On 03/12/2019 4:31 pm, Jeremy Linton wrote:
Hi,
On 11/26/19 3:19 AM, Nicolas Saenz Julienne wrote:
From: Jim Quinlan <james.quinlan@xxxxxxxxxxxx>
This adds a basic driver for Broadcom's STB PCIe controller, for now
aimed at Raspberry Pi 4's SoC, bcm2711.
Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx>
Co-developed-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
Changes since v2:
- Correct rc_bar2_offset sign
- Invert IRQ clear and masking in setup code
- Use bitfield.h, redo all register ops while keeping the register
names intact
- Remove all SHIFT register definitions
- Get rid of all _RB writes
- Get rid of of_data
- Don't iterate over inexisting dma-ranges
- Add comment regarding dma-ranges validation
- Small cosmetic cleanups
- Fix license mismatch
- Set driver Kconfig tristate
- Didn't add any comment about the controller not being I/O coherent
for now as I wait for Jeremy's reply
I guess its fine.. In answer to the original query. It seems that this
PCIe bridge requires explicit cache operations for DMA from PCIe
endpoints. This wasn't obvious to me at first reading because I was
assuming the custom DMA ops were strictly to deal with the stated DMA
limits.
FWIW, although it might seem anathema to server folks, non-coherent PCI
is the overwhelming norm in embedded SoCs. Either way, provided the
presence or absence of coherency is correctly described via the DT
"dma-coherent" or ACPI _CCA property, then it's transparently handled by
the DMA API for the endpoint drivers and irrelevant to the host bridge
itself - after all, in principle the exact same root complex IP could be
integrated both coherently and non-coherently in different SoCs.
Robin.
So if you end up respinning, it still might be worthy mentioning
somewhere that this is a non-coherent PCIe implementation. I still hold
much of my original reservations about pieces of this driver.
Particularly, how it might look if someone wanted to boot the RPi using
ACPI on linux. But, I was shown a clever bit of AML recently, which
solves those problems for the RPi and the attached XHCI.
So, given how much time I've looked at the root port configuration/etc
sections of this driver and I've not found a serious bug:
Reviewed-by: Jeremy Linton <jeremy.linton@xxxxxxx>
Changes since v1:
- Fix Kconfig
- Remove pci domain check
- Remove all MSI related code
- Remove supend/resume code
- Simplify link state wait routine
- Prefix all functions
- Use of_device_get_match_data()
- Use devm_clk_get_optional()
- Get rid of irq variable
- Use STB all over the driver
- Simplify map_bus() function
- Fix license mismatch
- Remove unused register definitions
- Small cleanups, spell errors
This is based on Jim's original submission[1] but adapted and tailored
specifically to bcm2711's needs (that's the Raspberry Pi 4). Support for
the rest of the brcmstb family will soon follow once we get support for
multiple dma-ranges in dma/direct.
[1] https://patchwork.kernel.org/patch/10605959/
drivers/pci/controller/Kconfig | 8 +
drivers/pci/controller/Makefile | 1 +
drivers/pci/controller/pcie-brcmstb.c | 753 ++++++++++++++++++++++++++
3 files changed, 762 insertions(+)
create mode 100644 drivers/pci/controller/pcie-brcmstb.c
Thanks,
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