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Subject[PATCH 1/3] spi: spi-geni-qcom: Use the FIFO even more
Date
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
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