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* [PATCH] spi: spi-geni-qcom: Don't set the cs if it was already right
@ 2020-06-26 22:19 Douglas Anderson
  2020-06-29 11:53 ` Mark Brown
  2020-06-29 19:38 ` Mark Brown
  0 siblings, 2 replies; 4+ messages in thread
From: Douglas Anderson @ 2020-06-26 22:19 UTC (permalink / raw)
  To: Mark Brown
  Cc: linux-arm-msm, swboyd, Dilip Kota, Bjorn Andersson, Andy Gross,
	Douglas Anderson, linux-kernel, linux-spi

Setting the chip select on the Qualcomm geni SPI controller isn't
exactly cheap.  Let's cache the current setting and avoid setting the
chip select if it's already right.

Using "flashrom" to read or write the EC firmware on a Chromebook
shows roughly a 25% reduction in interrupts and a 15% speedup.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/spi/spi-geni-qcom.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index 5b1dca1fff79..e99a9d57449f 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -79,6 +79,7 @@ struct spi_geni_master {
 	unsigned int oversampling;
 	spinlock_t lock;
 	int irq;
+	bool cs_flag;
 };
 
 static int get_spi_clk_cfg(unsigned int speed_hz,
@@ -146,10 +147,15 @@ static void spi_geni_set_cs(struct spi_device *slv, bool set_flag)
 	struct geni_se *se = &mas->se;
 	unsigned long time_left;
 
-	pm_runtime_get_sync(mas->dev);
 	if (!(slv->mode & SPI_CS_HIGH))
 		set_flag = !set_flag;
 
+	if (set_flag == mas->cs_flag)
+		return;
+
+	mas->cs_flag = set_flag;
+
+	pm_runtime_get_sync(mas->dev);
 	spin_lock_irq(&mas->lock);
 	reinit_completion(&mas->cs_done);
 	if (set_flag)
-- 
2.27.0.212.ge8ba1cc988-goog


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2020-06-26 22:19 [PATCH] spi: spi-geni-qcom: Don't set the cs if it was already right Douglas Anderson
2020-06-29 11:53 ` Mark Brown
2020-06-29 23:45   ` Doug Anderson
2020-06-29 19:38 ` Mark Brown

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