[PATCH v2 1/2] ARM: EXYNOS: Add USB HOST register definitions

Heiko Stübner heiko at sntech.de
Thu Mar 1 20:15:41 UTC 2012


Am Donnerstag 01 März 2012, 17:10:52 schrieb Sangwook Lee:
> On 1 March 2012 15:24, Heiko Stübner <heiko at sntech.de> wrote:
> > Am Donnerstag, 1. März 2012, 06:38:20 schrieb Jingoo Han:
> > > This patch adds USB HOST register definitions. The definition for
> > > EHCI INSNREG00 regiser and corresponding bit field definitions are
> > > added.
> > > 
> > > Signed-off-by: Sangwook Lee <sangwook.lee at linaro.org>
> > > Signed-off-by: Jingoo Han <jg1.han at samsung.com>
> > > ---
> > > v2: change the definition name from EHCI_ENA_xxx to
> > 
> > EHCI_INSNREG00_ENA_xxx.
> > 
> > > arch/arm/mach-exynos/include/mach/regs-usb-host.h |   24
> > > +++++++++++++++++++++ 1 files changed, 24 insertions(+), 0 deletions(-)
> > > 
> > >  create mode 100644 arch/arm/mach-exynos/include/mach/regs-usb-host.h
> > 
> > Isn't the general idea to depopulate the mach directories and make
> > drivers buildable across architectures?
> > 
> > The definitions are only used in drivers/usb/host/ehci-s5p.c [in the
> > second patch], so there should be no need to add another arch-header and
> > they could
> > simply be included in the driver itself or if necessary a
> > drivers/usb/host/ehci-s5p.h .
> 
>  I found out some code related to this burst function.
> 
>  the snip from ehci-s5pv210.c, 2.6.35 kernel
> 
>         /* Mark hardware accessible again as we are out of D3 state by now
> */
>         set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
> #if defined(CONFIG_ARCH_S5PV210) || defined(CONFIG_ARCH_S5P6450)
>         ehci_writel(ehci, 0x000F0000, (void __iomem *)ehci->caps + 0x90);
> #endif
> 
> #if defined(CONFIG_ARCH_S5PV310)
>         ehci_writel(ehci, 0x03C00000, (void __iomem *)ehci->caps + 0x90);
> #endif
>         if (ehci_readl(ehci, &ehci->regs->configured_flag) == FLAG_CF) {
> 
> From this code, this burst function seems to be depending on CPUs,
> The driver by itself is not good idea because echi-s5p.c will have defined.

The current driver in mainline does not contain these ifdefs and this also 
should not change. What would happen in the code above if ARCH_S5PV210 and 
ARCH_S5PV310 are selected?

As providing support for more than one SoC in a kernel image is one of the 
current targets, architecture dependant stuff like the code above should 
probably be detected at runtime and definitly not compile-time.

> Which is the better place to pus this CPU specific definition either
> drivers/usb/host/ehci-s5p.h is
> or mach/xx.h or  include/linux/usb/xxx.h ?  I am not clear about this.

As I understand it, drivers should be compileable even if the underlying 
architecture is not selected and hence mustn't depend on architecure code.

Use-cases are for example compile-testing all usb-host drivers at once during 
some sort of rework, or the multi-arch kernel mentioned above.

But I really do not see why these defines you're adding cannot simply live 
inside the ehci-s5p.c . For example take a look at 
drivers/usb/gadget/s3c-hsudc.c . This driver also contains its private defines 
without the need for another header.


> > > diff --git a/arch/arm/mach-exynos/include/mach/regs-usb-host.h
> > > b/arch/arm/mach-exynos/include/mach/regs-usb-host.h new file mode
> > > 100644 index 0000000..572b7d4
> > > --- /dev/null
> > > +++ b/arch/arm/mach-exynos/include/mach/regs-usb-host.h
> > > @@ -0,0 +1,24 @@
> > > +/*
> > > + * Copyright (C) 2012 Samsung Electronics Co.Ltd
> > > + *           http://www.samsung.com
> > > + *
> > > + * EXYNOS - USB HOST register definitions
> > > + *
> > > + * This program is free software; you can redistribute it and/or
> > > modify + * it under the terms of the GNU General Public License
> > > version 2 as + * published by the Free Software Foundation.
> > > + */
> > > +
> > > +#ifndef __REGS_USB_HOST_H
> > > +#define __REGS_USB_HOST_H __FILE__
> > > +
> > > +#define EHCI_INSNREG00(base)                 (base + 0x90)
> > > +#define EHCI_INSNREG00_ENA_INCR16            (0x1 << 25)
> > > +#define EHCI_INSNREG00_ENA_INCR8             (0x1 << 24)
> > > +#define EHCI_INSNREG00_ENA_INCR4             (0x1 << 23)
> > > +#define EHCI_INSNREG00_ENA_INCRX_ALIGN               (0x1 << 22)
> > > +#define EHCI_INSNREG00_ENABLE_DMA_BURST      \
> > > +     (EHCI_INSNREG00_ENA_INCR16 | EHCI_INSNREG00_ENA_INCR8 | \
> > > +      EHCI_INSNREG00_ENA_INCR4 | EHCI_INSNREG00_ENA_INCRX_ALIGN)
> > > +
> > > +#endif /* __REGS_USB_HOST_H */
> > 
> > --
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