnv_ioda_pe *pe,
> 	end = start;
>
> 	/* Figure out the start, end and step */
>-	inc = tbl->it_offset + (((u64)startp - tbl->it_base) / sizeof(u64));
>-	start |= (inc << shift);
>-	inc = tbl->it_offset + (((u64)endp - tbl->it_base) / sizeof(u64));
>-	end |= (inc << shift);
>+	start |= (index << shift);
>+	end |= ((index + npages - 1) << shift);
> 	inc = (0x1ull << shift);
> 	mb();
>
>@@ -1763,21 +1785,32 @@ static void pnv_pci_ioda2_tce_invalidate(struct pnv_ioda_pe *pe,
> 	}
> }
>
>-void pnv_pci_ioda_tce_invalidate(struct iommu_table *tbl,
>-				 __be64 *startp, __be64 *endp, bool rm)
>+static int pnv_ioda2_tce_build(struct iommu_table *tbl, long index,
>+		long npages, unsigned long uaddr,
>+		enum dma_data_direction direction,
>+		struct dma_attrs *attrs)
> {
>-	struct pnv_ioda_pe *pe = tbl->data;
>-	struct pnv_phb *phb = pe->phb;
>+	long ret = pnv_tce_build(tbl, index, npages, uaddr, direction,
>+			attrs);

s/long/int

>
>-	if (phb->type == PNV_PHB_IODA1)
>-		pnv_pci_ioda1_tce_invalidate(pe, tbl, startp, endp, rm);
>-	else
>-		pnv_pci_ioda2_tce_invalidate(pe, tbl, startp, endp, rm);
>+	if (!ret && (tbl->it_type & TCE_PCI_SWINV_CREATE))
>+		pnv_pci_ioda2_tce_invalidate(tbl, index, npages, false);
>+
>+	return ret;
>+}
>+
>+static void pnv_ioda2_tce_free(struct iommu_table *tbl, long index,
>+		long npages)
>+{
>+	pnv_tce_free(tbl, index, npages);
>+
>+	if (tbl->it_type & TCE_PCI_SWINV_FREE)
>+		pnv_pci_ioda2_tce_invalidate(tbl, index, npages, false);
> }
>
> static struct iommu_table_ops pnv_ioda2_iommu_ops = {
>-	.set = pnv_tce_build,
>-	.clear = pnv_tce_free,
>+	.set = pnv_ioda2_tce_build,
>+	.clear = pnv_ioda2_tce_free,
> 	.get = pnv_tce_get,
> };
>
>diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
>index 4c3bbb1..84b4ea4 100644
>--- a/arch/powerpc/platforms/powernv/pci.c
>+++ b/arch/powerpc/platforms/powernv/pci.c
>@@ -577,37 +577,28 @@ int pnv_tce_build(struct iommu_table *tbl, long index, long npages,
> 		struct dma_attrs *attrs)
> {
> 	u64 proto_tce = iommu_direction_to_tce_perm(direction);
>-	__be64 *tcep, *tces;
>+	__be64 *tcep;
> 	u64 rpn;
>
>-	tces = tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
>+	tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
> 	rpn = __pa(uaddr) >> tbl->it_page_shift;
>
> 	while (npages--)
> 		*(tcep++) = cpu_to_be64(proto_tce |
> 				(rpn++ << tbl->it_page_shift));
>
>-	/* Some implementations won't cache invalid TCEs and thus may not
>-	 * need that flush. We'll probably turn it_type into a bit mask
>-	 * of flags if that becomes the case
>-	 */
>-	if (tbl->it_type & TCE_PCI_SWINV_CREATE)
>-		pnv_pci_ioda_tce_invalidate(tbl, tces, tcep - 1, false);
>
> 	return 0;
> }
>
> void pnv_tce_free(struct iommu_table *tbl, long index, long npages)
> {
>-	__be64 *tcep, *tces;
>+	__be64 *tcep;
>
>-	tces = tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
>+	tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
>
> 	while (npages--)
> 		*(tcep++) = cpu_to_be64(0);
>-
>-	if (tbl->it_type & TCE_PCI_SWINV_FREE)
>-		pnv_pci_ioda_tce_invalidate(tbl, tces, tcep - 1, false);
> }
>
> unsigned long pnv_tce_get(struct iommu_table *tbl, long index)
>-- 
>2.4.0.rc3.8.gfb3e7d5
>