linux-kernel - Re: [PATCH v2 6/6] usb: host: ohci-exynos: Use devm_ioremap_resource instead of devm

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Date:	Wed, 4 Jun 2014 15:41:20 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Linux USB Mailing List <linux-usb@...r.kernel.org>
Cc:	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	linux-tegra <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Stephen Warren <swarren@...dotorg.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexander Shiyan <shc_work@...l.ru>,
	Vivek Gautam <gautam.vivek@...sung.com>
Subject: Re: [PATCH v2 6/6] usb: host: ohci-exynos: Use devm_ioremap_resource
 instead of devm_ioremap

Hi,


On Sat, May 10, 2014 at 5:30 PM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
> Using devm_ioremap_resource() API should actually be preferred over
> devm_ioremap(), since the former request the mem region first and then
> gives back the ioremap'ed memory pointer.
> devm_ioremap_resource() calls request_mem_region(), therby preventing
> other drivers to make any overlapping call to the same region.
>
> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>

Although this patch and rest in the series are merged.
But i have got a doubt, so making this thread alive.

> ---
>  drivers/usb/host/ohci-exynos.c |    7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/host/ohci-exynos.c b/drivers/usb/host/ohci-exynos.c
> index 9cf80cb..dec691d 100644
> --- a/drivers/usb/host/ohci-exynos.c
> +++ b/drivers/usb/host/ohci-exynos.c
> @@ -120,10 +120,9 @@ skip_phy:
>
>         hcd->rsrc_start = res->start;
>         hcd->rsrc_len = resource_size(res);
> -       hcd->regs = devm_ioremap(&pdev->dev, res->start, hcd->rsrc_len);
> -       if (!hcd->regs) {
> -               dev_err(&pdev->dev, "Failed to remap I/O memory\n");
> -               err = -ENOMEM;
> +       hcd->regs = devm_ioremap_resource(&pdev->dev, res);

Here, we replaced devm_ioremap() call with devm_ioremap_resource(),
which internally
requests the memory region and then does a "devm_ioremap()" or
"devm_ioremap_nocache()"
based on the check for IORESOURCE_CACHEABLE flag.

But this flag is not set for the resource of this device.
So should we be explicitly setting the flag in driver ?

The query goes for other patches too in this series, wherein
devm_ioremap() call is replaced with devm_ioremap_resource().

[snip]


-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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