linux-kernel - Re: [PATCH v10 0/4] PCI: X-Gene: Add APM X-Gene v1 MSI/MSIX termination driver

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Message-ID: <20150605210500.GQ3631@google.com>
Date:	Fri, 5 Jun 2015 16:05:00 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Duc Dang <dhdang@....com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Grant Likely <grant.likely@...aro.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Mark Rutland <mark.rutland@....com>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Tanmay Inamdar <tinamdar@....com>, Loc Ho <lho@....com>,
	Feng Kan <fkan@....com>
Subject: Re: [PATCH v10 0/4] PCI: X-Gene: Add APM X-Gene v1 MSI/MSIX
 termination driver

On Fri, May 29, 2015 at 11:24:28AM -0700, Duc Dang wrote:
> This patch set adds MSI/MSIX termination driver support for APM X-Gene v1 SoC.
> APM X-Gene v1 SoC supports its own implementation of MSI, which is not compliant
> to GIC V2M specification for MSI Termination.
> 
> There is single MSI block in X-Gene v1 SOC which serves all 5 PCIe ports.
> This MSI block supports 2048 MSI termination ports coalesced into 16 physical
> HW IRQ lines and shared across all 5 PCIe ports. Starting from version 5 of
> this patch series, the total MSI vectors this driver supports is reduced to 256
> to maintain the correct set_affinity behavior for each MSI.
> 
> v10 changes:
> 	1. Remove inline in helper functions
> 	2. Simplify hwirq_to_cpu implementation
> 
> v9 changes:
>         1. Add more helpers for manipulating MSI messages
>         2. Improve code readability
>         3. Make PCI_XGENE_MSI selectable
> 
> v8 changes:
>         1. Add helper to read MSI registers
>         2. Resample interrupt status of the same group after handling interrupts
>            in that group
>         3. Error handling in case fail to allocate CPU mask for affinity setting
> 
> v7 changes:
>         1. Add more error handling cases
>         2. Clear spurious interrupts that may happen during driver probe
>         3. Not using free_irq for chained irqs
>         4. Improve GIC IRQ number look up in chained handler
> 
> v6 changes:
>         1. Correctly allocate MSI with bitmap_find_next_zero_area
>         2. Add notifier for CPU hotplug case
>         3. Driver clean up
>         4. Add more detailed information into device tree binding document
>            and move the device tree binding patch before the driver/dts patch
> 
> v5 changes:
>         1. Implement set_affinity for each MSI by statically allocating 2
> 	   MSI GIC IRQs for each X-Gene CPU core and moving MSI vectors around
> 	   these GIC IRQs to steer them to target CPU core. As a consequence,
> 	   the total MSI vectors that X-Gene v1 supports is reduced to 256.
> 
> v4 changes:
>         1. Remove affinity setting for each MSI
>         2. Add description about register layout, MSI termination address
> 	   and data
>         3. Correct total number of MSI vectors to 2048
>         4. Clean up error messages
>         5. Remove unused module code
> 
> v3 changes:
>         1. Implement MSI support using PCI MSI IRQ domain
>         2. Only use msi_controller to store IRQ domain
> 
> v2 changes:
>         1. Use msi_controller structure
>         2. Remove arch hooks arch_teardown_msi_irqs and arch_setup_msi_irqs
> 
>  .../devicetree/bindings/pci/xgene-pci-msi.txt      |  68 +++
>  MAINTAINERS                                        |   8 +
>  arch/arm64/boot/dts/apm/apm-storm.dtsi             |  27 +
>  drivers/pci/host/Kconfig                           |  10 +
>  drivers/pci/host/Makefile                          |   1 +
>  drivers/pci/host/pci-xgene-msi.c                   | 595 +++++++++++++++++++++
>  drivers/pci/host/pci-xgene.c                       |  21 +
>  7 files changed, 730 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/xgene-pci-msi.txt
>  create mode 100644 drivers/pci/host/pci-xgene-msi.c

I applied these to pci/host-xgene for v4.2, thanks!

I squashed the doc, driver, and maintainer updates into a single patch with
the following changelog:

PCI: xgene: Add APM X-Gene v1 PCIe MSI/MSIX termination driver

APM X-Gene v1 SoC supports its own implementation of MSI, which is not 
compliant to GIC V2M specification for MSI Termination.

There is a single MSI block in X-Gene v1 SOC which serves all 5 PCIe ports.
This MSI block supports 2048 MSI termination ports coalesced into 16
physical HW IRQ lines and shared across all 5 PCIe ports.

As there are only 16 HW IRQs to serve 2048 MSI vectors, to support
set_affinity correctly for each MSI vectors, the 16 HW IRQs are statically
allocated to 8 X-Gene v1 cores (2 HW IRQs for each cores).  To steer MSI 
interrupt to target CPU, MSI vector is moved around these HW IRQs lines.
With this approach, the total MSI vectors this driver supports is reduced
to 256.

[bhelgaas: squash doc, driver, maintainer update]
Signed-off-by: Duc Dang <dhdang@....com>
Signed-off-by: Tanmay Inamdar <tinamdar@....com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Reviewed-by: Marc Zyngier <marc.zyngier@....com>

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