[PATCH] arm: a37xx: pci: Implement workaround for the readback value of VEND_ID

[Stefan Roese]

On 03.03.21 14:37, Pali Rohár wrote:
> Marvell Armada 3720 Functional Errata, Guidelines, and Restrictions
> document describes in erratum 4.1 PCIe value of vendor ID (Ref #: 243):
> 
>      The readback value of VEND_ID (RD0070000h [15:0]) is 1B4Bh, while it
>      should read 11ABh.
> 
>      The firmware can write the correct value, 11ABh, through VEND_ID
>      (RD0076044h [15:0]).
> 
> Implement this workaround in U-Boot PCIe controller driver aardvark for
> both PCI vendor id and PCI subsystem vendor id.
> 
> This change affects PCI vendor id of PCIe root bridge emulated by Linux
> kernel. With this change Linux kernel reports correct vendor id 11AB.
> 
> Signed-off-by: Pali Rohár <pali at kernel.org>
> ---
>   drivers/pci/pci-aardvark.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/pci-aardvark.c b/drivers/pci/pci-aardvark.c
> index b4e1b602405f..3b9309f52c57 100644
> --- a/drivers/pci/pci-aardvark.c
> +++ b/drivers/pci/pci-aardvark.c
> @@ -105,6 +105,7 @@
>   #define     LTSSM_SHIFT				24
>   #define     LTSSM_MASK				0x3f
>   #define     LTSSM_L0				0x10
> +#define VENDOR_ID_REG				(LMI_BASE_ADDR + 0x44)
>   
>   /* PCIe core controller registers */
>   #define CTRL_CORE_BASE_ADDR			0x18000
> @@ -529,6 +530,15 @@ static int pcie_advk_setup_hw(struct pcie_advk *pcie)
>   	reg |= (IS_RC_MSK << IS_RC_SHIFT);
>   	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
>   
> +	/*
> +	 * Replace incorrect PCI vendor id value 0x1b4b by correct value 0x11ab.
> +	 * VENDOR_ID_REG contains vendor id in low 16 bits and subsystem vendor
> +	 * id in high 16 bits. Updating this register changes readback value of
> +	 * read-only vendor id bits in PCIE_CORE_DEV_ID_REG register. Workaround
> +	 * for erratum 4.1: "The value of device and vendor ID is incorrect".
> +	 */
> +	advk_writel(pcie, 0x11ab11ab, VENDOR_ID_REG);
> +
>   	/* Set Advanced Error Capabilities and Control PF0 register */
>   	reg = PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX |
>   		PCIE_CORE_ERR_CAPCTL_ECRC_CHK_TX_EN |
> 

Reviewed-by: Stefan Roese <sr at denx.de>

Thanks,
Stefan