[PATCH v2] PCI: rockchip: Add quirk to disable RC's ASPM L0s

[Bjorn Helgaas]

On Mon, Dec 12, 2016 at 07:51:27PM +0800, Shawn Lin wrote:
> Rockchip's RC outputs 100MHz reference clock but there are
> two methods for PHY to generate it.
> 
> (1)One of them is to use system PLL to generate 100MHz clock and
> the PHY will relock it and filter signal noise then outputs the
> reference clock.
> 
> (2)Another way is to share Soc's 24MHZ crystal oscillator with
> PHY and force PHY's DLL to generate 100MHz internally.
> 
> When using case(2), the exit from L0s doesn't work fine occasionally
> due to the broken design of RC receiver's logical circuit. So even if
> we use extended-synch, it still fails for PHY to relock the bits from
> FTS sometimes. This will hang the system.
> 
> Maybe we could argue that why not use case(1) to avoid it? The reason
> is that as we could see the reference clock is derived from system PLL
> and the path from it to PHY isn't so clean which means there are some
> noise introduced by power-domain and other buses can't be filterd out
> by PHY and we could see noise from the frequency spectrum by
> oscilloscope. This makes the TX compatibility test a little difficult
> to pass the spec. So case(1) and case(2) are both used indeed now. If
> using case(2), we should disable RC's L0s support, and that is why we
> need this property to indicate this quirk.
> 
> Also after checking quirk.c, I noticed there is already a quirk for
> disabling L0s unconditionally, quirk_disable_aspm_l0s. But obviously we
> shouldn't do that as mentioned above that case(1) could still works fine
> with L0s.
> 
> Reported-by: Jeffy Chen <jeffy.chen at rock-chips.com>
> Cc: Brian Norris <briannorris at chromium.org>
> Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
> 
> ---
> 
> Changes in v2:
> - drop the quirk prefix
> 
>  Documentation/devicetree/bindings/pci/rockchip-pcie.txt | 2 ++
>  drivers/pci/host/pcie-rockchip.c                        | 9 +++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/rockchip-pcie.txt b/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> index 71aeda1..1453a73 100644
> --- a/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> +++ b/Documentation/devicetree/bindings/pci/rockchip-pcie.txt
> @@ -43,6 +43,8 @@ Required properties:
>  - interrupt-map-mask and interrupt-map: standard PCI properties
>  
>  Optional Property:
> +- aspm-no-l0s: RC won't support ASPM L0s. This property is needed if
> +	using 24MHz OSC for RC's PHY.
>  - ep-gpios: contain the entry for pre-reset gpio
>  - num-lanes: number of lanes to use
>  - vpcie3v3-supply: The phandle to the 3.3v regulator to use for PCIe.
> diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
> index f2dca7b..35988fc 100644
> --- a/drivers/pci/host/pcie-rockchip.c
> +++ b/drivers/pci/host/pcie-rockchip.c
> @@ -140,6 +140,8 @@
>  #define   PCIE_RC_CONFIG_DCR_CSPL_SHIFT		18
>  #define   PCIE_RC_CONFIG_DCR_CSPL_LIMIT		0xff
>  #define   PCIE_RC_CONFIG_DCR_CPLS_SHIFT		26
> +#define PCIE_RC_CONFIG_LINK_CAP		(PCIE_RC_CONFIG_BASE + 0xcc)
> +#define   PCIE_RC_CONFIG_LINK_CAP_L0S		BIT(10)
>  #define PCIE_RC_CONFIG_LCS		(PCIE_RC_CONFIG_BASE + 0xd0)
>  #define PCIE_RC_CONFIG_L1_SUBSTATE_CTRL2 (PCIE_RC_CONFIG_BASE + 0x90c)
>  #define PCIE_RC_CONFIG_THP_CAP		(PCIE_RC_CONFIG_BASE + 0x274)
> @@ -653,6 +655,13 @@ static int rockchip_pcie_init_port(struct rockchip_pcie *rockchip)
>  	status &= ~PCIE_RC_CONFIG_THP_CAP_NEXT_MASK;
>  	rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_THP_CAP);
>  
> +	/* Clear L0s from RC's link cap */
> +	if (of_property_read_bool(dev->of_node, "apsm-no-l0s")) {

Did you test this?  This string ("apsm-no-l0s") doesn't match the
"aspm-no-l0s" documented above.  The current tree doesn't contain either
string in any DTS.

> +		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_LINK_CAP);
> +		status &= ~PCIE_RC_CONFIG_LINK_CAP_L0S;
> +		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_LINK_CAP);
> +	}
> +
>  	rockchip_pcie_write(rockchip, 0x0, PCIE_RC_BAR_CONF);
>  
>  	rockchip_pcie_write(rockchip,
> -- 
> 1.9.1
> 
> 
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