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SubjectRe: [PATCH 1/4] irqchip, gicv3-its: Read typer register outside the loop
On 30/06/15 15:14, Robert Richter wrote:
> From: Robert Richter <rrichter@cavium.com>
>
> No need to read the typer register in the loop. Values do not change.
>
> Signed-off-by: Robert Richter <rrichter@cavium.com>
> ---
> 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 1b7e155869f6..c5ce21277920 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);
> @@ -825,9 +827,6 @@ 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' was initialized earlier to the default page
> * granule of the the ITS. We can't have an allocation
>

The TYPER value certainly don't change, but there is also only one
device table per ITS instance, so we only read it once. What do we gain
here?

Thanks,

M.
--
Jazz is not dead. It just smells funny...


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