[PATCH v2 0/2] x86: Get rid of custom DMA functions

[PATCH v2 0/2] x86: Get rid of custom DMA functions

[Nicolas Saenz Julienne]

sta2x11 is the only x86 device that depends custom DMA direct functions.
It turns out it can be made standard by carefully setting the device's
DMA masks and offset.

Originally only patch #2 was sent but I realised patch #1 is also
needed, which is a good addition as it's also a prerequisite to get
proper DMA support on the Raspberry Pi 4[1].

[1] https://lkml.org/lkml/2019/10/15/523

---

Changes since v1:
  - Small cleanups in sta2x11-fixup.x
  - add patch checking DMA addresses lower bounds

Nicolas Saenz Julienne (2):
  dma-direct: check for overflows on 32 bit DMA addresses
  x86/PCI: sta2x11: use default DMA address translation ops

 arch/x86/Kconfig                  |   1 -
 arch/x86/include/asm/device.h     |   3 -
 arch/x86/include/asm/dma-direct.h |   9 --
 arch/x86/pci/sta2x11-fixup.c      | 135 ++++++------------------------
 include/linux/dma-direct.h        |   8 ++
 5 files changed, 34 insertions(+), 122 deletions(-)
 delete mode 100644 arch/x86/include/asm/dma-direct.h

-- 
2.23.0

[PATCH v2 2/2] x86/PCI: sta2x11: use default DMA address translation

[Nicolas Saenz Julienne]

The devices found behind this PCIe chip have unusual DMA mapping
constraints as there is an AMBA interconnect placed in between them and
the different PCI endpoints. The offset between physical memory
addresses and AMBA's view is provided by reading a PCI config register,
which is saved and used whenever DMA mapping is needed.

It turns out that this DMA setup can be represented by properly setting
'dma_pfn_offset', 'dma_bus_mask' and 'dma_mask' during the PCI device
enable fixup. And ultimately allows us to get rid of this device's
custom DMA functions.

Aside from the code deletion and DMA setup, sta2x11_pdev_to_mapping() is
moved to avoid warnings whenever CONFIG_PM is not enabled.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---

Changed since v1:
  - use variable to avoid recalculating AMBA's max address
  - remove x86's dma-direct.h as it's not longer needed

Note: This was only compile tested. Also, there was some conversation
      here: https://lkml.org/lkml/2019/10/17/1014, that Christoph might
      have missed as I misspelled his email on v1.

 arch/x86/Kconfig                  |   1 -
 arch/x86/include/asm/device.h     |   3 -
 arch/x86/include/asm/dma-direct.h |   9 --
 arch/x86/pci/sta2x11-fixup.c      | 135 ++++++------------------------
 4 files changed, 26 insertions(+), 122 deletions(-)
 delete mode 100644 arch/x86/include/asm/dma-direct.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index abe822d52167..9c2a51e1cb59 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -708,7 +708,6 @@ config X86_SUPPORTS_MEMORY_FAILURE
 config STA2X11
 	bool "STA2X11 Companion Chip Support"
 	depends on X86_32_NON_STANDARD && PCI
-	select ARCH_HAS_PHYS_TO_DMA
 	select SWIOTLB
 	select MFD_STA2X11
 	select GPIOLIB
diff --git a/arch/x86/include/asm/device.h b/arch/x86/include/asm/device.h
index a8f6c809d9b1..5e12c63b47aa 100644
--- a/arch/x86/include/asm/device.h
+++ b/arch/x86/include/asm/device.h
@@ -6,9 +6,6 @@ struct dev_archdata {
 #if defined(CONFIG_INTEL_IOMMU) || defined(CONFIG_AMD_IOMMU)
 	void *iommu; /* hook for IOMMU specific extension */
 #endif
-#ifdef CONFIG_STA2X11
-	bool is_sta2x11;
-#endif
 };
 
 #if defined(CONFIG_X86_DEV_DMA_OPS) && defined(CONFIG_PCI_DOMAINS)
diff --git a/arch/x86/include/asm/dma-direct.h b/arch/x86/include/asm/dma-direct.h
deleted file mode 100644
index 1a19251eaac9..000000000000
--- a/arch/x86/include/asm/dma-direct.h
+++ /dev/null
@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef ASM_X86_DMA_DIRECT_H
-#define ASM_X86_DMA_DIRECT_H 1
-
-bool dma_capable(struct device *dev, dma_addr_t addr, size_t size);
-dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr);
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr);
-
-#endif /* ASM_X86_DMA_DIRECT_H */
diff --git a/arch/x86/pci/sta2x11-fixup.c b/arch/x86/pci/sta2x11-fixup.c
index 6269a175385d..4a631264b809 100644
--- a/arch/x86/pci/sta2x11-fixup.c
+++ b/arch/x86/pci/sta2x11-fixup.c
@@ -30,7 +30,6 @@ struct sta2x11_ahb_regs { /* saved during suspend */
 };
 
 struct sta2x11_mapping {
-	u32 amba_base;
 	int is_suspended;
 	struct sta2x11_ahb_regs regs[STA2X11_NR_FUNCS];
 };
@@ -92,18 +91,6 @@ static int sta2x11_pdev_to_ep(struct pci_dev *pdev)
 	return pdev->bus->number - instance->bus0;
 }
 
