Re: [PATCH v2 2/2] PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 10/10/23 17:59, Manivannan Sadhasivam wrote:
> ASPM is supported by Qcom host controllers/bridges on most of the recent
> platforms and so the devices tested so far. But for enabling ASPM by
> default (without Kconfig/cmdline/sysfs), BIOS has to enable ASPM on both
> host bridge and downstream devices during boot. Unfortunately, none of the
> BIOS available on Qcom platforms enables ASPM. Due to this, the platforms
> making use of Qcom SoCs draw high power during runtime.
> 
> To fix this power issue, users/distros have to enable ASPM using configs
> such as (Kconfig/cmdline/sysfs) or the BIOS has to start enabling ASPM.
> The latter may happen in the future, but that won't address the issue on
> current platforms. Also, asking users/distros to enable a feature to get
> the power management right would provide an unpleasant out-of-the-box
> experience.
> 
> So the apt solution is to enable ASPM in the controller driver itself. And
> this is being accomplished by calling pci_enable_link_state() in the newly
> introduced host_post_init() callback for all the devices connected to the
> bus. This function enables all supported link low power states for both
> host bridge and the downstream devices.
> 
> Due to limited testing, ASPM is only enabled for platforms making use of
> ops_1_9_0 callbacks.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
[...]

> +static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata)
> +{
> +	/* Downstream devices need to be in D0 state before enabling PCI PM substates */
> +	pci_set_power_state(pdev, PCI_D0);
> +	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
Do we not care about retval here?

> +
> +	return 0;
> +}
> +
> +static void qcom_pcie_host_post_init_2_7_0(struct qcom_pcie *pcie)
post_init_enable_aspm?

Konrad