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* [PATCH] clk: imx: lpcg: write twice when writing lpcg regs
@ 2019-08-27  8:17 Peng Fan
  2019-09-06 17:20 ` Stephen Boyd
  2019-09-09 11:44 ` Dong Aisheng
  0 siblings, 2 replies; 7+ messages in thread
From: Peng Fan @ 2019-08-27  8:17 UTC (permalink / raw)
  To: mturquette, sboyd, shawnguo, s.hauer, festevam, Aisheng Dong
  Cc: kernel, dl-linux-imx, Anson Huang, Jacky Bai, Abel Vesa,
	linux-clk, linux-arm-kernel, linux-kernel, Peng Fan

From: Peng Fan <peng.fan@nxp.com>

There is hardware issue that:
The output clock the LPCG cell will not turn back on as expected,
even though a read of the IPG registers in the LPCG indicates that
the clock should be enabled.

The software workaround is to write twice to enable the LPCG clock
output.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/clk/imx/clk-lpcg-scu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/clk/imx/clk-lpcg-scu.c b/drivers/clk/imx/clk-lpcg-scu.c
index a73a799fb777..7391d0668ec4 100644
--- a/drivers/clk/imx/clk-lpcg-scu.c
+++ b/drivers/clk/imx/clk-lpcg-scu.c
@@ -54,6 +54,11 @@ static int clk_lpcg_scu_enable(struct clk_hw *hw)
 
 	reg |= val << clk->bit_idx;
 	writel(reg, clk->reg);
+	/*
+	 * There is hardware bug. When enabling the LPCG clock
+	 * output, SW can write the enabling value twice
+	 */
+	writel(reg, clk->reg);
 
 	spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags);
 
@@ -71,6 +76,11 @@ static void clk_lpcg_scu_disable(struct clk_hw *hw)
 	reg = readl_relaxed(clk->reg);
 	reg &= ~(CLK_GATE_SCU_LPCG_MASK << clk->bit_idx);
 	writel(reg, clk->reg);
+	/*
+	 * There is hardware bug. When enabling the LPCG clock
+	 * output, SW can write the enabling value twice
+	 */
+	writel(reg, clk->reg);
 
 	spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags);
 }
-- 
2.16.4


^ permalink raw reply	[flat|nested] 7+ messages in thread

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-- links below jump to the message on this page --
2019-08-27  8:17 [PATCH] clk: imx: lpcg: write twice when writing lpcg regs Peng Fan
2019-09-06 17:20 ` Stephen Boyd
2019-09-09 11:51   ` Dong Aisheng
2019-09-10  2:47     ` Anson Huang
2019-09-10 11:50       ` Daniel Baluta
2019-09-13  3:42       ` Shawn Guo
2019-09-09 11:44 ` Dong Aisheng

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