Re: [PATCH v8 13/21] clk: tegra210: Use fence_udelay during PLLU init

From: Sowjanya Komatineni
Date: Sun Aug 11 2019 - 15:16:55 EST



On 8/11/19 11:02 AM, Dmitry Osipenko wrote:
09.08.2019 2:46, Sowjanya Komatineni ÐÐÑÐÑ:
This patch uses fence_udelay rather than udelay during PLLU
initialization to ensure writes to clock registers happens before
waiting for specified delay.

Acked-by: Thierry Reding <treding@xxxxxxxxxx>
Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
---
drivers/clk/tegra/clk-tegra210.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
index 4721ee030d1c..998bf60b219a 100644
--- a/drivers/clk/tegra/clk-tegra210.c
+++ b/drivers/clk/tegra/clk-tegra210.c
@@ -2841,7 +2841,7 @@ static int tegra210_enable_pllu(void)
reg = readl_relaxed(clk_base + pllu.params->ext_misc_reg[0]);
reg &= ~BIT(pllu.params->iddq_bit_idx);
writel_relaxed(reg, clk_base + pllu.params->ext_misc_reg[0]);
- udelay(5);
+ fence_udelay(5, clk_base);
reg = readl_relaxed(clk_base + PLLU_BASE);
reg &= ~GENMASK(20, 0);
@@ -2849,7 +2849,7 @@ static int tegra210_enable_pllu(void)
reg |= fentry->n << 8;
reg |= fentry->p << 16;
writel(reg, clk_base + PLLU_BASE);
- udelay(1);
+ fence_udelay(1, clk_base);
reg |= PLL_ENABLE;
writel(reg, clk_base + PLLU_BASE);
@@ -2895,12 +2895,12 @@ static int tegra210_init_pllu(void)
reg = readl_relaxed(clk_base + XUSB_PLL_CFG0);
reg &= ~XUSB_PLL_CFG0_PLLU_LOCK_DLY_MASK;
writel_relaxed(reg, clk_base + XUSB_PLL_CFG0);
- udelay(1);
+ fence_udelay(1, clk_base);
reg = readl_relaxed(clk_base + PLLU_HW_PWRDN_CFG0);
reg |= PLLU_HW_PWRDN_CFG0_SEQ_ENABLE;
writel_relaxed(reg, clk_base + PLLU_HW_PWRDN_CFG0);
- udelay(1);
+ fence_udelay(1, clk_base);
reg = readl_relaxed(clk_base + PLLU_BASE);
reg &= ~PLLU_BASE_CLKENABLE_USB;

The clk_base corresponds to the RESET controller's part of Clock-and-Reset hardware, is it
okay to read-back the RST register and not the clock for the fencing?
Yes as both reset and clocks are all in same CAR