[PATCH v2 1/7] arm: a37xx: pci: Don't put link into LTSSM Recovery state during probe

[Stefan Roese]

On 26.05.21 17:59, Pali Rohár wrote:
> During our debugging of the Aardvark driver in Linux we have discovered
> that the PCIE_CORE_LINK_CTRL_STAT_REG register in fact controls standard
> PCIe Link Control Register for PCIe Root Bridge. This led us to discover
> that the name of the PCIE_CORE_LINK_TRAINING macro and the corresponding
> comment by this macro's usage is misleading; this bit in fact controls
> Retrain Link, which, according to PCIe base spec is defined as:
> 
>    A write of 1b to this bit initiates Link retraining by directing the
>    Physical Layer LTSSM to the Recovery state. If the LTSSM is already in
>    Recovery or Configuration, re-entering Recovery is permitted but not
>    required.
> 
> Entering Recovery state is normally done from LTSSM L0, L0s and L1 states.
> But since the pci-aardvark.c driver enables Link Training just a few lines
> above, the controller is not in L0 ready state yet. So setting aardvark bit
> PCIE_CORE_LINK_TRAINING does not actually enter Recovery state at this
> place.
> 
> Moreover, trying to enter LTSSM Recovery state without other configuration
> is causing issues for some cards (e.g. Atheros AR9xxx and QCA9xxx). Since
> Recovery state is not entered, these issues are not triggered.
> 
> Remove code which tries to enter LTSSM Recovery state completely.
> 
> Signed-off-by: Pali Rohár <pali at kernel.org>
> Reviewed-by: Marek Behún <marek.behun at nic.cz>

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

Thanks,
Stefan

> ---
>   drivers/pci/pci-aardvark.c | 5 -----
>   1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/pci/pci-aardvark.c b/drivers/pci/pci-aardvark.c
> index c43d4f309b19..06c567e236f9 100644
> --- a/drivers/pci/pci-aardvark.c
> +++ b/drivers/pci/pci-aardvark.c
> @@ -613,11 +613,6 @@ static int pcie_advk_setup_hw(struct pcie_advk *pcie)
>   	reg |= PIO_CTRL_ADDR_WIN_DISABLE;
>   	advk_writel(pcie, reg, PIO_CTRL);
>   
> -	/* Start link training */
> -	reg = advk_readl(pcie, PCIE_CORE_LINK_CTRL_STAT_REG);
> -	reg |= PCIE_CORE_LINK_TRAINING;
> -	advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG);
> -
>   	/* Wait for PCIe link up */
>   	if (pcie_advk_wait_for_link(pcie))
>   		return -ENXIO;
> 


Viele Grüße,
Stefan

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