-static struct sta2x11_mapping *sta2x11_pdev_to_mapping(struct pci_dev *pdev)
-{
-	struct sta2x11_instance *instance;
-	int ep;
-
-	instance = sta2x11_pdev_to_instance(pdev);
-	if (!instance)
-		return NULL;
-	ep = sta2x11_pdev_to_ep(pdev);
-	return instance->map + ep;
-}
-
 /* This is exported, as some devices need to access the MFD registers */
 struct sta2x11_instance *sta2x11_get_instance(struct pci_dev *pdev)
 {
@@ -111,39 +98,6 @@ struct sta2x11_instance *sta2x11_get_instance(struct pci_dev *pdev)
 }
 EXPORT_SYMBOL(sta2x11_get_instance);
 
-
-/**
- * p2a - Translate physical address to STA2x11 AMBA address,
- *       used for DMA transfers to STA2x11
- * @p: Physical address
- * @pdev: PCI device (must be hosted within the connext)
- */
-static dma_addr_t p2a(dma_addr_t p, struct pci_dev *pdev)
-{
-	struct sta2x11_mapping *map;
-	dma_addr_t a;
-
-	map = sta2x11_pdev_to_mapping(pdev);
-	a = p + map->amba_base;
-	return a;
-}
-
-/**
- * a2p - Translate STA2x11 AMBA address to physical address
- *       used for DMA transfers from STA2x11
- * @a: STA2x11 AMBA address
- * @pdev: PCI device (must be hosted within the connext)
- */
-static dma_addr_t a2p(dma_addr_t a, struct pci_dev *pdev)
-{
-	struct sta2x11_mapping *map;
-	dma_addr_t p;
-
-	map = sta2x11_pdev_to_mapping(pdev);
-	p = a - map->amba_base;
-	return p;
-}
-
 /* At setup time, we use our own ops if the device is a ConneXt one */
 static void sta2x11_setup_pdev(struct pci_dev *pdev)
 {
@@ -151,70 +105,12 @@ static void sta2x11_setup_pdev(struct pci_dev *pdev)
 
 	if (!instance) /* either a sta2x11 bridge or another ST device */
 		return;
-	pci_set_consistent_dma_mask(pdev, STA2X11_AMBA_SIZE - 1);
-	pci_set_dma_mask(pdev, STA2X11_AMBA_SIZE - 1);
-	pdev->dev.archdata.is_sta2x11 = true;
 
 	/* We must enable all devices as master, for audio DMA to work */
 	pci_set_master(pdev);
 }
 DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_STMICRO, PCI_ANY_ID, sta2x11_setup_pdev);
 
-/*
- * The following three functions are exported (used in swiotlb: FIXME)
- */
-/**
- * dma_capable - Check if device can manage DMA transfers (FIXME: kill it)
- * @dev: device for a PCI device
- * @addr: DMA address
- * @size: DMA size
- */
-bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
-{
-	struct sta2x11_mapping *map;
-
-	if (!dev->archdata.is_sta2x11) {
-		if (!dev->dma_mask)
-			return false;
-		return addr + size - 1 <= *dev->dma_mask;
-	}
-
-	map = sta2x11_pdev_to_mapping(to_pci_dev(dev));
-
-	if (!map || (addr < map->amba_base))
-		return false;
-	if (addr + size >= map->amba_base + STA2X11_AMBA_SIZE) {
-		return false;
-	}
-
-	return true;
-}
-
-/**
- * __phys_to_dma - Return the DMA AMBA address used for this STA2x11 device
- * @dev: device for a PCI device
- * @paddr: Physical address
- */
-dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
-{
-	if (!dev->archdata.is_sta2x11)
-		return paddr;
-	return p2a(paddr, to_pci_dev(dev));
-}
-
-/**
- * dma_to_phys - Return the physical address used for this STA2x11 DMA address
- * @dev: device for a PCI device
- * @daddr: STA2x11 AMBA DMA address
- */
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
-{
-	if (!dev->archdata.is_sta2x11)
-		return daddr;
-	return a2p(daddr, to_pci_dev(dev));
-}
-
-
 /*
  * At boot we must set up the mappings for the pcie-to-amba bridge.
  * It involves device access, and the same happens at suspend/resume time
@@ -234,12 +130,22 @@ phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
 /* At probe time, enable mapping for each endpoint, using the pdev */
 static void sta2x11_map_ep(struct pci_dev *pdev)
 {
-	struct sta2x11_mapping *map = sta2x11_pdev_to_mapping(pdev);
+	struct sta2x11_instance *instance = sta2x11_pdev_to_instance(pdev);
+	struct device *dev = &pdev->dev;
+	u32 amba_base, max_amba_addr;
 	int i;
 
