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From:   Greentime Hu <green.hu@gmail.com>
Date:   Thu, 9 Nov 2017 15:04:59 +0800
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Subject: Re: [PATCH 12/31] nds32: Device specific operations
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Greentime <greentime@andestech.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Networking <netdev@vger.kernel.org>,
        Vincent Chen <vincentc@andestech.com>, deanbo422@gmail.com
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2017-11-08 17:04 GMT+08:00 Arnd Bergmann <arnd@arndb.de>:
> On Wed, Nov 8, 2017 at 6:55 AM, Greentime Hu <green.hu@gmail.com> wrote:
>
>> +
>> +#define ioremap(cookie,size)           __ioremap(cookie,size,0,1)
>> +#define ioremap_nocache(cookie,size)   __ioremap(cookie,size,0,1)
>> +#define iounmap(cookie)                        __iounmap(cookie)
>
>> +#include <asm-generic/io.h>
>
> asm-generic/io.h now provides an ioremap_nocache() helper along with
> ioremap_uc/ioremap_wc/ioremap_wt, so I think you can remove the
> ioremap_nocache definition here. You might also be able to remove
> __ioremap and __iounmap, and only provide ioremap/iounmap, plus
> the identity macro 'define ioremap ioremap'

Thanks. I will try to use generic ioremap_nocache() helper in the next
version patch.

>> +void __iomem *__ioremap(unsigned long phys_addr, size_t size,
>> +                       unsigned long flags, unsigned long align)
>
> The 'align' argument is unused here, and not used on other architectures
> either.
>

Thanks. I will remove this argument in the next version patch.

>> +{
>> +       struct vm_struct *area;
>> +       unsigned long addr, offset, last_addr;
>> +       pgprot_t prot;
>> +
>> +       /* Don't allow wraparound or zero size */
>> +       last_addr = phys_addr + size - 1;
>> +       if (!size || last_addr < phys_addr)
>> +               return NULL;
>> +
>> +       /*
>> +        * Mappings have to be page-aligned
>> +        */
>> +       offset = phys_addr & ~PAGE_MASK;
>> +       phys_addr &= PAGE_MASK;
>> +       size = PAGE_ALIGN(last_addr + 1) - phys_addr;
>> +
>> +       /*
>> +        * Ok, go for it..
>> +        */
>> +       area = get_vm_area(size, VM_IOREMAP);
>
> Better use get_vm_area_caller here to have the ioremap areas show up
> in a more useful form in /proc/vmallocinfo

Thanks.
I will use get_vm_area_caller() in the next version patch.

> Please also have a look at what you can do for memremap().
>
> Since you have no cacheable version of ioremap_wb/wt, it will
> return an uncached mapping all the time, which is not ideal.

Thanks.
I will study kernel/memremap.c

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