linux-kernel - Re: [PATCH v8 6/8] PCI: cadence: Add support to configure virtual functions

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Message-ID: <20210817153852.GA3016660@bjorn-Precision-5520>
Date:   Tue, 17 Aug 2021 10:38:52 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Tom Joseph <tjoseph@...ence.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Jonathan Corbet <corbet@....net>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Lokesh Vutla <lokeshvutla@...com>
Subject: Re: [PATCH v8 6/8] PCI: cadence: Add support to configure virtual
 functions

On Wed, Aug 11, 2021 at 12:16:54PM +0530, Kishon Vijay Abraham I wrote:
> Now that support for SR-IOV is added in PCIe endpoint core, add support
> to configure virtual functions in the Cadence PCIe EP driver.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../pci/controller/cadence/pcie-cadence-ep.c  | 136 +++++++++++++++---
>  drivers/pci/controller/cadence/pcie-cadence.h |   9 ++
>  2 files changed, 125 insertions(+), 20 deletions(-)

> @@ -92,21 +118,29 @@ static int cdns_pcie_ep_set_bar(struct pci_epc *epc, u8 fn, u8 vfn,
>  
>  	addr0 = lower_32_bits(bar_phys);
>  	addr1 = upper_32_bits(bar_phys);
> -	cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_EP_FUNC_BAR_ADDR0(fn, bar),
> -			 addr0);
> -	cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_EP_FUNC_BAR_ADDR1(fn, bar),
> -			 addr1);
>  
>  	reg = CDNS_PCIE_LM_EP_FUNC_BAR_CFG(bar, fn);
> +	if (vfn == 1)
> +		reg = CDNS_PCIE_LM_EP_VFUNC_BAR_CFG(bar, fn);

Seems sort of weird to compute "reg", then sometimes overwrite it, as
opposed to:

  if (vfn == 1)
    reg = CDNS_PCIE_LM_EP_VFUNC_BAR_CFG(bar, fn);
  else
    reg = CDNS_PCIE_LM_EP_FUNC_BAR_CFG(bar, fn);

Also slightly weird that "vfn" is basically used as a boolean, but
it's actually a u8 virtual function number.  I guess VF 1 is special
and not like the other VFs?

>  	b = (bar < BAR_4) ? bar : bar - BAR_4;
>  
> -	cfg = cdns_pcie_readl(pcie, reg);
> -	cfg &= ~(CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE_MASK(b) |
> -		 CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL_MASK(b));
> -	cfg |= (CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE(b, aperture) |
> -		CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL(b, ctrl));
> -	cdns_pcie_writel(pcie, reg, cfg);
> +	if (vfn == 0 || vfn == 1) {
> +		cfg = cdns_pcie_readl(pcie, reg);
> +		cfg &= ~(CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE_MASK(b) |
> +			 CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL_MASK(b));
> +		cfg |= (CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE(b, aperture) |
> +			CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL(b, ctrl));
> +		cdns_pcie_writel(pcie, reg, cfg);
> +	}
>  
> +	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
> +	cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_EP_FUNC_BAR_ADDR0(fn, bar),
> +			 addr0);
> +	cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_EP_FUNC_BAR_ADDR1(fn, bar),
> +			 addr1);
> +
> +	if (vfn > 0)
> +		epf = &epf->epf[vfn - 1];
>  	epf->epf_bar[bar] = epf_bar;
>  
>  	return 0;
> @@ -122,18 +156,25 @@ static void cdns_pcie_ep_clear_bar(struct pci_epc *epc, u8 fn, u8 vfn,
>  	u32 reg, cfg, b, ctrl;
>  
>  	reg = CDNS_PCIE_LM_EP_FUNC_BAR_CFG(bar, fn);
> +	if (vfn == 1)
> +		reg = CDNS_PCIE_LM_EP_VFUNC_BAR_CFG(bar, fn);

Similar recomputation of "reg".

>  	b = (bar < BAR_4) ? bar : bar - BAR_4;
>  
> -	ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_DISABLED;
> -	cfg = cdns_pcie_readl(pcie, reg);
> -	cfg &= ~(CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE_MASK(b) |
> -		 CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL_MASK(b));
> -	cfg |= CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL(b, ctrl);
> -	cdns_pcie_writel(pcie, reg, cfg);
> +	if (vfn == 0 || vfn == 1) {
> +		ctrl = CDNS_PCIE_LM_BAR_CFG_CTRL_DISABLED;
> +		cfg = cdns_pcie_readl(pcie, reg);
> +		cfg &= ~(CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_APERTURE_MASK(b) |
> +			 CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL_MASK(b));
> +		cfg |= CDNS_PCIE_LM_EP_FUNC_BAR_CFG_BAR_CTRL(b, ctrl);
> +		cdns_pcie_writel(pcie, reg, cfg);
> +	}