From: khalasa@piap•pl (Krzysztof Hałasa)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 3/7] usb: gadget: pxa25x_udc: use readl/writel for mmio
Date: Mon, 15 Feb 2016 08:33:37 +0100 [thread overview]
Message-ID: <m3a8n2bf72.fsf@t19.piap.pl> (raw)
In-Reply-To: <2202960.HHsdV23CYi@wuerfel> (Arnd Bergmann's message of "Fri, 29 Jan 2016 18:06:58 +0100")
Arnd Bergmann <arnd@arndb•de> writes:
>> Anyway, I think readl()/writel() do the right thing: in BE mode they
>> swap PCI accesses and don't swap normal registers, in LE mode nothing is
>> swapped.
>
> This seems to be true when CONFIG_IXP4XX_INDIRECT_PCI is set, but
> not otherwise. For the indirect variant, writel() is a __raw_writel()
> without barrier or byteswap on non-PCI memory, while with that
> option disabled, we use the standard implementation that has both
> a byteswap and a barrier.
>
> According to your description, that would mean the version without
> indirect PCI access is broken and it appears to have been that way
> since before the start of git history in 2.6.12.
>
> It's possible that nobody cared because all drivers for non-PCI
> devices on ixp4xx (the on chip ones) just use __raw_readl or
> direct pointer references.
Well, it is possible. I recall I probably used __raw_* instead of
readl()/writel() in qmgr/npe/Ethernet drivers for this very reason.
I think Direct pointer references are only used for locations in RAM
(DMA buffers), they have their own share of problems because the
peripherals are always big endian.
I think I still have an early IXP425 board with UDC connector so I will
try to dig it up and test this code.
I wonder if we should switch the driver to use __raw_*, too. The problem
is almost nobody uses UDC with this CPU.
--
Krzysztof Halasa
Industrial Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland
next prev parent reply other threads:[~2016-02-15 7:33 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 16:15 [PATCH 0/7] USB changes for rare warnings Arnd Bergmann
2016-01-28 16:17 ` [PATCH 1/7] usb: gadget: pxa25x_udc: move register definitions from arch Arnd Bergmann
2016-01-28 16:17 ` [PATCH 2/7] usb: gadget: pxa25x_udc cleanup Arnd Bergmann
2016-01-29 10:13 ` Robert Jarzmik
2016-01-28 16:17 ` [PATCH 3/7] usb: gadget: pxa25x_udc: use readl/writel for mmio Arnd Bergmann
2016-01-29 10:17 ` Robert Jarzmik
2016-01-29 16:18 ` Krzysztof Hałasa
2016-01-29 17:06 ` Arnd Bergmann
2016-02-15 7:33 ` Krzysztof Hałasa [this message]
2016-02-15 9:33 ` Arnd Bergmann
2016-02-15 13:51 ` Krzysztof Hałasa
2016-02-15 16:12 ` Arnd Bergmann
2016-02-16 9:26 ` Krzysztof Hałasa
2016-02-16 11:26 ` Arnd Bergmann
2016-02-16 13:24 ` Krzysztof Hałasa
2016-02-16 13:55 ` Arnd Bergmann
2016-02-17 8:36 ` Krzysztof Hałasa
2016-02-17 10:36 ` Arnd Bergmann
2016-02-17 16:14 ` Krzysztof Hałasa
2016-02-20 20:54 ` Robert Jarzmik
2016-01-29 18:03 ` Sergei Shtylyov
2016-01-29 21:02 ` Arnd Bergmann
2016-01-29 9:32 ` [PATCH 1/7] usb: gadget: pxa25x_udc: move register definitions from arch Robert Jarzmik
2016-01-29 10:07 ` Arnd Bergmann
2016-01-29 15:26 ` Robert Jarzmik
2016-01-29 15:55 ` Krzysztof Hałasa
2016-02-17 15:08 ` Felipe Balbi
2016-02-17 16:00 ` Arnd Bergmann
2016-01-28 16:20 ` [PATCH 4/7] usb: fsl: drop USB_FSL_MPH_DR_OF Kconfig symbol Arnd Bergmann
2016-01-28 16:23 ` [PATCH 5/7] usb: isp1301-omap: mark power_up as __maybe_unused Arnd Bergmann
2016-01-28 16:23 ` [PATCH 6/7] usb: musb: use %pad format string from dma_addr_t Arnd Bergmann
2016-01-28 17:50 ` Tony Lindgren
2016-01-28 16:23 ` [PATCH 7/7] usb: musb/ux500: remove duplicate check for dma_is_compatible Arnd Bergmann
2016-02-03 18:12 ` [PATCH 0/7] USB changes for rare warnings Felipe Balbi
2016-02-03 19:15 ` Robert Jarzmik
2016-02-03 20:49 ` Arnd Bergmann
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