linux-kernel - Re: [RFC] PCIE ASPM support

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Date:	Tue, 08 Jan 2008 09:35:42 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	michael@...erman.id.au
Cc:	lkml <linux-kernel@...r.kernel.org>,
	linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	Greg KH <greg@...ah.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: Re: [RFC] PCIE ASPM support


On Tue, 2008-01-08 at 09:02 +1100, Michael Ellerman wrote:
> On Thu, 2008-01-03 at 14:15 +0800, Shaohua Li wrote:
> > PCI Express ASPM defines a protocol for PCI Express components in the D0
> > state to reduce Link power by placing their Links into a low power state
> > and instructing the other end of the Link to do likewise. This
> > capability allows hardware-autonomous, dynamic Link power reduction
> > beyond what is achievable by software-only controlled power management.
> > However, The device should be configured by software appropriately.
> > Enabling ASPM will save power, but will introduce device latency.
> > 
> > This patch adds ASPM support in Linux. It introduces a global policy for
> > ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control
> > it. The interface can be used as a boot option too. Currently we have
> > below setting:
> > 	-default, BIOS default setting
> > 	-powersave, highest power saving mode, enable all available ASPM state
> > and clock power management
> > 	-performance, highest performance, disable ASPM and clock power
> > management
> > By default, the 'default' policy is used currently.
> > 
> > In my test, power difference between powersave mode and performance mode
> > is about 1.3w in a system with 3 PCIE links.
> > 
> > please review, any comments will be appreciated.
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@...el.com>
> 
> Minor nit, but you do a lot of these:
> 
> +	return ((struct link_state *)pdev->link_state)->bios_aspm_state;
> +	return ((struct link_state *)pdev->link_state)->bios_clk_state;
> +	((struct link_state*)pdev->link_state)->clk_pm_enabled = !!enable;
> +	((struct link_state*)pdev->link_state)->clk_pm_capable = capable;
> +	((struct link_state*)pdev->link_state)->clk_pm_enabled = enabled;
> +	((struct link_state*)pdev->link_state)->bios_clk_state = enabled;
> +	((struct link_state *)pdev->link_state)->enabled_state = state;
> +	if (((struct link_state *)pdev->link_state)->support_state == 0)
> +	if (((struct link_state *)pdev->link_state)->enabled_state == state)
> +	((struct link_state *)pdev->link_state)->enabled_state);
Thanks for your time. I'll fix in next release.

Thanks,
Shaohua

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