linux-kernel - Re: [PATCH v3 2/3] MIPS: Add CDMM bus support

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Date:	Wed, 25 Mar 2015 23:03:39 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] MIPS: Add CDMM bus support

On Wed, Mar 25, 2015 at 03:39:50PM +0000, James Hogan wrote:
> Add MIPS Common Device Memory Map (CDMM) support in the form of a bus in
> the standard Linux device model. Each device attached via CDMM is
> discoverable via an 8-bit type identifier and may contain a number of
> blocks of memory mapped registers in the CDMM region. IRQs are expected
> to be handled separately.
> 
> Due to the per-cpu (per-VPE for MT cores) nature of the CDMM devices,
> all the driver callbacks take place from workqueues which are run on the
> right CPU for the device in question, so that the driver doesn't need to
> be as concerned about which CPU it is running on. Callbacks also exist
> for when CPUs are taken offline, so that any per-CPU resources used by
> the driver can be disabled so they don't get forcefully migrated. CDMM
> devices are created as children of the CPU device they are attached to.
> 
> Any existing CDMM configuration by the bootloader will be inherited,
> however platforms wishing to enable CDMM should implement the weak
> mips_cdmm_phys_base() function (see asm/cdmm.h) so that the bus driver
> knows where it should put the CDMM region in the physical address space
> if the bootloader hasn't already enabled it.
> 
> A mips_cdmm_early_probe() function is also provided to allow early boot
> or particularly low level code to set up the CDMM region and probe for a
> specific device type, for example early console or KGDB IO drivers for
> the EJTAG Fast Debug Channel (FDC) CDMM device.
> 
> Signed-off-by: James Hogan <james.hogan@...tec.com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-mips@...ux-mips.org
> ---
> Changes in v3:
> - Convert to use dev_groups rather than dev_attrs (GregKH).
> - Rename mips_cdmm_attr_func() macro to CDMM_ATTR for consistency with
>   other similar macro names I've seen around the kernel.
> - Add modalias attribute.
> 
> Changes in v2:
> - Fix some checkpatch errors.
> - Correct CDMM name in various places. It is "Common Device Memory Map",
>   rather than "Common Device Mapped Memory" (which for some reason had
>   got stuck in my head).
> ---
>  arch/mips/include/asm/cdmm.h      |  87 +++++
>  drivers/bus/Kconfig               |  13 +
>  drivers/bus/Makefile              |   1 +
>  drivers/bus/mips_cdmm.c           | 716 ++++++++++++++++++++++++++++++++++++++
>  include/linux/mod_devicetable.h   |   8 +
>  scripts/mod/devicetable-offsets.c |   3 +
>  scripts/mod/file2alias.c          |  16 +
>  7 files changed, 844 insertions(+)
>  create mode 100644 arch/mips/include/asm/cdmm.h
>  create mode 100644 drivers/bus/mips_cdmm.c

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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