[PATCH] arm64: a37xx: pci: Disable link training when unloading driver

[Stefan Roese]

On 22.09.20 13:21, Pali Rohár wrote:
> As required by PCI Express spec a delay for at least 100ms after
> de-asserting PERST# signal is needed before link training is enabled.
> 
> Linux kernels prior to 5.8 version do not automatically disable link
> training before de-asserting PERST# signal, therefore this requirement is
> not fulfilled.
> 
> Above requirement is needed for proper detection of some Compex PCIe WiFi
> cards. Otherwise Linux kernel cannot detect it.
> 
> To allow using those PCIe cards with older Linux kernel versions booted by
> U-Boot compiled with U-Boot a37xx pci driver, disable link training in
> U-Boot when unloading this pci driver.
> 
> Thanks to DM_FLAG_OS_PREPARE flag, U-Boot automatically unload this driver
> when booting Linux kernel.
> 
> Signed-off-by: Pali Rohár <pali at kernel.org>

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

Thanks,
Stefan

> ---
>   drivers/pci/pci-aardvark.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/pci-aardvark.c b/drivers/pci/pci-aardvark.c
> index b2c417701f..babb84ca93 100644
> --- a/drivers/pci/pci-aardvark.c
> +++ b/drivers/pci/pci-aardvark.c
> @@ -647,10 +647,15 @@ static int pcie_advk_probe(struct udevice *dev)
>   static int pcie_advk_remove(struct udevice *dev)
>   {
>   	struct pcie_advk *pcie = dev_get_priv(dev);
> +	u32 reg;
>   
>   	if (dm_gpio_is_valid(&pcie->reset_gpio))
>   		dm_gpio_set_value(&pcie->reset_gpio, 1);
>   
> +	reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG);
> +	reg &= ~LINK_TRAINING_EN;
> +	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
> +
>   	return 0;
>   }
>   
> 


Viele Grüße,
Stefan

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