Re: [PATCH v6 5/6] PCI: fu740: Add SiFive FU740 PCIe host controller driver

Lorenzo Pieralisi
2021-05-04T14:24:07Z

On Tue, May 04, 2021 at 08:46:32AM -0500, Bjorn Helgaas wrote:
> On Tue, May 04, 2021 at 06:59:39PM +0800, Greentime Hu wrote:
> > From: Paul Walmsley <paul.walmsley@sifive.com>
> >
> > Add driver for the SiFive FU740 PCIe host controller.
> > This controller is based on the DesignWare PCIe core.
> >
> > Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> > Co-developed-by: Henry Styles <hes@sifive.com>
> > Signed-off-by: Henry Styles <hes@sifive.com>
> > Co-developed-by: Erik Danie <erik.danie@sifive.com>
> > Signed-off-by: Erik Danie <erik.danie@sifive.com>
> > Co-developed-by: Greentime Hu <greentime.hu@sifive.com>
> > Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
> > ---
> > drivers/pci/controller/dwc/Kconfig | 10 +
> > drivers/pci/controller/dwc/Makefile | 1 +
> > drivers/pci/controller/dwc/pcie-fu740.c | 309 ++++++++++++++++++++++++
> > 3 files changed, 320 insertions(+)
> > create mode 100644 drivers/pci/controller/dwc/pcie-fu740.c
> >
> > diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> > index 22c5529e9a65..255d43b1661b 100644
> > --- a/drivers/pci/controller/dwc/Kconfig
> > +++ b/drivers/pci/controller/dwc/Kconfig
> > @@ -318,4 +318,14 @@ config PCIE_AL
> > required only for DT-based platforms. ACPI platforms with the
> > Annapurna Labs PCIe controller don't need to enable this.
> >
> > +config PCIE_FU740
> > + bool "SiFive FU740 PCIe host controller"
> > + depends on PCI_MSI_IRQ_DOMAIN
> > + depends on SOC_SIFIVE || COMPILE_TEST
> > + depends on GPIOLIB
>
> 1) I'm a little disappointed that I reported the build issue 6 days
> ago when we were already in the merge window, and it's taken until
> now to make some progress.
>
> 2) I would prefer not to depend on GPIOLIB because it reduces
> compile-test coverage. For example, the x86_64 defconfig does not
> enable GPIOLIB, so one must manually enable it to even be able to
> enable PCIE_FU740.
>
> Many other PCI controller drivers use GPIO, but no others depend on
> GPIOLIB, so I infer that in the !GPIOLIB case, gpio/consumer.h
> provides the stubs required for compile testing.
>
> We could have a conversation about whether it's better to
> explicitly depend on GPIOLIB here, or whether building a working
> FU740 driver implicitly depends on GPIOLIB being selected
> elsewhere. That implicit dependency *is* a little obscure, but I
> think that's what other drivers currently do, and I'd like to do
> this consistently unless there's a good reason otherwise.

I will drop the explicit GPIOLIB dependency and push it out. For (1) I
agree with you - I merged when I received some input - it is reasonable
to avoid adding it to v5.13 material for this reason, apologies.

Thanks,
Lorenzo

> Here are some examples of other drivers:
>
> dwc/pci-dra7xx.c:
> config PCI_DRA7XX_HOST
> depends on SOC_DRA7XX || COMPILE_TEST
>
> config SOC_DRA7XX
> select ARCH_OMAP2PLUS
>
> config ARCH_OMAP2PLUS
> select GPIOLIB
>
> dwc/pci-meson.c:
> config PCI_MESON
> # doesn't, but probably *should* depend on "ARCH_MESON || COMPILE_TEST"
>
> menuconfig ARCH_MESON
> select GPIOLIB
>
> dwc/pcie-qcom.c:
> config PCIE_QCOM
> depends on OF && (ARCH_QCOM || COMPILE_TEST)
>
> config ARCH_QCOM
> select GPIOLIB
>
> pcie-rockchip.c:
> config PCIE_ROCKCHIP_HOST
> depends on ARCH_ROCKCHIP || COMPILE_TEST
>
> config ARCH_ROCKCHIP
> select GPIOLIB
>
> > + select PCIE_DW_HOST
> > + help
> > + Say Y here if you want PCIe controller support for the SiFive
> > + FU740.
> > +
> > endmenu