From: Philipp Zabel <p.zabel@pengutronix.de>
To: linux-kernel@vger.kernel.org
Cc: "Alexandru Gagniuc" <alex.g@adaptrum.com>,
"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>,
"Baoyou Xie" <baoyou.xie@linaro.org>,
"Eugeniy Paltsev" <Eugeniy.Paltsev@synopsys.com>,
"Steffen Trumtrar" <s.trumtrar@pengutronix.de>,
"Dinh Nguyen" <dinguyen@kernel.org>,
"Andreas Färber" <afaerber@suse.de>,
linux-arm-kernel@lists.infradead.org, kernel@pengutronix.de,
"Philipp Zabel" <p.zabel@pengutronix.de>
Subject: [PATCH v3 5/5] reset: simple: read back to make sure changes are applied
Date: Wed, 16 Aug 2017 11:47:01 +0200 [thread overview]
Message-ID: <20170816094701.30678-6-p.zabel@pengutronix.de> (raw)
In-Reply-To: <20170816094701.30678-1-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 | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/reset/reset-simple.c b/drivers/reset/reset-simple.c
index 13e7d5559acc9..d98a7e7d802d1 100644
--- a/drivers/reset/reset-simple.c
+++ b/drivers/reset/reset-simple.c
@@ -39,17 +39,20 @@ 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));
+ reg = readl(addr);
if (assert ^ data->active_low)
reg |= BIT(offset);
else
reg &= ~BIT(offset);
- writel(reg, data->membase + (bank * reg_width));
+ writel(reg, 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:[~2017-08-16 9:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-16 9:46 [PATCH v3 0/5] Unify simple reset drivers Philipp Zabel
2017-08-16 9:46 ` [PATCH v3 1/5] reset: add reset-simple to unify socfpga, stm32, sunxi, and zx2967 Philipp Zabel
2017-08-16 11:30 ` Andre Przywara
2017-08-16 12:12 ` Andreas Färber
2017-08-16 15:11 ` Philipp Zabel
2017-08-16 15:17 ` Andre Przywara
2017-08-16 16:41 ` Andreas Färber
2017-08-16 16:46 ` Andre Przywara
2017-08-16 20:46 ` Alexandru Gagniuc
2017-08-16 9:46 ` [PATCH v3 2/5] reset: socfpga: use the reset-simple driver Philipp Zabel
2017-08-16 20:46 ` Alexandru Gagniuc
2017-08-21 8:45 ` Philipp Zabel
2017-08-16 9:46 ` [PATCH v3 3/5] reset: stm32: " Philipp Zabel
2017-08-16 12:52 ` Eugeniy Paltsev
2017-08-16 12:55 ` Andreas Färber
2017-08-16 13:03 ` Andre Przywara
2017-08-16 20:50 ` Alexandru Gagniuc
2017-08-16 20:52 ` Andreas Färber
2017-08-16 20:55 ` Alexandru Gagniuc
2017-08-17 9:19 ` Andre Przywara
2017-08-21 8:38 ` Philipp Zabel
2017-08-29 8:39 ` [v3,3/5] " Gabriel FERNANDEZ
2017-08-16 9:47 ` [PATCH v3 4/5] reset: zx2967: " Philipp Zabel
2017-08-16 20:50 ` Alexandru Gagniuc
2017-08-16 9:47 ` Philipp Zabel [this message]
2017-08-16 21:00 ` [PATCH v3 5/5] reset: simple: read back to make sure changes are applied Alexandru Gagniuc
2017-08-21 8:21 ` Philipp Zabel
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