linux-kernel - Re: Add option to passively listen for PCIE hotplug events

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Message-ID: <49106DD7.9010307@tuffmail.co.uk>
Date:	Tue, 04 Nov 2008 15:44:23 +0000
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Matthew Garrett <mjg59@...f.ucam.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Add option to passively listen for PCIE hotplug events

Matthew Garrett wrote:
> On Tue, Nov 04, 2008 at 03:01:07PM +0000, Alan Jenkins wrote:
>
>   
>> Hey... you're making this conditional on whether a power led is reported
>> present, right?  Are you sure the EeePC doesn't report itself as having
>> a power led?
>>     
>
> Doesn't seem to on the one I was testing, but it's possible. Any chance 
> you could instrument it? There's only a few calls to msleep in 
> pcihp_ctrl.c.
>   

And pciehp_hpc.c!

I instrumented all the delays I could find. hpc_check_lnk_status() was
the only one that came up.  1000ms delay per call, and I get 6 such delays.

The code is saying my hardware lacks "Data Layer Link Active Reporting".



    static int hpc_check_lnk_status(struct controller *ctrl)
    {
        u16 lnk_status;
        int retval = 0;

            /*
             * Data Link Layer Link Active Reporting must be capable for
             * hot-plug capable downstream port. But old controller might
             * not implement it. In this case, we wait for 1000 ms.
             */
            if (ctrl->link_active_reporting){
                    /* Wait for Data Link Layer Link Active bit to be set */
                    pcie_wait_link_active(ctrl);
                    /*
                     * We must wait for 100 ms after the Data Link Layer
                     * Link Active bit reads 1b before initiating a
                     * configuration access to the hot added device.
                     */
                    msleep(100);
            } else {
                    msleep(1000);

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