linux-kernel - Re: [PATCH 3/4] arm64: gicv3: its: Read typer register outside the loop

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Message-ID: <20150520131524.09d325fe@why.wild-wind.fr.eu.org>
Date:	Wed, 20 May 2015 13:15:24 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Robert Richter <rric@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Tirumalesh Chalamarla <tchalamarla@...ium.com>,
	Radha Mohan Chintakuntla <rchintakuntla@...ium.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Robert Richter <rrichter@...ium.com>
Subject: Re: [PATCH 3/4] arm64: gicv3: its: Read typer register outside the
 loop

On Sun, 3 May 2015 21:49:31 +0100
Robert Richter <rric@...nel.org> wrote:

> From: Robert Richter <rrichter@...ium.com>
> 
> No need to read the typer register in the loop. Values do not change.
> 
> Signed-off-by: Robert Richter <rrichter@...ium.com>

Fair enough.

Acked-by: Marc Zyngier <marc.zyngier@....com>

	M.

> ---
>  drivers/irqchip/irq-gic-v3-its.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index a2619a1d5bb3..916c4724c771 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -803,6 +803,8 @@ static int its_alloc_tables(struct its_node *its)
>  	int psz = SZ_64K;
>  	u64 shr = GITS_BASER_InnerShareable;
>  	u64 cache = GITS_BASER_WaWb;
> +	u64 typer = readq_relaxed(its->base + GITS_TYPER);
> +	u32 ids = GITS_TYPER_DEVBITS(typer);
>  
>  	for (i = 0; i < GITS_BASER_NR_REGS; i++) {
>  		u64 val = readq_relaxed(its->base + GITS_BASER + i * 8);
> @@ -826,9 +828,6 @@ static int its_alloc_tables(struct its_node *its)
>  		 * For other tables, only allocate a single page.
>  		 */
>  		if (type == GITS_BASER_TYPE_DEVICE) {
> -			u64 typer = readq_relaxed(its->base + GITS_TYPER);
> -			u32 ids = GITS_TYPER_DEVBITS(typer);
> -
>  			order = get_order((1UL << ids) * entry_size);
>  			if (order >= MAX_ORDER) {
>  				order = MAX_ORDER - 1;



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