[v5,11/12] ARM64: add dma remap for BrcmSTB PCIe

Message ID 1537367527-20773-12-git-send-email-jim2101024@gmail.com
State New
Delegated to: Lorenzo Pieralisi
Headers show
Series
  • PCI: brcmstb: Add Broadcom Settopbox PCIe support (resend)
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Commit Message

Jim Quinlan Sept. 19, 2018, 2:32 p.m.
The BrcmSTB PCIe controller needs to remap DMA accesses to it because
of the requirements of its interface with the SOC memory controllers.

Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
---
 drivers/pci/controller/Kconfig        |  1 +
 drivers/pci/controller/pcie-brcmstb.c | 12 ++++++++++++
 2 files changed, 13 insertions(+)

Comments

Christoph Hellwig Sept. 19, 2018, 2:41 p.m. | #1
On Wed, Sep 19, 2018 at 10:32:06AM -0400, Jim Quinlan wrote:
> +#if defined(CONFIG_ARM64)

Please use plain #ifdef where possible.

> +dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	return brcm_phys_to_dma(dev, paddr);
> +}
> +
> +phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> +{
> +	return brcm_dma_to_phys(dev, dev_addr);
> +}
> +#endif

How is this going to work for a kernel with BrcmSTB built in, but running
on a more standard arm64 SOC?

I suspect we really just want a set of ranges hanging off struct device
(conditional on a config option).  Each SoC can then fill it at boot
time, and if it is non-NULL the DMA code will use it instead of
calling __phys_to_dma and __dma_to_phys.  In fact the single range
version could probably just replace the existing dma_pfn_offset
field.
Jim Quinlan Sept. 21, 2018, 6:29 p.m. | #2
On Wed, Sep 19, 2018 at 10:41 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Wed, Sep 19, 2018 at 10:32:06AM -0400, Jim Quinlan wrote:
> > +#if defined(CONFIG_ARM64)
>
> Please use plain #ifdef where possible.
>
> > +dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
> > +{
> > +     return brcm_phys_to_dma(dev, paddr);
> > +}
> > +
> > +phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> > +{
> > +     return brcm_dma_to_phys(dev, dev_addr);
> > +}
> > +#endif
>
> How is this going to work for a kernel with BrcmSTB built in, but running
> on a more standard arm64 SOC?

Sorry for the delay in my response.  It would work because the
dma_ranges would be empty/null and identity mapping would happen, but
yes, all __dma_to_phys and __phys_to_dma calls would be wasting time
going through the brcm functions.  We would have to take BRCMSTB=y out
of the defconfig.  Florian would probably NAK that idea.

Please remember that the reason for this approach is because in your
response to V4 you suggested that "Override phys_to_dma and
dma_to_phys as mips and x86 [sta2x11] do for similar situations"  and
"Overriding phys_to_dma and dma_to_phys is required if you need to
support swiotlb, and chances are with a broken PCIe controller on
arm64 or mips64 you eventuall will".

>
> I suspect we really just want a set of ranges hanging off struct device
> (conditional on a config option).  Each SoC can then fill it at boot
> time, and if it is non-NULL the DMA code will use it instead of
> calling __phys_to_dma and __dma_to_phys.  In fact the single range
> version could probably just replace the existing dma_pfn_offset
> field.
If this was a config option then BRCMSTB=y in defconfig would set this
for all ARM64, just like the above case, correct?  And would this work
with SWIOTLB?   Also, do you think others would use it, or would I be
adding code in the DMA API only because of one unusual PCIe host
controller design?   Keep in mind that although you didn't like the
approach of V4 --  which intercepted DMA ops to make the appropriate
mapping and was not compatible with SWIOTLB -- at least it kept the
code restricted to oru driver.

Thanks,
Jim

Patch

diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
index 8daa621..4394430 100644
--- a/drivers/pci/controller/Kconfig
+++ b/drivers/pci/controller/Kconfig
@@ -284,6 +284,7 @@  config PCIE_BRCMSTB
 	depends on OF && PCI_MSI
 	depends on SOC_BRCMSTB
 	default ARCH_BRCMSTB || BMIPS_GENERIC
+	select ARCH_HAS_PHYS_TO_DMA if ARM64
 	help
 	  Say Y here to enable PCIe host controller support for
 	  Broadcom Settop Box SOCs.  A Broadcom SOC will may have
diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index a805d87..ae9df8e 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -974,6 +974,18 @@  phys_addr_t brcm_dma_to_phys(struct device *dev, dma_addr_t dev_addr)
 	return (phys_addr_t)dev_addr;
 }
 
+#if defined(CONFIG_ARM64)
+dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+	return brcm_phys_to_dma(dev, paddr);
+}
+
+phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
+{
+	return brcm_dma_to_phys(dev, dev_addr);
+}
+#endif
+
 static int brcm_pcie_add_controller(struct brcm_pcie *pcie)
 {
 	int i, ret = 0;