linux-kernel - Re: [PATCH v6 08/14] PCI: cadence: Fix updating Vendor ID and Subsystem Vendor ID register

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Message-ID: <20200709214555.GA939109@bogus>
Date:   Thu, 9 Jul 2020 15:45:55 -0600
From:   Rob Herring <robh@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Tom Joseph <tjoseph@...ence.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 08/14] PCI: cadence: Fix updating Vendor ID and
 Subsystem Vendor ID register

On Wed, Jul 08, 2020 at 03:00:12PM +0530, Kishon Vijay Abraham I wrote:
> Commit 1b79c5284439 ("PCI: cadence: Add host driver for Cadence PCIe
> controller") in order to update Vendor ID, directly wrote to
> PCI_VENDOR_ID register. However PCI_VENDOR_ID in root port configuration
> space is read-only register and writing to it will have no effect.
> Use local management register to configure Vendor ID and Subsystem Vendor
> ID.
> 
> Fixes: 1b79c5284439 ("PCI: cadence: Add host driver for Cadence PCIe controller")
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/pci/controller/cadence/pcie-cadence-host.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index 10127ea71b83..8935f7a37e5a 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -82,6 +82,7 @@ static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
>  {
>  	struct cdns_pcie *pcie = &rc->pcie;
>  	u32 value, ctrl;
> +	u32 id;
>  
>  	/*
>  	 * Set the root complex BAR configuration register:
> @@ -101,8 +102,12 @@ static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
>  	cdns_pcie_writel(pcie, CDNS_PCIE_LM_RC_BAR_CFG, value);
>  
>  	/* Set root port configuration space */
> -	if (rc->vendor_id != 0xffff)
> -		cdns_pcie_rp_writew(pcie, PCI_VENDOR_ID, rc->vendor_id);

If this is read-only, then...

> +	if (rc->vendor_id != 0xffff) {
> +		id = CDNS_PCIE_LM_ID_VENDOR(rc->vendor_id) |
> +			CDNS_PCIE_LM_ID_SUBSYS(rc->vendor_id);
> +		cdns_pcie_writel(pcie, CDNS_PCIE_LM_ID, id);
> +	}
> +
>  	if (rc->device_id != 0xffff)
>  		cdns_pcie_rp_writew(pcie, PCI_DEVICE_ID, rc->device_id);

...isn't this read-only too?

>  
> -- 
> 2.17.1
>