linux-kernel - Re: [PATCH 02/10] irqchip/gic-v3-its: Consolidate LPI_PENDBASE

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Message-ID: <cab043d8-c9bb-6975-8304-ff80dbe62027@arm.com>
Date:   Mon, 24 Sep 2018 11:50:12 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH 02/10] irqchip/gic-v3-its: Consolidate LPI_PENDBASE_SZ
 usage

Hi,

On 24/09/18 11:33, Suzuki K Poulose wrote:
> Hi Marc,
> 
> On 21/09/18 20:59, Marc Zyngier wrote:
>> LPI_PENDING_SZ is always used in conjunction with a max(). Let's
>> factor this in the definition of the macro, and simplify the rest
>> of the code.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>> ---
>>   drivers/irqchip/irq-gic-v3-its.c | 12 ++++--------
>>   1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
>> b/drivers/irqchip/irq-gic-v3-its.c
>> index c2df341ff6fa..ed6aab11e019 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -62,7 +62,7 @@ static u32 lpi_id_bits;
>>    */
>>   #define LPI_NRBITS        lpi_id_bits
>>   #define LPI_PROPBASE_SZ        ALIGN(BIT(LPI_NRBITS), SZ_64K)
>> -#define LPI_PENDBASE_SZ        ALIGN(BIT(LPI_NRBITS) / 8, SZ_64K)
>> +#define LPI_PENDBASE_SZ        max_t(u32, SZ_64K, 
>> ALIGN(BIT(LPI_NRBITS) / 8, SZ_64K))
> 
> minor nit: The ALIGN() already aligns the given value up to the required
> alignment. So, if the LPI_NRBITS is guaranteed to be non-zero,
> we could simply drop the max_t().
> 

Hmmm, Doesn't ALIGN only aligns down? So if "BIT(LPI_NR_BITS) / 8 < 
SZ_64K" (i.e. LPI_NRBITS < 20) The ALIGN(..., SZ_64K) would give 0.

Thanks,

> Rest looks good to me.
> 
> Suzuki
> 
>>   #define LPI_PROP_DEFAULT_PRIO    0xa0
>> @@ -1924,12 +1924,9 @@ static int its_alloc_collections(struct 
>> its_node *its)
>>   static struct page *its_allocate_pending_table(gfp_t gfp_flags)
>>   {
>>       struct page *pend_page;
>> -    /*
>> -     * The pending pages have to be at least 64kB aligned,
>> -     * hence the 'max(LPI_PENDBASE_SZ, SZ_64K)' below.
>> -     */
>> +
>>       pend_page = alloc_pages(gfp_flags | __GFP_ZERO,
>> -                get_order(max_t(u32, LPI_PENDBASE_SZ, SZ_64K)));
>> +                get_order(LPI_PENDBASE_SZ));
>>       if (!pend_page)
>>           return NULL;
>> @@ -1941,8 +1938,7 @@ static struct page 
>> *its_allocate_pending_table(gfp_t gfp_flags)
>>   static void its_free_pending_table(struct page *pt)
>>   {
>> -    free_pages((unsigned long)page_address(pt),
>> -           get_order(max_t(u32, LPI_PENDBASE_SZ, SZ_64K)));
>> +    free_pages((unsigned long)page_address(pt), 
>> get_order(LPI_PENDBASE_SZ));
>>   }
>>   static void its_cpu_init_lpis(void)
>>

-- 
Julien Thierry