From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sasha Levin <sashal@kernel.org>,
Naga Sureshkumar Relli <naga.sureshkumar.relli@xilinx.com>,
linux-spi@vger.kernel.org, Thommy Jakobsson <thommyj@gmail.com>,
Mark Brown <broonie@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH AUTOSEL 5.5 16/41] spi/zynqmp: remove entry that causes a cs glitch
Date: Sun, 15 Mar 2020 22:32:54 -0400 [thread overview]
Message-ID: <20200316023319.749-16-sashal@kernel.org> (raw)
In-Reply-To: <20200316023319.749-1-sashal@kernel.org>
From: Thommy Jakobsson <thommyj@gmail.com>
[ Upstream commit 5dd8304981ecffa77bb72b1c57c4be5dfe6cfae9 ]
In the public interface for chipselect, there is always an entry
commented as "Dummy generic FIFO entry" pushed down to the fifo right
after the activate/deactivate command. The dummy entry is 0x0,
irregardless if the intention was to activate or deactive the cs. This
causes the cs line to glitch rather than beeing activated in the case
when there was an activate command.
This has been observed on oscilloscope, and have caused problems for at
least one specific flash device type connected to the qspi port. After
the change the glitch is gone and cs goes active when intended.
The reason why this worked before (except for the glitch) was because
when sending the actual data, the CS bits are once again set. Since
most flashes uses mode 0, there is always a half clk period anyway for
cs to clk active setup time. If someone would rely on timing from a
chip_select call to a transfer_one, it would fail though.
It is unknown why the dummy entry was there in the first place, git log
seems to be of no help in this case. The reference manual gives no
indication of the necessity of this. In fact the lower 8 bits are a
setup (or hold in case of deactivate) time expressed in cycles. So this
should not be needed to fulfill any setup/hold timings.
Signed-off-by: Thommy Jakobsson <thommyj@gmail.com>
Reviewed-by: Naga Sureshkumar Relli <naga.sureshkumar.relli@xilinx.com>
Link: https://lore.kernel.org/r/20200224162643.29102-1-thommyj@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-zynqmp-gqspi.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/drivers/spi/spi-zynqmp-gqspi.c b/drivers/spi/spi-zynqmp-gqspi.c
index 60c4de4e44856..7412a3042a8d2 100644
--- a/drivers/spi/spi-zynqmp-gqspi.c
+++ b/drivers/spi/spi-zynqmp-gqspi.c
@@ -401,9 +401,6 @@ static void zynqmp_qspi_chipselect(struct spi_device *qspi, bool is_high)
zynqmp_gqspi_write(xqspi, GQSPI_GEN_FIFO_OFST, genfifoentry);
- /* Dummy generic FIFO entry */
- zynqmp_gqspi_write(xqspi, GQSPI_GEN_FIFO_OFST, 0x0);
-
/* Manually start the generic FIFO command */
zynqmp_gqspi_write(xqspi, GQSPI_CONFIG_OFST,
zynqmp_gqspi_read(xqspi, GQSPI_CONFIG_OFST) |
--
2.20.1
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next prev parent reply other threads:[~2020-03-16 2:36 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200316023319.749-1-sashal@kernel.org>
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 03/41] drm/mediatek: Find the cursor plane instead of hard coding it Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 04/41] drm/mediatek: Ensure the cursor plane is on top of other overlays Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 05/41] ARM: dts: imx6dl-colibri-eval-v3: fix sram compatible properties Sasha Levin
2020-03-16 7:21 ` Johan Hovold
2020-03-22 12:54 ` Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 09/41] ASoC: meson: g12a: add tohdmitx reset Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 15/41] spi: pxa2xx: Add CS control clock quirk Sasha Levin
2020-03-16 2:32 ` Sasha Levin [this message]
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 17/41] ARM: dts: bcm283x: Add missing properties to the PWR LED Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 18/41] drm/exynos: dsi: propagate error value and silence meaningless warning Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 19/41] drm/exynos: dsi: fix workaround for the legacy clock name Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 20/41] drm/exynos: hdmi: don't leak enable HDMI_EN regulator if probe fails Sasha Levin
2020-03-16 2:32 ` [PATCH AUTOSEL 5.5 21/41] drivers/perf: fsl_imx8_ddr: Correct the CLEAR bit definition Sasha Levin
2020-03-16 2:33 ` [PATCH AUTOSEL 5.5 22/41] drivers/perf: arm_pmu_acpi: Fix incorrect checking of gicc pointer Sasha Levin
2020-03-16 2:33 ` [PATCH AUTOSEL 5.5 24/41] ARM: bcm2835_defconfig: Explicitly restore CONFIG_DEBUG_FS Sasha Levin
2020-03-16 2:33 ` [PATCH AUTOSEL 5.5 29/41] ASoC: stm32: sai: manage rebind issue Sasha Levin
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