From: Douglas Anderson <dianders@chromium.org>
To: Mark Brown <broonie@kernel.org>
Cc: Akash Asthana <akashast@codeaurora.org>,
swboyd@chromium.org, Douglas Anderson <dianders@chromium.org>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-spi@vger.kernel.org
Subject: [PATCH 3/3] spi: spi-geni-qcom: Slightly optimize setup of bidirectional xfters
Date: Sat, 12 Sep 2020 14:08:01 -0700 [thread overview]
Message-ID: <20200912140730.3.Ided778fb4cd078e36c6b240d1b279cd7a534a313@changeid> (raw)
In-Reply-To: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid>
When setting up a bidirectional transfer we need to program both the
TX and RX lengths. We don't need a memory barrier between those two
writes. Factor out the __iowmb() and use writel_relaxed(). This
saves a fraction of a microsecond of setup overhead on bidirectional
transfers.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
drivers/spi/spi-geni-qcom.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index 92d88bf85a90..6c7e12b68bf0 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -376,15 +376,22 @@ static void setup_fifo_xfer(struct spi_transfer *xfer,
len &= TRANS_LEN_MSK;
mas->cur_xfer = xfer;
+
+ /*
+ * Factor out the __iowmb() so that we can use writel_relaxed() for
+ * both writes below and thus only incur the overhead once even if
+ * we execute both of them.
+ */
+ __iowmb();
+
if (xfer->tx_buf) {
m_cmd |= SPI_TX_ONLY;
mas->tx_rem_bytes = xfer->len;
- writel(len, se->base + SE_SPI_TX_TRANS_LEN);
+ writel_relaxed(len, se->base + SE_SPI_TX_TRANS_LEN);
}
-
if (xfer->rx_buf) {
m_cmd |= SPI_RX_ONLY;
- writel(len, se->base + SE_SPI_RX_TRANS_LEN);
+ writel_relaxed(len, se->base + SE_SPI_RX_TRANS_LEN);
mas->rx_rem_bytes = xfer->len;
}
--
2.28.0.618.gf4bc123cb7-goog
next prev parent reply other threads:[~2020-09-12 21:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-12 21:07 [PATCH 1/3] spi: spi-geni-qcom: Use the FIFO even more Douglas Anderson
2020-09-12 21:08 ` [PATCH 2/3] spi: spi-geni-qcom: Don't program CS_TOGGLE again and again Douglas Anderson
2020-09-12 23:01 ` Bjorn Andersson
2020-09-15 10:40 ` Akash Asthana
2020-09-12 21:08 ` Douglas Anderson [this message]
2020-09-12 22:54 ` [PATCH 3/3] spi: spi-geni-qcom: Slightly optimize setup of bidirectional xfters Bjorn Andersson
2020-09-13 1:09 ` Doug Anderson
2020-09-13 20:35 ` Doug Anderson
2020-09-13 3:45 ` kernel test robot
2020-09-13 7:31 ` kernel test robot
2020-09-12 22:53 ` [PATCH 1/3] spi: spi-geni-qcom: Use the FIFO even more Bjorn Andersson
2020-09-13 1:11 ` Doug Anderson
2020-09-13 3:12 ` Bjorn Andersson
2020-09-14 14:52 ` Mark Brown
2020-09-15 7:30 ` Akash Asthana
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