-	if (!map)
+	if (!instance)
 		return;
-	pci_read_config_dword(pdev, AHB_BASE(0), &map->amba_base);
+
+	pci_read_config_dword(pdev, AHB_BASE(0), &amba_base);
+	max_amba_addr = amba_base + STA2X11_AMBA_SIZE - 1;
+
+	dev->dma_pfn_offset = PFN_DOWN(-amba_base);
+
+	dev->bus_dma_mask = max_amba_addr;
+	pci_set_consistent_dma_mask(pdev, max_amba_addr);
+	pci_set_dma_mask(pdev, max_amba_addr);
 
 	/* Configure AHB mapping */
 	pci_write_config_dword(pdev, AHB_PEXLBASE(0), 0);
@@ -253,13 +159,24 @@ static void sta2x11_map_ep(struct pci_dev *pdev)
 
 	dev_info(&pdev->dev,
 		 "sta2x11: Map EP %i: AMBA address %#8x-%#8x\n",
-		 sta2x11_pdev_to_ep(pdev),  map->amba_base,
-		 map->amba_base + STA2X11_AMBA_SIZE - 1);
+		 sta2x11_pdev_to_ep(pdev), amba_base, max_amba_addr);
 }
 DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_STMICRO, PCI_ANY_ID, sta2x11_map_ep);
 
 #ifdef CONFIG_PM /* Some register values must be saved and restored */
 
+static struct sta2x11_mapping *sta2x11_pdev_to_mapping(struct pci_dev *pdev)
+{
+	struct sta2x11_instance *instance;
+	int ep;
+
+	instance = sta2x11_pdev_to_instance(pdev);
+	if (!instance)
+		return NULL;
+	ep = sta2x11_pdev_to_ep(pdev);
+	return instance->map + ep;
+}
+
 static void suspend_mapping(struct pci_dev *pdev)
 {
 	struct sta2x11_mapping *map = sta2x11_pdev_to_mapping(pdev);
-- 
2.23.0

Re: [PATCH v2 2/2] x86/PCI: sta2x11: use default DMA address translation

[Christoph Hellwig]

On Fri, Oct 18, 2019 at 01:00:44PM +0200, Nicolas Saenz Julienne wrote:
> The devices found behind this PCIe chip have unusual DMA mapping
> constraints as there is an AMBA interconnect placed in between them and
> the different PCI endpoints. The offset between physical memory
> addresses and AMBA's view is provided by reading a PCI config register,
> which is saved and used whenever DMA mapping is needed.
> 
> It turns out that this DMA setup can be represented by properly setting
> 'dma_pfn_offset', 'dma_bus_mask' and 'dma_mask' during the PCI device
> enable fixup. And ultimately allows us to get rid of this device's
> custom DMA functions.
> 
> Aside from the code deletion and DMA setup, sta2x11_pdev_to_mapping() is
> moved to avoid warnings whenever CONFIG_PM is not enabled.

Looks sensible to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>

But I can't tested it either, and kinda wonder if this code is actually
still used by anyone..

Re: [PATCH v2 2/2] x86/PCI: sta2x11: use default DMA address translation

[Nicolas Saenz Julienne]

[-- Attachment #1: Type: text/plain, Size: 1174 bytes --]

On Wed, 2019-10-30 at 14:45 -0700, Christoph Hellwig wrote:
> On Fri, Oct 18, 2019 at 01:00:44PM +0200, Nicolas Saenz Julienne wrote:
> > The devices found behind this PCIe chip have unusual DMA mapping
> > constraints as there is an AMBA interconnect placed in between them and
> > the different PCI endpoints. The offset between physical memory
> > addresses and AMBA's view is provided by reading a PCI config register,
> > which is saved and used whenever DMA mapping is needed.
> > 
> > It turns out that this DMA setup can be represented by properly setting
> > 'dma_pfn_offset', 'dma_bus_mask' and 'dma_mask' during the PCI device
> > enable fixup. And ultimately allows us to get rid of this device's
> > custom DMA functions.
> > 
> > Aside from the code deletion and DMA setup, sta2x11_pdev_to_mapping() is
> > moved to avoid warnings whenever CONFIG_PM is not enabled.
> 
> Looks sensible to me:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> But I can't tested it either, and kinda wonder if this code is actually
> still used by anyone..

Maybe Alessandro can shine some light on this (though I wonder his mail is stil
valid).


[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v2 2/2] x86/PCI: sta2x11: use default DMA address translation

[Alessandro Rubini]

>> But I can't tested it either, and kinda wonder if this code is actually
>> still used by anyone..

I wonder too.
 
> Maybe Alessandro can shine some light on this (though I wonder his
> mail is stil valid).

Yes, the mail is valid, and I'm busy as usual.

Now, this STA2X11 is a chipset by ST-Ericcson that was bringing the
AMBA peripherals to the PC world. It was meant to be used as an I/O
device in the automotive sector, as far as I know (the audio part had
features aimed at automotive installations).  I'm sure the chip was
never used in standard PC's -- the eval board was a PCIe slot, but
that's it.

So, I can't test and I don't know if there are users of this chip.
If there are users, they are big numbers.  I think we can accept any
clean-up patch on the code base: if anything goes wrong, the users
will surface with a fix when they'll consider an upgrade to their
installed systems.

/alessndro