Re: [PATCH v2 09/28] ARM: mmu: Specify size in bytes in create_sections()

From: Andrey Smirnov <andrew.smirnov@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Barebox List <barebox@lists.infradead.org>
Subject: Re: [PATCH v2 09/28] ARM: mmu: Specify size in bytes in create_sections()
Date: Thu, 17 May 2018 00:01:34 -0700	[thread overview]
Message-ID: <CAHQ1cqG4JE6r_rysqgEARSF2zriVcyr1wWkODswg5cNfp-2NqQ@mail.gmail.com> (raw)
In-Reply-To: <20180517065553.myhqjqp33allblkk@pengutronix.de>

On Wed, May 16, 2018 at 11:55 PM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Wed, May 16, 2018 at 01:00:17PM -0700, Andrey Smirnov wrote:
>> Seeing
>>
>>         create_sections(ttb, 0, PAGE_SIZE, ...);
>>
>> as the code the creates initial flat 4 GiB mapping is a bit less
>> intuitive then
>>
>>         create_sections(ttb, 0, SZ_4G, ...);
>>
>> so, for the sake of clarification, convert create_sections() to accept
>> size in bytes and do bytes -> MiB converstion as a part of the
>> function.
>>
>> NOTE: To keep all of the arguments of create_sections() 32-bit:
>>
>>     - Move all of the real code into a helper function accepting first
>>       and last addresses of the region (e.g passing 0 and U32_MAX
>>       means all 4GiB of address space)
>>
>>     - Convert create_section() into a macro that does necessary size
>>       -> last addres conversion under the hood to preserve original API
>>
>> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
>> ---
>>  arch/arm/cpu/mmu-early.c |  4 ++--
>>  arch/arm/cpu/mmu.c       |  4 ++--
>>  arch/arm/cpu/mmu.h       | 22 ++++++++++++++++------
>>  3 files changed, 20 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm/cpu/mmu-early.c b/arch/arm/cpu/mmu-early.c
>> index 70ece0d2f..136b33c3a 100644
>> --- a/arch/arm/cpu/mmu-early.c
>> +++ b/arch/arm/cpu/mmu-early.c
>> @@ -16,7 +16,7 @@ static void map_cachable(unsigned long start, unsigned long size)
>>       start = ALIGN_DOWN(start, SZ_1M);
>>       size  = ALIGN(size, SZ_1M);
>>
>> -     create_sections(ttb, start, size >> 20, PMD_SECT_AP_WRITE |
>> +     create_sections(ttb, start, size, PMD_SECT_AP_WRITE |
>>                       PMD_SECT_AP_READ | PMD_TYPE_SECT | PMD_SECT_WB);
>>  }
>>
>> @@ -30,7 +30,7 @@ void mmu_early_enable(unsigned long membase, unsigned long memsize,
>>       set_ttbr(ttb);
>>       set_domain(DOMAIN_MANAGER);
>>
>> -     create_sections(ttb, 0, 4096, PMD_SECT_AP_WRITE |
>> +     create_sections(ttb, 0, SZ_4G, PMD_SECT_AP_WRITE |
>>                       PMD_SECT_AP_READ | PMD_TYPE_SECT);
>>
>>       map_cachable(membase, memsize);
>> diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
>> index 0c367e47c..f02c99f65 100644
>> --- a/arch/arm/cpu/mmu.c
>> +++ b/arch/arm/cpu/mmu.c
>> @@ -460,7 +460,7 @@ static int mmu_init(void)
>>       set_domain(DOMAIN_MANAGER);
>>
>>       /* create a flat mapping using 1MiB sections */
>> -     create_sections(ttb, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
>> +     create_sections(ttb, 0, SZ_4G, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
>>                       PMD_TYPE_SECT);
>>       __mmu_cache_flush();
>>
>> @@ -472,7 +472,7 @@ static int mmu_init(void)
>>        * below
>>        */
>>       for_each_memory_bank(bank) {
>> -             create_sections(ttb, bank->start, bank->size >> 20,
>> +             create_sections(ttb, bank->start, bank->size,
>>                               PMD_SECT_DEF_CACHED);
>>               __mmu_cache_flush();
>>       }
>> diff --git a/arch/arm/cpu/mmu.h b/arch/arm/cpu/mmu.h
>> index d71cd7e38..52689359a 100644
>> --- a/arch/arm/cpu/mmu.h
>> +++ b/arch/arm/cpu/mmu.h
>> @@ -27,16 +27,26 @@ static inline void set_domain(unsigned val)
>>  }
>>
>>  static inline void
>> -create_sections(uint32_t *ttb, unsigned long addr,
>> -             int size_m, unsigned int flags)
>> +__create_sections(uint32_t *ttb, unsigned long first,
>> +               unsigned long last, unsigned int flags)
>>  {
>> -     unsigned long ttb_start = addr >> 20;
>> -     unsigned long ttb_end   = ttb_start + size_m;
>> -     unsigned int i;
>> +     unsigned long ttb_start = first >> 20;
>> +     unsigned long ttb_end   = (last >> 20) + 1;
>> +     unsigned int i, addr;
>>
>> -     for (i = ttb_start; i < ttb_end; i++, addr += SZ_1M)
>> +     for (i = ttb_start, addr = first; i < ttb_end; i++, addr += SZ_1M)
>>               ttb[i] = addr | flags;
>>  }
>>
>> +#define create_sections(ttb, addr, size, flags)                              \
>> +     ({                                                              \
>> +             typeof(addr) __addr = addr;                             \
>> +             typeof(size) __size = size;                             \
>> +             /* Check for overflow */                                \
>> +             BUG_ON(__addr > ULONG_MAX - __size + 1);                \
>> +             __create_sections(ttb, __addr, __addr + (size)  - 1,    \
>> +                               flags);                               \
>> +     })
>
> Why do you preserve the original API of create_sections()? I would just
> change it. We have only a few callers and they are easy to change.
>

Mostly because it keeps "addr + size - 1" arithmetic in one place
instead of spreading it to every caller. If you'd rather have that
instead of the macro above, I can change that in v3.

Thanks,
Andrey Smirnov

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