Re: [PATCH 1/3] clk: rockchip: convert rk3399 pll type to use readl_poll_timeout

Robin Murphy
2020-01-28T15:29:02Z

On 28/01/2020 10:02 am, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
>
> Instead of open coding the polling of the lock status, use the
> handy readl_poll_timeout for this. As the pll locking is normally
> blazingly fast and we don't want to incur additional delays, we're
> not doing any sleeps similar to for example the imx clk-pllv4
> and define a very safe but still short timeout of 1ms.
>
> Suggested-by: Stephen Boyd <sboyd@kernel.org>
> Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
> ---
> drivers/clk/rockchip/clk-pll.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/clk/rockchip/clk-pll.c b/drivers/clk/rockchip/clk-pll.c
> index 198417d56300..43c9fd0086a2 100644
> --- a/drivers/clk/rockchip/clk-pll.c
> +++ b/drivers/clk/rockchip/clk-pll.c
> @@ -585,19 +585,18 @@ static const struct clk_ops rockchip_rk3066_pll_clk_ops = {
> static int rockchip_rk3399_pll_wait_lock(struct rockchip_clk_pll *pll)
> {
> u32 pllcon;
> - int delay = 24000000;
> + int ret;
>
> - /* poll check the lock status in rk3399 xPLLCON2 */
> - while (delay > 0) {
> - pllcon = readl_relaxed(pll->reg_base + RK3399_PLLCON(2));
> - if (pllcon & RK3399_PLLCON2_LOCK_STATUS)
> - return 0;
> + /*
> + * Lock time typical 250, max 500 input clock cycles @24MHz
> + * So define a very safe maximum of 1000us, meaning 24000 cycles.
> + */
> + ret = readl_poll_timeout(pll->reg_base + RK3399_PLLCON(2), pllcon,
> + pllcon & RK3399_PLLCON2_LOCK_STATUS, 0, 1000);

Note that the existing I/O accessor was readl_relaxed(), but using plain
readl_poll_timeout() switches it to regular readl(). It may well not
matter, but since it's not noted as an intentional change it seemed
worth pointing out.

Robin.

> + if (ret)
> + pr_err("%s: timeout waiting for pll to lock\n", __func__);
>
> - delay--;
> - }
> -
> - pr_err("%s: timeout waiting for pll to lock\n", __func__);
> - return -ETIMEDOUT;
> + return ret;
> }
>
> static void rockchip_rk3399_pll_get_params(struct rockchip_clk_pll *pll,