Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
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 1/3] spi: spi-geni-qcom: Use the FIFO even more
Date:   Sat, 12 Sep 2020 14:07:59 -0700
Message-Id: <20200912140730.1.Ie67fa32009b94702d56232c064f1d89065ee8836@changeid>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In commit 902481a78ee4 ("spi: spi-geni-qcom: Actually use our FIFO") I
explained that the maximum size we could program the FIFO was
"mas->tx_fifo_depth - 3" but that I chose "mas->tx_fifo_depth()"
because I was worried about decreased bandwidth.

Since that time:
* All the interconnect patches have landed, making things run at the
  proper speed.
* I've done more measurements.

This lets me confirm that there's really no downside of using the FIFO
more.  Specifically I did "flashrom -p ec -r /tmp/foo.bin" on a
Chromebook and averaged over several runs.

Before: It took 6.66 seconds and 59669 interrupts fired.
After:  It took 6.66 seconds and 47992 interrupts fired.

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

 drivers/spi/spi-geni-qcom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index 0dc3f4c55b0b..7f0bf0dec466 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -308,7 +308,7 @@ static int spi_geni_init(struct spi_geni_master *mas)
 	 * Hardware programming guide suggests to configure
 	 * RX FIFO RFR level to fifo_depth-2.
 	 */
-	geni_se_init(se, mas->tx_fifo_depth / 2, mas->tx_fifo_depth - 2);
+	geni_se_init(se, mas->tx_fifo_depth - 3, mas->tx_fifo_depth - 2);
 	/* Transmit an entire FIFO worth of data per IRQ */
 	mas->tx_wm = 1;
 	ver = geni_se_get_qup_hw_version(se);
-- 
2.28.0.618.gf4bc123cb7-goog