From: Philipp Zabel <p.zabel@pengutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Andre Przywara <andre.przywara@arm.com>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Alexandre Torgue <alexandre.torgue@st.com>,
Maxime Ripard <maxime.ripard@free-electrons.com>,
Chen-Yu Tsai <wens@csie.org>,
Philipp Zabel <p.zabel@pengutronix.de>
Subject: [PATCH 2/2] reset: simple: read back to make sure changes are applied
Date: Wed, 8 Mar 2017 10:54:23 +0100 [thread overview]
Message-ID: <20170308095423.3948-2-p.zabel@pengutronix.de> (raw)
In-Reply-To: <20170308095423.3948-1-p.zabel@pengutronix.de>
Read back the register after setting or clearing a reset bit to make
sure that the changes are applied to the reset controller hardware.
Theoretically, this avoids the write to stay stuck in a store buffer
during the delay of an assert-delay-deassert sequence, and makes sure
that the reset really is asserted for the specified duration.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
drivers/reset/reset-simple.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/reset/reset-simple.c b/drivers/reset/reset-simple.c
index 2160e84fe216b..e32289bdaf0c6 100644
--- a/drivers/reset/reset-simple.c
+++ b/drivers/reset/reset-simple.c
@@ -33,13 +33,16 @@ static int reset_simple_clear(struct reset_controller_dev *rcdev,
int reg_width = sizeof(u32);
int bank = id / (reg_width * BITS_PER_BYTE);
int offset = id % (reg_width * BITS_PER_BYTE);
+ void __iomem *addr = data->membase + (bank * reg_width);
unsigned long flags;
u32 reg;
spin_lock_irqsave(&data->lock, flags);
- reg = readl(data->membase + (bank * reg_width));
- writel(reg & ~BIT(offset), data->membase + (bank * reg_width));
+ reg = readl(addr);
+ writel(reg & ~BIT(offset), addr);
+ /* Read back to make sure the write doesn't linger in a store buffer */
+ readl(addr);
spin_unlock_irqrestore(&data->lock, flags);
@@ -53,13 +56,16 @@ static int reset_simple_set(struct reset_controller_dev *rcdev,
int reg_width = sizeof(u32);
int bank = id / (reg_width * BITS_PER_BYTE);
int offset = id % (reg_width * BITS_PER_BYTE);
+ void __iomem *addr = data->membase + (bank * reg_width);
unsigned long flags;
u32 reg;
spin_lock_irqsave(&data->lock, flags);
- reg = readl(data->membase + (bank * reg_width));
- writel(reg | BIT(offset), data->membase + (bank * reg_width));
+ reg = readl(addr);
+ writel(reg | BIT(offset), addr);
+ /* Read back to make sure the write doesn't linger in a store buffer */
+ readl(addr);
spin_unlock_irqrestore(&data->lock, flags);
--
2.11.0
next prev parent reply other threads:[~2017-03-08 9:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-08 9:54 [PATCH 1/2] reset: add reset-simple to unify socfpga, stm32, and sunxi Philipp Zabel
2017-03-08 9:54 ` Philipp Zabel [this message]
2017-03-08 14:04 ` [PATCH 2/2] reset: simple: read back to make sure changes are applied Andre Przywara
2017-03-08 10:19 ` [PATCH 1/2] reset: add reset-simple to unify socfpga, stm32, and sunxi Andre Przywara
2017-03-08 11:05 ` Alexandre Torgue
2017-03-08 12:20 ` Philipp Zabel
2017-03-08 14:03 ` Andre Przywara
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