Re: [PATCH 01/34] powerpc: use mm zones more sensibly

Christoph Hellwig [off-list ref] writes:

Ben / Michael,

can we get this one queued up for 4.21 to prepare for the DMA work later
on?

I was hoping the PASEMI / NXP regressions could be solved before
merging.

My p5020ds is booting fine with this series, so I'm not sure why it's
causing problems on Christian's machine.

The last time I turned on my PASEMI board it tripped some breakers, so I
need to investigate that before I can help test that.

I'll see how things look on Monday and either merge the commits you
identified or the whole series depending on if there's any more info
from Christian.

cheers

On Wed, Nov 14, 2018 at 09:22:41AM +0100, Christoph Hellwig wrote:

quoted

Powerpc has somewhat odd usage where ZONE_DMA is used for all memory on
common 64-bit configfs, and ZONE_DMA32 is used for 31-bit schemes.

Move to a scheme closer to what other architectures use (and I dare to
say the intent of the system):

 - ZONE_DMA: optionally for memory < 31-bit (64-bit embedded only)
 - ZONE_NORMAL: everything addressable by the kernel
 - ZONE_HIGHMEM: memory > 32-bit for 32-bit kernels

Also provide information on how ZONE_DMA is used by defining
ARCH_ZONE_DMA_BITS.

Contains various fixes from Benjamin Herrenschmidt.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/powerpc/Kconfig                          |  8 +---
 arch/powerpc/include/asm/page.h               |  2 +
 arch/powerpc/include/asm/pgtable.h            |  1 -
 arch/powerpc/kernel/dma-swiotlb.c             |  6 +--
 arch/powerpc/kernel/dma.c                     |  7 +--
 arch/powerpc/mm/mem.c                         | 47 +++++++------------
 arch/powerpc/platforms/85xx/corenet_generic.c | 10 ----
 arch/powerpc/platforms/85xx/qemu_e500.c       |  9 ----
 include/linux/mmzone.h                        |  2 +-
 9 files changed, 25 insertions(+), 67 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8be31261aec8..cffff3613bc1 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -374,9 +374,9 @@ config PPC_ADV_DEBUG_DAC_RANGE
 	depends on PPC_ADV_DEBUG_REGS && 44x
 	default y
 
-config ZONE_DMA32
+config ZONE_DMA
 	bool
-	default y if PPC64
+	default y if PPC_BOOK3E_64
 
 config PGTABLE_LEVELS
 	int

@@ -869,10 +869,6 @@ config ISA
 	  have an IBM RS/6000 or pSeries machine, say Y.  If you have an
 	  embedded board, consult your board documentation.
 
-config ZONE_DMA
-	bool
-	default y
-
 config GENERIC_ISA_DMA
 	bool
 	depends on ISA_DMA_API

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index f6a1265face2..fc8c9ac0c6be 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h

@@ -354,4 +354,6 @@ typedef struct page *pgtable_t;
 #endif /* __ASSEMBLY__ */
 #include <asm/slice.h>
 
+#define ARCH_ZONE_DMA_BITS 31
+
 #endif /* _ASM_POWERPC_PAGE_H */

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 9679b7519a35..8af32ce93c7f 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h

@@ -66,7 +66,6 @@ extern unsigned long empty_zero_page[];
 
 extern pgd_t swapper_pg_dir[];
 
-void limit_zone_pfn(enum zone_type zone, unsigned long max_pfn);
 int dma_pfn_limit_to_zone(u64 pfn_limit);
 extern void paging_init(void);
 

diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c
index 5fc335f4d9cd..678811abccfc 100644
--- a/arch/powerpc/kernel/dma-swiotlb.c
+++ b/arch/powerpc/kernel/dma-swiotlb.c

@@ -108,12 +108,8 @@ int __init swiotlb_setup_bus_notifier(void)
 
 void __init swiotlb_detect_4g(void)
 {
-	if ((memblock_end_of_DRAM() - 1) > 0xffffffff) {
+	if ((memblock_end_of_DRAM() - 1) > 0xffffffff)
 		ppc_swiotlb_enable = 1;
-#ifdef CONFIG_ZONE_DMA32
-		limit_zone_pfn(ZONE_DMA32, (1ULL << 32) >> PAGE_SHIFT);
-#endif
-	}
 }
 
 static int __init check_swiotlb_enabled(void)

diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index dbfc7056d7df..6551685a4ed0 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c

@@ -50,7 +50,7 @@ static int dma_nommu_dma_supported(struct device *dev, u64 mask)
 		return 1;
 
 #ifdef CONFIG_FSL_SOC
-	/* Freescale gets another chance via ZONE_DMA/ZONE_DMA32, however
+	/* Freescale gets another chance via ZONE_DMA, however
 	 * that will have to be refined if/when they support iommus
 	 */
 	return 1;

@@ -94,13 +94,10 @@ void *__dma_nommu_alloc_coherent(struct device *dev, size_t size,
 	}
 
 	switch (zone) {
+#ifdef CONFIG_ZONE_DMA
 	case ZONE_DMA:
 		flag |= GFP_DMA;
 		break;
-#ifdef CONFIG_ZONE_DMA32
-	case ZONE_DMA32:
-		flag |= GFP_DMA32;
-		break;
 #endif
 	};
 #endif /* CONFIG_FSL_SOC */

