Re: [PATCH] block/ps3: Fix slow VRAM IO

Jim Paris
2009-10-19T20:09:35Z

Geoff Levand wrote:
>
> From: Hideyuki Sasaki <Hideyuki_Sasaki@hq.scei.sony.co.jp>
>
> The current PS3 VRAM driver uses msleep() to wait for completion
> of RSX DMA transfers between system memory and VRAM. Depending
> on the system timing, the processing delay and overhead of this
> msleep() call can significantly impact VRAM driver IO.
>
> To avoid the condition, add a short duration (200 usec max)
> udelay() polling loop before entering the msleep() polling
> loop.
>
> Signed-off-by: Hideyuki Sasaki <xhide@rd.scei.sony.co.jp>
> Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>

Acked-by: Jim Paris <jim@jtan.com>

Thanks for tracking this down.

-jim

> ---
>
> drivers/block/ps3vram.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> --- a/drivers/block/ps3vram.c
> +++ b/drivers/block/ps3vram.c
> @@ -123,7 +123,15 @@ static int ps3vram_notifier_wait(struct
> {
> struct ps3vram_priv *priv = ps3_system_bus_get_drvdata(dev);
> u32 *notify = ps3vram_get_notifier(priv->reports, NOTIFIER);
> - unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
> + unsigned long timeout;
> +
> + for (timeout = 20; timeout; timeout--) {
> + if (!notify[3])
> + return 0;
> + udelay(10);
> + }
> +
> + timeout = jiffies + msecs_to_jiffies(timeout_ms);
>
> do {
> if (!notify[3])