From 49c2fc20d7d7d703763e9b0a6f68313a349a84b9 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Sat, 27 Aug 2016 15:10:30 -0600 Subject: [PATCH] rockchip: spi: Improve SPI read efficiency The SPI driver is quite slow at reading data. For example, with a 24MHz clock on gru it achieves a read speed of only 13.9Mbps. We can correct this by reading the status registers once, then reading as many bytes as are available before checking the status registers again. It seems likely that a status register read requires synchronizing with the SPI FIFO clock domain, which takes a while. BUG=chrome-os-partner:56556 BRANCH=none TEST=run on gru and see the speed increase from 13.920 Mbps to 24.712 Mbps Change-Id: I42745f01f0fe069f6ae26d866004d36bb257e6b2 Signed-off-by: Simon Glass Reviewed-on: https://chromium-review.googlesource.com/376945 Reviewed-by: Julius Werner --- src/soc/rockchip/common/include/soc/spi.h | 7 +++++++ src/soc/rockchip/common/spi.c | 15 +++++++++++---- 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/src/soc/rockchip/common/include/soc/spi.h b/src/soc/rockchip/common/include/soc/spi.h index 7e9e568e6d..dcaa4711d2 100644 --- a/src/soc/rockchip/common/include/soc/spi.h +++ b/src/soc/rockchip/common/include/soc/spi.h @@ -165,6 +165,13 @@ check_member(rockchip_spi, rxdr, 0x800); #define SPI_OMOD_SLAVE 0x01 /* --------Bit fields in CTRLR0--------end */ + +/* TXFLR bits */ +#define TXFLR_LEVEL_MASK 0x3f + +/* RXFLR bits */ +#define RXFLR_LEVEL_MASK 0x3f + /* Bit fields in SR, 7 bits */ #define SR_MASK 0x7f #define SR_BUSY (1 << 0) diff --git a/src/soc/rockchip/common/spi.c b/src/soc/rockchip/common/spi.c index 6784f5b975..f35f91589f 100644 --- a/src/soc/rockchip/common/spi.c +++ b/src/soc/rockchip/common/spi.c @@ -235,11 +235,18 @@ static int do_xfer(struct rockchip_spi *regs, const void *dout, xferred = 1; } + /* + * Try to read as many bytes as are available in one go. + * Reading the status registers probably requires + * sychronizing with the SPI clock which is pretty slow. + */ if (*bytes_in && !(sr & SR_RF_EMPT)) { - *in_buf = read32(®s->rxdr) & 0xff; - in_buf++; - *bytes_in -= 1; - xferred = 1; + int todo = read32(®s->rxflr) & RXFLR_LEVEL_MASK; + + *bytes_in -= todo; + xferred = todo; + while (todo-- > 0) + *in_buf++ = read32(®s->rxdr) & 0xff; } min_xfer -= xferred;