From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vignesh R Subject: [PATCH v2 2/2] spi: spi-ti-qspi: Use bounce buffer if read buffer is not DMA'ble Date: Tue, 11 Apr 2017 17:22:25 +0530 Message-ID: <20170411115225.31709-3-vigneshr@ti.com> References: <20170411115225.31709-1-vigneshr@ti.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , , , Vignesh R To: Mark Brown Return-path: In-Reply-To: <20170411115225.31709-1-vigneshr@ti.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org Flash filesystems like JFFS2, UBIFS and MTD block layer can provide vmalloc'd or kmap'd buffers that cannot be mapped using dma_map_sg() and can potentially be in memory region above 32bit addressable region(ie buffers belonging to memory region backed by LPAE) of DMA, implement spi_flash_can_dma() interface to inform SPI core not to map such buffers. When buffers are not mapped for DMA, then use a pre allocated bounce buffer(64K = typical flash erase sector size) to read from flash and then do a copy to actual destination buffer. This is approach is much faster than using memcpy using CPU and also reduces CPU load. With this patch, UBIFS read speed is ~18MB/s and CPU utilization <20% on DRA74 Rev H EVM. Performance degradation is negligible when compared with non bounce buffer case while using UBIFS. Signed-off-by: Vignesh R --- v2: Fix compiler warnings and sparse warnings reported by Kbuild bot. drivers/spi/spi-ti-qspi.c | 66 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 59 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c index 7b39bc204a30..c24d9b45a27c 100644 --- a/drivers/spi/spi-ti-qspi.c +++ b/drivers/spi/spi-ti-qspi.c @@ -33,6 +33,7 @@ #include #include #include +#include #include @@ -57,6 +58,8 @@ struct ti_qspi { struct ti_qspi_regs ctx_reg; dma_addr_t mmap_phys_base; + dma_addr_t rx_bb_dma_addr; + void *rx_bb_addr; struct dma_chan *rx_chan; u32 spi_max_frequency; @@ -126,6 +129,8 @@ struct ti_qspi { #define QSPI_SETUP_ADDR_SHIFT 8 #define QSPI_SETUP_DUMMY_SHIFT 10 +#define QSPI_DMA_BUFFER_SIZE SZ_64K + static inline unsigned long ti_qspi_read(struct ti_qspi *qspi, unsigned long reg) { @@ -429,6 +434,35 @@ static int ti_qspi_dma_xfer(struct ti_qspi *qspi, dma_addr_t dma_dst, return 0; } +static int ti_qspi_dma_bounce_buffer(struct ti_qspi *qspi, + struct spi_flash_read_message *msg) +{ + size_t readsize = msg->len; + void *to = msg->buf; + dma_addr_t dma_src = qspi->mmap_phys_base + msg->from; + int ret = 0; + + /* + * Use bounce buffer as FS like jffs2, ubifs may pass + * buffers that does not belong to kernel lowmem region. + */ + while (readsize != 0) { + size_t xfer_len = min_t(size_t, QSPI_DMA_BUFFER_SIZE, + readsize); + + ret = ti_qspi_dma_xfer(qspi, qspi->rx_bb_dma_addr, + dma_src, xfer_len); + if (ret != 0) + return ret; + memcpy(to, qspi->rx_bb_addr, xfer_len); + readsize -= xfer_len; + dma_src += xfer_len; + to += xfer_len; + } + + return ret; +} + static int ti_qspi_dma_xfer_sg(struct ti_qspi *qspi, struct sg_table rx_sg, loff_t from) { @@ -496,6 +530,12 @@ static void ti_qspi_setup_mmap_read(struct spi_device *spi, QSPI_SPI_SETUP_REG(spi->chip_select)); } +static bool ti_qspi_spi_flash_can_dma(struct spi_device *spi, + struct spi_flash_read_message *msg) +{ + return virt_addr_valid(msg->buf); +} + static int ti_qspi_spi_flash_read(struct spi_device *spi, struct spi_flash_read_message *msg) { @@ -509,15 +549,12 @@ static int ti_qspi_spi_flash_read(struct spi_device *spi, ti_qspi_setup_mmap_read(spi, msg); if (qspi->rx_chan) { - if (msg->cur_msg_mapped) { + if (msg->cur_msg_mapped) ret = ti_qspi_dma_xfer_sg(qspi, msg->rx_sg, msg->from); - if (ret) - goto err_unlock; - } else { - dev_err(qspi->dev, "Invalid address for DMA\n"); - ret = -EIO; + else + ret = ti_qspi_dma_bounce_buffer(qspi, msg); + if (ret) goto err_unlock; - } } else { memcpy_fromio(msg->buf, qspi->mmap_base + msg->from, msg->len); } @@ -723,6 +760,17 @@ static int ti_qspi_probe(struct platform_device *pdev) ret = 0; goto no_dma; } + qspi->rx_bb_addr = dma_alloc_coherent(qspi->dev, + QSPI_DMA_BUFFER_SIZE, + &qspi->rx_bb_dma_addr, + GFP_KERNEL | GFP_DMA); + if (!qspi->rx_bb_addr) { + dev_err(qspi->dev, + "dma_alloc_coherent failed, using PIO mode\n"); + dma_release_channel(qspi->rx_chan); + goto no_dma; + } + master->spi_flash_can_dma = ti_qspi_spi_flash_can_dma; master->dma_rx = qspi->rx_chan; init_completion(&qspi->transfer_complete); if (res_mmap) @@ -763,6 +811,10 @@ static int ti_qspi_remove(struct platform_device *pdev) pm_runtime_put_sync(&pdev->dev); pm_runtime_disable(&pdev->dev); + if (qspi->rx_bb_addr) + dma_free_coherent(qspi->dev, QSPI_DMA_BUFFER_SIZE, + qspi->rx_bb_addr, + qspi->rx_bb_dma_addr); if (qspi->rx_chan) dma_release_channel(qspi->rx_chan); -- 2.11.0