[PATCH 1/1][U/OEM-5.6] PCI: vmd: Enable ASPM if BIOS requests it

Colin Ian King colin.king at canonical.com
Fri Jul 31 08:00:33 UTC 2020


On 30/07/2020 11:34, You-Sheng Yang wrote:
> From: Jon Derrick <jonathan.derrick at intel.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1889384
> 
> VMD domains are not ACPI-managed devices and do not have the necessary
> ACPI hooks to enable ASPM. However if the BIOS has requested ASPM
> enablement, we should try to honor that request regardless. This patch
> adds the ASPM support to VMD child devices if requested by the FADT
> table.
> 
> Signed-off-by: Jon Derrick <jonathan.derrick at intel.com>
> (cherry picked from
> https://lore.kernel.org/linux-pci/20200728161321.38229-1-jonathan.derrick@intel.com/)
> Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.com>
> ---
>  drivers/pci/controller/vmd.c |  9 ++++++++-
>  drivers/pci/pcie/aspm.c      | 19 ++-----------------
>  include/linux/pci.h          | 17 +++++++++++++++++
>  3 files changed, 27 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 9a64cf90c291..60a9373d3360 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -14,6 +14,7 @@
>  #include <linux/srcu.h>
>  #include <linux/rculist.h>
>  #include <linux/rcupdate.h>
> +#include <linux/acpi.h>
>  
>  #include <asm/irqdomain.h>
>  #include <asm/device.h>
> @@ -574,8 +575,14 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  	 * and will fail pcie_bus_configure_settings() early. It can instead be
>  	 * run on each of the real root ports.
>  	 */
> -	list_for_each_entry(child, &vmd->bus->children, node)
> +	list_for_each_entry(child, &vmd->bus->children, node) {
> +#if IS_ENABLED(CONFIG_PCIEASPM)
> +		if (!(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM))
> +			pcie_config_aspm_link(child->self->link_state,
> +					      ASPM_STATE_ALL);
> +#endif
>  		pcie_bus_configure_settings(child);
> +	}
>  
>  	pci_bus_add_devices(vmd->bus);
>  
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index b17e5ffd31b1..23a3fc82364f 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -25,22 +25,6 @@
>  #endif
>  #define MODULE_PARAM_PREFIX "pcie_aspm."
>  
> -/* Note: those are not register definitions */
> -#define ASPM_STATE_L0S_UP	(1)	/* Upstream direction L0s state */
> -#define ASPM_STATE_L0S_DW	(2)	/* Downstream direction L0s state */
> -#define ASPM_STATE_L1		(4)	/* L1 state */
> -#define ASPM_STATE_L1_1		(8)	/* ASPM L1.1 state */
> -#define ASPM_STATE_L1_2		(0x10)	/* ASPM L1.2 state */
> -#define ASPM_STATE_L1_1_PCIPM	(0x20)	/* PCI PM L1.1 state */
> -#define ASPM_STATE_L1_2_PCIPM	(0x40)	/* PCI PM L1.2 state */
> -#define ASPM_STATE_L1_SS_PCIPM	(ASPM_STATE_L1_1_PCIPM | ASPM_STATE_L1_2_PCIPM)
> -#define ASPM_STATE_L1_2_MASK	(ASPM_STATE_L1_2 | ASPM_STATE_L1_2_PCIPM)
> -#define ASPM_STATE_L1SS		(ASPM_STATE_L1_1 | ASPM_STATE_L1_1_PCIPM |\
> -				 ASPM_STATE_L1_2_MASK)
> -#define ASPM_STATE_L0S		(ASPM_STATE_L0S_UP | ASPM_STATE_L0S_DW)
> -#define ASPM_STATE_ALL		(ASPM_STATE_L0S | ASPM_STATE_L1 |	\
> -				 ASPM_STATE_L1SS)
> -
>  struct aspm_latency {
>  	u32 l0s;			/* L0s latency (nsec) */
>  	u32 l1;				/* L1 latency (nsec) */
> @@ -748,7 +732,7 @@ static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
>  					   PCI_EXP_LNKCTL_ASPMC, val);
>  }
>  
> -static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
> +void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>  {
>  	u32 upstream = 0, dwstream = 0;
>  	struct pci_dev *child = link->downstream, *parent = link->pdev;
> @@ -798,6 +782,7 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>  
>  	link->aspm_enabled = state;
>  }
> +EXPORT_SYMBOL_GPL(pcie_config_aspm_link);
>  
>  static void pcie_config_aspm_path(struct pcie_link_state *link)
>  {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 34c1c4f45288..ec0a8b7a55f8 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -377,6 +377,22 @@ struct pci_dev {
>  	unsigned int	d3cold_delay;	/* D3cold->D0 transition time in ms */
>  
>  #ifdef CONFIG_PCIEASPM
> +/* Note: those are not register definitions */
> +#define ASPM_STATE_L0S_UP	(1)	/* Upstream direction L0s state */
> +#define ASPM_STATE_L0S_DW	(2)	/* Downstream direction L0s state */
> +#define ASPM_STATE_L1		(4)	/* L1 state */
> +#define ASPM_STATE_L1_1		(8)	/* ASPM L1.1 state */
> +#define ASPM_STATE_L1_2		(0x10)	/* ASPM L1.2 state */
> +#define ASPM_STATE_L1_1_PCIPM	(0x20)	/* PCI PM L1.1 state */
> +#define ASPM_STATE_L1_2_PCIPM	(0x40)	/* PCI PM L1.2 state */
> +#define ASPM_STATE_L1_SS_PCIPM	(ASPM_STATE_L1_1_PCIPM | ASPM_STATE_L1_2_PCIPM)
> +#define ASPM_STATE_L1_2_MASK	(ASPM_STATE_L1_2 | ASPM_STATE_L1_2_PCIPM)
> +#define ASPM_STATE_L1SS		(ASPM_STATE_L1_1 | ASPM_STATE_L1_1_PCIPM |\
> +				 ASPM_STATE_L1_2_MASK)
> +#define ASPM_STATE_L0S		(ASPM_STATE_L0S_UP | ASPM_STATE_L0S_DW)
> +#define ASPM_STATE_ALL		(ASPM_STATE_L0S | ASPM_STATE_L1 |	\
> +				 ASPM_STATE_L1SS)
> +
>  	struct pcie_link_state	*link_state;	/* ASPM link state */
>  	unsigned int	ltr_path:1;	/* Latency Tolerance Reporting
>  					   supported from root to here */
> @@ -1570,6 +1586,7 @@ extern bool pcie_ports_native;
>  #define PCIE_LINK_STATE_L1_2_PCIPM	BIT(6)
>  
>  #ifdef CONFIG_PCIEASPM
> +void pcie_config_aspm_link(struct pcie_link_state *link, u32 state);
>  int pci_disable_link_state(struct pci_dev *pdev, int state);
>  int pci_disable_link_state_locked(struct pci_dev *pdev, int state);
>  void pcie_no_aspm(void);
> 

The patch originated from:
https://lore.kernel.org/linux-pci/20200728161321.38229-1-jonathan.derrick@intel.com/
- it is labeled as a RFC (request for comment). Also it contains the
text after the SoBs:


"Hi,

My knowledge on these kinds of power modes is limited, and we are having
trouble bringing the Root Port child device out of L1 with this patch.

Can you help me understand the correct flow for bringing the Root Port
device out of L1 with kernel flow, and what I might be missing here?"

..this makes me concerned that this need some time to be properly
reviewed.  As it stands, my knowledge of ASPM is that the BIOS can lie
about ASPM being allowed, so I'm concerned about power state regressions
with this.

Colin



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