Re: [PATCH 02/10] PCI: designware-ep: Add the doorbell mode of MSI-X in EP mode

From: Andrew Murray <andrew.murray@arm.com>
To: Xiaowei Bao <xiaowei.bao@nxp.com>
Cc: jingoohan1@gmail.com, gustavo.pimentel@synopsys.com,
	bhelgaas@google.com, robh+dt@kernel.org, mark.rutland@arm.com,
	shawnguo@kernel.org, leoyang.li@nxp.com, kishon@ti.com,
	lorenzo.pieralisi@arm.com, arnd@arndb.de,
	gregkh@linuxfoundation.org, minghuan.Lian@nxp.com,
	mingkai.hu@nxp.com, roy.zang@nxp.com, linux-pci@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 02/10] PCI: designware-ep: Add the doorbell mode of MSI-X in EP mode
Date: Thu, 15 Aug 2019 12:53:41 +0100
Message-ID: <20190815115340.GG43882@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190815083716.4715-2-xiaowei.bao@nxp.com>

On Thu, Aug 15, 2019 at 04:37:08PM +0800, Xiaowei Bao wrote:
> Add the doorbell mode of MSI-X in EP mode.
> 
> Signed-off-by: Xiaowei Bao <xiaowei.bao@nxp.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 14 ++++++++++++++
>  drivers/pci/controller/dwc/pcie-designware.h    | 14 ++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 75e2955..e3a7cdf 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -454,6 +454,20 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
>  	return 0;
>  }
>  
> +int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep, u8 func_no,
> +				       u16 interrupt_num)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	u32 msg_data;
> +
> +	msg_data = (func_no << PCIE_MSIX_DOORBELL_PF_SHIFT) |
> +		   (interrupt_num - 1);
> +
> +	dw_pcie_writel_dbi(pci, PCIE_MSIX_DOORBELL, msg_data);
> +
> +	return 0;
> +}
> +
>  int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  			      u16 interrupt_num)

Have I understood correctly that the hardware provides an alternative mechanism
that allows for raising MSI-X interrupts without the bother of reading the
capabilities registers?

If so is there any good reason to keep dw_pcie_ep_raise_msix_irq? (And thus use
it in dw_plat_pcie_ep_raise_irq also)?

>  {
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 2b291e8..cd903e9 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -88,6 +88,11 @@
>  #define PCIE_MISC_CONTROL_1_OFF		0x8BC
>  #define PCIE_DBI_RO_WR_EN		BIT(0)
>  
> +#define PCIE_MSIX_DOORBELL		0x948
> +#define PCIE_MSIX_DOORBELL_PF_SHIFT	24
> +#define PCIE_MSIX_DOORBELL_VF_SHIFT	16
> +#define PCIE_MSIX_DOORBELL_VF_ACTIVE	BIT(15)

The _VF defines are not used, I'd suggest removing them.

Thanks,

Andrew Murray

> +
>  /*
>   * iATU Unroll-specific register definitions
>   * From 4.80 core version the address translation will be made by unroll
> @@ -399,6 +404,8 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
>  			     u8 interrupt_num);
>  int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  			     u16 interrupt_num);
> +int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep, u8 func_no,
> +				       u16 interrupt_num);
>  void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar);
>  #else
>  static inline void dw_pcie_ep_linkup(struct dw_pcie_ep *ep)
> @@ -431,6 +438,13 @@ static inline int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  	return 0;
>  }
>  
> +static inline int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep,
> +						     u8 func_no,
> +						     u16 interrupt_num)
> +{
> +	return 0;
> +}
> +
>  static inline void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
>  {
>  }
> -- 
> 2.9.5
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel