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Message-ID: <4D127C71.5040301@bluewatersys.com>
Date: Thu, 23 Dec 2010 11:32:17 +1300
From: Ryan Mallon <ryan@...ewatersys.com>
To: Alexey Charkov <alchark@...il.com>
CC: Russell King - ARM Linux <linux@....linux.org.uk>,
linux-arm-kernel@...ts.infradead.org,
vt8500-wm8505-linux-kernel@...glegroups.com,
Eric Miao <eric.y.miao@...il.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Albin Tonnerre <albin.tonnerre@...e-electrons.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6 v10] ARM: Add basic architecture support for VIA/WonderMedia
85xx SoC's
On 12/23/2010 11:02 AM, Alexey Charkov wrote:
> 2010/12/23 Ryan Mallon <ryan@...ewatersys.com>:
>> On 12/23/2010 10:18 AM, Alexey Charkov wrote:
>>> This adds support for the family of Systems-on-Chip produced initially
>>> by VIA and now its subsidiary WonderMedia that have recently become
>>> widespread in lower-end Chinese ARM-based tablets and netbooks.
>>>
>>> Support is included for both VT8500 and WM8505, selectable by a
>>> configuration switch at kernel build time.
>>>
>>> Included are basic machine initialization files, register and
>>> interrupt definitions, support for the on-chip interrupt controller,
>>> high-precision OS timer, GPIO lines, necessary macros for early debug,
>>> pulse-width-modulated outputs control, as well as platform device
>>> configurations for the specific drivers implemented elsewhere.
>>>
>>> Signed-off-by: Alexey Charkov <alchark@...il.com>
>>> ---
>>>
>>> Welcome the jubilee tenth revision of this patch ;-)
>>>
>>> I've tried to incorporate the suggestions by Ryan and Arnd, hope that
>>> there is nothing left out. There was a massive reorganization of code
>>> to remove less-than-obvious magic with MMIO registers and irqs being
>>> held in huge structs, now they are again macro definitions. Those
>>> macros are, however, only included in single isolated files, and
>>> actual values to use are chosen at runtime by calling the respective
>>> routines at machine initialization. There are also stylistic changes
>>> all around, where Ryan suggested.
>>>
>>> As a result, i8042 should again be adjusted a bit to reflect the new
>>> place to find respective register/irq definitions, that one will be
>>> sent in the respective thread shortly.
>>>
>>> Best regards,
>>> Alexey
>>
>> <snip>
>>
>>> --- /dev/null
>>> +++ b/arch/arm/mach-vt8500/devices-vt8500.c
>>> @@ -0,0 +1,117 @@
>>> +/* linux/arch/arm/mach-vt8500/devices-vt8500.c
>>> + *
>>> + * Copyright (C) 2010 Alexey Charkov <alchark@...il.com>
>>> + *
>>> + * This software is licensed under the terms of the GNU General Public
>>> + * License version 2, as published by the Free Software Foundation, and
>>> + * may be copied, distributed, and modified under those terms.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> + * GNU General Public License for more details.
>>> + *
>>> + */
>>> +
>>> +#include <linux/platform_device.h>
>>> +
>>> +#include <mach/vt8500_regs.h>
>>> +#include <mach/vt8500_irqs.h>
>>> +#include <mach/i8042.h>
>>> +#include "devices.h"
>>> +
>>> +static inline struct resource WMT_MMIO_RES(u32 start, u32 size)
>>> +{
>>> + struct resource tmp = {
>>> + .flags = IORESOURCE_MEM,
>>> + .start = start,
>>> + .end = start + size - 1,
>>> + };
>>> +
>>> + return tmp;
>>> +}
>>
>> These functions can be marked __init (though I guess they already are if
>> marked inline?). They should also have lower case names since they are
>> proper functions.
>
> As inline functions are unrolled into the caller at compile time, and
> the caller is __init, I would expect their code to be freed after init
> as well. I could be wrong, though :)
If the compiler decided not to inline them for whatever reason they
would stick around. They should also probably be marked __init to make
it clear that they are not permanent functions.
>> Do these functions generate warnings about returning temporary values
>> off the stack? If so, they could be rewritten as:
>>
>
> Should those be compile-time or run-time? I did not see any.
I thought you might get compile time warnings. Returning things off the
stack in general is error prone. I think passing a pointer to the
resource into the function (as below) maybe a bit better.
>> static __init void wmt_mmio_res(struct resource *res,
>> u32 start, u32 size)
>> {
>> res->flags = IORESOURCE_MEM;
>> res->start = start;
>> res->end = start + size - 1;
>> }
>>
>> You could also make these functions static inline in devices.h to avoid
>> having to define them for each board.
>>
>
> Agreed.
>
>>> +
>>> +static inline struct resource WMT_IRQ_RES(int irq)
>>> +{
>>> + struct resource tmp = {
>>> + .flags = IORESOURCE_IRQ,
>>> + .start = irq,
>>> + .end = irq,
>>> + };
>>> +
>>> + return tmp;
>>> +}
>>> +
>>> +#define WMT_RES_ADD(__device, __resource, __num) \
>>> +if (platform_device_add_resources(__device, __resource, __num)) \
>>> + pr_err("Failed to assign resources to __device##\n");
>>
>> This could be written as a proper function. The resource add is unlikely
>> to fail. Maybe keep the warning but don't worry about printing the
>> device name?
>>
>
> There is memory allocation inside platform_device_add_resources, so
> probably there is scope for failure. I could add unlikely(), though.
I meant more in terms of losing the device name in the error which seems
to be the sole point of the macro. i.e it could be rewritten as:
static void wmt_add_resource(struct platform_device *pdev,
const struct resource *res,
unsigned num)
{
if (platform_device_add_resources(pdev, res, num))
pr_err("Failed to add device resource\n");
}
Because the add resource failing would indicate some serious problem you
may even want to BUG().
~Ryan
--
Bluewater Systems Ltd - ARM Technology Solution Centre
Ryan Mallon 5 Amuri Park, 404 Barbadoes St
ryan@...ewatersys.com PO Box 13 889, Christchurch 8013
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