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 0a64fffabee1..c0b676c3a5ba 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c

@@ -246,35 +246,19 @@ static int __init mark_nonram_nosave(void)
 }
 #endif
 
-static bool zone_limits_final;
-
 /*
- * The memory zones past TOP_ZONE are managed by generic mm code.
- * These should be set to zero since that's what every other
- * architecture does.
+ * Zones usage:
+ *
+ * We setup ZONE_DMA to be 31-bits on all platforms and ZONE_NORMAL to be
+ * everything else. GFP_DMA32 page allocations automatically fall back to
+ * ZONE_DMA.
+ *
+ * By using 31-bit unconditionally, we can exploit ARCH_ZONE_DMA_BITS to
+ * inform the generic DMA mapping code.  32-bit only devices (if not handled
+ * by an IOMMU anyway) will take a first dip into ZONE_NORMAL and get
+ * otherwise served by ZONE_DMA.
  */
-static unsigned long max_zone_pfns[MAX_NR_ZONES] = {
-	[0            ... TOP_ZONE        ] = ~0UL,
-	[TOP_ZONE + 1 ... MAX_NR_ZONES - 1] = 0
-};
-
-/*
- * Restrict the specified zone and all more restrictive zones
- * to be below the specified pfn.  May not be called after
- * paging_init().
- */
-void __init limit_zone_pfn(enum zone_type zone, unsigned long pfn_limit)
-{
-	int i;
-
-	if (WARN_ON(zone_limits_final))
-		return;
-
-	for (i = zone; i >= 0; i--) {
-		if (max_zone_pfns[i] > pfn_limit)
-			max_zone_pfns[i] = pfn_limit;
-	}
-}
+static unsigned long max_zone_pfns[MAX_NR_ZONES];
 
 /*
  * Find the least restrictive zone that is entirely below the

@@ -324,11 +308,14 @@ void __init paging_init(void)
 	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 	       (long int)((top_of_ram - total_ram) >> 20));
 
+#ifdef CONFIG_ZONE_DMA
+	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn, 0x7fffffffUL >> PAGE_SHIFT);
+#endif
+	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
 #ifdef CONFIG_HIGHMEM
-	limit_zone_pfn(ZONE_NORMAL, lowmem_end_addr >> PAGE_SHIFT);
+	max_zone_pfns[ZONE_HIGHMEM] = max_pfn;
 #endif
-	limit_zone_pfn(TOP_ZONE, top_of_ram >> PAGE_SHIFT);
-	zone_limits_final = true;
+
 	free_area_init_nodes(max_zone_pfns);
 
 	mark_nonram_nosave();

diff --git a/arch/powerpc/platforms/85xx/corenet_generic.c b/arch/powerpc/platforms/85xx/corenet_generic.c
index ac191a7a1337..b0dac307bebf 100644
--- a/arch/powerpc/platforms/85xx/corenet_generic.c
+++ b/arch/powerpc/platforms/85xx/corenet_generic.c

@@ -68,16 +68,6 @@ void __init corenet_gen_setup_arch(void)
 
 	swiotlb_detect_4g();
 
-#if defined(CONFIG_FSL_PCI) && defined(CONFIG_ZONE_DMA32)
-	/*
-	 * Inbound windows don't cover the full lower 4 GiB
-	 * due to conflicts with PCICSRBAR and outbound windows,
-	 * so limit the DMA32 zone to 2 GiB, to allow consistent
-	 * allocations to succeed.
-	 */
-	limit_zone_pfn(ZONE_DMA32, 1UL << (31 - PAGE_SHIFT));
-#endif
-
 	pr_info("%s board\n", ppc_md.name);
 
 	mpc85xx_qe_init();

diff --git a/arch/powerpc/platforms/85xx/qemu_e500.c b/arch/powerpc/platforms/85xx/qemu_e500.c
index b63a8548366f..27631c607f3d 100644
--- a/arch/powerpc/platforms/85xx/qemu_e500.c
+++ b/arch/powerpc/platforms/85xx/qemu_e500.c

@@ -45,15 +45,6 @@ static void __init qemu_e500_setup_arch(void)
 
 	fsl_pci_assign_primary();
 	swiotlb_detect_4g();
-#if defined(CONFIG_FSL_PCI) && defined(CONFIG_ZONE_DMA32)
-	/*
-	 * Inbound windows don't cover the full lower 4 GiB
-	 * due to conflicts with PCICSRBAR and outbound windows,
-	 * so limit the DMA32 zone to 2 GiB, to allow consistent
-	 * allocations to succeed.
-	 */
-	limit_zone_pfn(ZONE_DMA32, 1UL << (31 - PAGE_SHIFT));
-#endif
 	mpc85xx_smp_init();
 }
 

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 847705a6d0ec..e2d01ccd071d 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h

@@ -314,7 +314,7 @@ enum zone_type {
 	 * Architecture		Limit
 	 * ---------------------------
 	 * parisc, ia64, sparc	<4G
-	 * s390			<2G
+	 * s390, powerpc	<2G
 	 * arm			Various
 	 * alpha		Unlimited or 0-16MB.
 	 *

-- 
2.19.1

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