linux-kernel - Re: [PATCH] pciehp: Add pciehp

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Date:	Fri, 22 Mar 2013 10:20:43 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Michal Marek <mmarek@...e.cz>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	Takashi Iwai <tiwai@...e.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Oliver Neukum <oneukum@...e.de>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pciehp: Add pciehp_surprise module option

On Fri, 2013-03-22 at 17:15 +0100, Michal Marek wrote:
> On 20.3.2013 20:08, Takashi Iwai wrote:
> > At Wed, 20 Mar 2013 12:09:13 -0600,
> > Alex Williamson wrote:
> >>
> >> On Wed, 2013-03-20 at 15:02 +0100, Takashi Iwai wrote:
> >>> We encountered a problem that on some HP machines the Realtek PCI-e
> >>> card reader device appears only when you inserted a card before the
> >>> cold boot.  While debugging, it turned out that the device is actually
> >>> handled via PCI-e hotplug in some level.  The device sends a presence
> >>> change notification, and pciehp receives it, but it's ignored because
> >>> of lack of the hotplug surprise (PCI_EXP_SLTCAP_HPS) capability bit.
> >>> Once when this check passes, everything starts working -- the device
> >>> appears upon plugging the card properly.
> >>>
> >>> There are a few other bug reports indicating the similar problems
> >>> (e.g. on recent Dell laptops), and I guess the culprit is same.
> >>>
> >>> This patch adds a new module option, pciehp_surprise, to pciehp as a
> >>> workaround.  When pciehp_surprise=1 is given, pciehp handles the
> >>> presence change as the device on/off as if PCI_EXP_SLTCAP_HPS is set.
> >>> Unless it's set explicitly, there is no impact on the existing
> >>> behavior.
> >>>
> >>> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> >>> ---
> >>>  drivers/pci/hotplug/pciehp.h      | 3 ++-
> >>>  drivers/pci/hotplug/pciehp_core.c | 3 +++
> >>>  2 files changed, 5 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
> >>> index 2c113de..314f3be 100644
> >>> --- a/drivers/pci/hotplug/pciehp.h
> >>> +++ b/drivers/pci/hotplug/pciehp.h
> >>> @@ -44,6 +44,7 @@ extern bool pciehp_poll_mode;
> >>>  extern int pciehp_poll_time;
> >>>  extern bool pciehp_debug;
> >>>  extern bool pciehp_force;
> >>> +extern bool pciehp_surprise;
> >>>  
> >>>  #define dbg(format, arg...)						\
> >>>  do {									\
> >>> @@ -122,7 +123,7 @@ struct controller {
> >>>  #define MRL_SENS(ctrl)		((ctrl)->slot_cap & PCI_EXP_SLTCAP_MRLSP)
> >>>  #define ATTN_LED(ctrl)		((ctrl)->slot_cap & PCI_EXP_SLTCAP_AIP)
> >>>  #define PWR_LED(ctrl)		((ctrl)->slot_cap & PCI_EXP_SLTCAP_PIP)
> >>> -#define HP_SUPR_RM(ctrl)	((ctrl)->slot_cap & PCI_EXP_SLTCAP_HPS)
> >>> +#define HP_SUPR_RM(ctrl)	(pciehp_surprise || ((ctrl)->slot_cap & PCI_EXP_SLTCAP_HPS))
> >>>  #define EMI(ctrl)		((ctrl)->slot_cap & PCI_EXP_SLTCAP_EIP)
> >>>  #define NO_CMD_CMPL(ctrl)	((ctrl)->slot_cap & PCI_EXP_SLTCAP_NCCS)
> >>>  #define PSN(ctrl)		((ctrl)->slot_cap >> 19)
> >>> diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
> >>> index 7d72c5e..c3a574e 100644
> >>> --- a/drivers/pci/hotplug/pciehp_core.c
> >>> +++ b/drivers/pci/hotplug/pciehp_core.c
> >>> @@ -42,6 +42,7 @@ bool pciehp_debug;
> >>>  bool pciehp_poll_mode;
> >>>  int pciehp_poll_time;
> >>>  bool pciehp_force;
> >>> +bool pciehp_surprise;
> >>>  
> >>>  #define DRIVER_VERSION	"0.4"
> >>>  #define DRIVER_AUTHOR	"Dan Zink <dan.zink@...paq.com>, Greg Kroah-Hartman <greg@...ah.com>, Dely Sy <dely.l.sy@...el.com>"
> >>> @@ -55,10 +56,12 @@ module_param(pciehp_debug, bool, 0644);
> >>>  module_param(pciehp_poll_mode, bool, 0644);
> >>>  module_param(pciehp_poll_time, int, 0644);
> >>>  module_param(pciehp_force, bool, 0644);
> >>> +module_param(pciehp_surprise, bool, 0644);
> >>>  MODULE_PARM_DESC(pciehp_debug, "Debugging mode enabled or not");
> >>>  MODULE_PARM_DESC(pciehp_poll_mode, "Using polling mechanism for hot-plug events or not");
> >>>  MODULE_PARM_DESC(pciehp_poll_time, "Polling mechanism frequency, in seconds");
> >>>  MODULE_PARM_DESC(pciehp_force, "Force pciehp, even if OSHP is missing");
> >>> +MODULE_PARM_DESC(pciehp_surprise, "Force to set hotplug-surprise capability");
> >>>  
> >>>  #define PCIE_MODULE_NAME "pciehp"
> >>>  
> >>
> >> Please no.  Can we quirk just the device with the problem?
> > 
> > It'd be good to have a static quirk in the end, yes.
> 
> Alex, Matthew, would it work for you to have this debug / band-aid
> option _and_ have a list of either machines' dmi strings that have this
> problem, or devices' PCI IDs (*), and enable the surprise event handling
> for such machines / devices automatically?  The option would be still
> useful for debugging, to be able to easily find out if given machine has
> this problem and needs to be added to the quirk list.
> 
> (*) It would probably make more sense to have a list of dmi strings,
> because it's the PCIe controller that does not set the capability bit
> when it should. The device (Realtek card reader in this case) seems to
> behave correctly. The machines in question have been laptops or
> all-in-one PCs so far, so there should be no problem with dmi matches.

Yep, I think that makes sense, leave the global option for debugging but
fix individual known broken devices through dmi quirks.  Thanks,

Alex

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