linux-kernel - Re: [PATCH v3 1/4] pci: add pci_ioremap_wc

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Message-ID: <20150520210234.GD32152@google.com>
Date:	Wed, 20 May 2015 16:02:34 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
Cc:	mst@...hat.com, plagnioj@...osoft.com, tomi.valkeinen@...com,
	linux-fbdev@...r.kernel.org, luto@...capital.net,
	cocci@...teme.lip6.fr, "Luis R. Rodriguez" <mcgrof@...e.com>,
	Toshi Kani <toshi.kani@...com>,
	Suresh Siddha <sbsiddha@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juergen Gross <jgross@...e.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Dave Airlie <airlied@...hat.com>,
	Antonino Daplas <adaplas@...il.com>,
	Ville Syrjälä <syrjala@....fi>,
	Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
	Borislav Petkov <bp@...e.de>, Davidlohr Bueso <dbueso@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] pci: add pci_ioremap_wc_bar()

On Tue, Apr 21, 2015 at 01:20:31PM -0700, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@...e.com>
> 
> This lets drivers take advantage of PAT when available. This
> should help with the transition of converting video drivers over
> to ioremap_wc() to help with the goal of eventually using
> _PAGE_CACHE_UC over _PAGE_CACHE_UC_MINUS on x86 on
> ioremap_nocache() (de33c442e titled "x86 PAT: fix performance
> drop for glx, use UC minus for ioremap(), ioremap_nocache() and
> pci_mmap_page_range()")
> 
> Cc: Toshi Kani <toshi.kani@...com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Suresh Siddha <sbsiddha@...il.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Dave Airlie <airlied@...hat.com>
> Cc: Antonino Daplas <adaplas@...il.com>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: Ville Syrjälä <syrjala@....fi>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Davidlohr Bueso <dbueso@...e.de>
> Cc: linux-fbdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>

I don't have any objection to this, and I can apply the follow-on patches
as well, given the appropriate acks and prerequisite patches (ioremap_wc()
implementation).

> ---
>  drivers/pci/pci.c   | 14 ++++++++++++++
>  include/linux/pci.h |  1 +
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 687af72..fd14f10 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -138,6 +138,20 @@ void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar)
>  	return ioremap_nocache(res->start, resource_size(res));
>  }
>  EXPORT_SYMBOL_GPL(pci_ioremap_bar);
> +
> +void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar)
> +{
> +	/*
> +	 * Make sure the BAR is actually a memory resource, not an IO resource
> +	 */
> +	if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) {
> +		WARN_ON(1);
> +		return NULL;
> +	}
> +	return ioremap_wc(pci_resource_start(pdev, bar),
> +			  pci_resource_len(pdev, bar));
> +}
> +EXPORT_SYMBOL_GPL(pci_ioremap_wc_bar);
>  #endif
>  
>  #define PCI_FIND_CAP_TTL	48
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index bc50bb0..490ca41 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1667,6 +1667,7 @@ static inline void pci_mmcfg_late_init(void) { }
>  int pci_ext_cfg_avail(void);
>  
>  void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar);
> +void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar);
>  
>  #ifdef CONFIG_PCI_IOV
>  int pci_iov_virtfn_bus(struct pci_dev *dev, int id);
> -- 
> 2.3.2.209.gd67f9d5.dirty
> 
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