[PATCH 1/4] phy: rockchip-emmc: give DLL some extra time to be ready
dianders at chromium.org
Fri May 13 15:01:56 PDT 2016
On Thu, May 12, 2016 at 3:43 PM, Brian Norris <briannorris at chromium.org> wrote:
> From: Shawn Lin <shawn.lin at rock-chips.com>
> According to the databook, 10.2us is the max time for dll to be ready to
> work. However in testing, some chips need 20us for dll to be ready. This
> patch adds some extra margin for dllrdy to be ready, fixing our
> -ETIMEDOUT issues.
> Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
> Signed-off-by: Brian Norris <briannorris at chromium.org>
> drivers/phy/phy-rockchip-emmc.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
> diff --git a/drivers/phy/phy-rockchip-emmc.c b/drivers/phy/phy-rockchip-emmc.c
> index 6ebcf3e41c46..48cbe691a889 100644
> --- a/drivers/phy/phy-rockchip-emmc.c
> +++ b/drivers/phy/phy-rockchip-emmc.c
> @@ -119,10 +119,11 @@ static int rockchip_emmc_phy_power(struct rockchip_emmc_phy *rk_phy,
> - * After enable analog DLL circuits, we need extra 10.2us
> - * for dll to be ready for work.
> + * After enable analog DLL circuits, we need an extra 10.2us
> + * for dll to be ready for work. But according to testing, we
> + * find some chips need more than 25us.
> - udelay(11);
> + udelay(30);
> rk_phy->reg_offset + GRF_EMMCPHY_STATUS,
Seems sane. This is a "random delay" but you've documented it well,
and an extra 19 microseconds won't be the end of the world.
If we truly trusted the "DLLRDY" bit we could actually do a loop here,
but it's probably not worth it...
Reviewed-by: Douglas Anderson <dianders at chromium.org>
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