spi: SPI_MASTER_MUST_* with scatter-gather only option and avoiding realloc

Message ID	1431597524-7907-1-git-send-email-kernel@martin.sperl.org (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-spi-owner@kernel.org> From: kernel@martin.sperl.org To: Mark Brown <broonie@kernel.org>, Stephen Warren <swarren@wwwdotorg.org>, Lee Jones <lee@kernel.org>, linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org Cc: Martin Sperl <kernel@martin.sperl.org> Subject: [PATCH] spi: SPI_MASTER_MUST_* with scatter-gather only option and avoiding realloc Date: Thu, 14 May 2015 09:58:44 +0000 Message-Id: <1431597524-7907-1-git-send-email-kernel@martin.sperl.org> In-Reply-To: <20150512165053.GE3066@sirena.org.uk> References: <20150512165053.GE3066@sirena.org.uk> Sender: linux-spi-owner@vger.kernel.org Precedence: bulk

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index ac1760e..ac74456 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -463,7 +463,7 @@ void bcm2835_dma_init(struct spi_master *master, struct device *dev) master->can_dma = bcm2835_spi_can_dma; master->max_dma_len = 65535; /* limitation by BCM2835_SPI_DLEN */ /* need to do TX AND RX DMA, so we need dummy buffers */ - master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX; + master->flags = SPI_MASTER_MUST_RX_SG | SPI_MASTER_MUST_TX_SG; return; diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index d35c1a1..c85cf58 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -471,6 +471,73 @@ static void spi_set_cs(struct spi_device *spi, bool enable) } #ifdef CONFIG_HAS_DMA +static int spi_map_null(struct spi_master *master, struct device *dev, + struct sg_table *sgt, + struct sg_table *sgt_template, + void *buf, + enum dma_data_direction dir) +{ + struct page *vm_page; + unsigned long page_offset; + int sgs = 0; + int i, j, ret; + ssize_t len, l; + + if (is_vmalloc_addr(buf)) { + vm_page = vmalloc_to_page(buf); + if (!vm_page) { + sg_free_table(sgt); + return -ENOMEM; + } + page_offset = offset_in_page(buf); + } else { + vm_page = NULL; + page_offset = 0; + } + + /* count the number of sgs we will need walking the template */ + for (i = 0; i < sgt_template->nents; i++) { + len = sg_dma_len(&sgt_template->sgl[i]); + while (len) { + len -= min_t(size_t, len, PAGE_SIZE); + sgs++; + } + } + + /* now allocate it */ + ret = sg_alloc_table(sgt, sgs, GFP_KERNEL); + if (ret) + return ret; + + /* and iterate over the template to fill our own table */ + for (i = 0, j = 0; i < sgt_template->nents; i++) { + len = sg_dma_len(&sgt_template->sgl[i]); + /* split into multiple transfers if needed */ + while (len) { + l = min_t(size_t, len, PAGE_SIZE); + if (vm_page) + sg_set_page(&sgt->sgl[i], vm_page, + l, page_offset); + else + sg_set_buf(&sgt->sgl[j], buf, l); + len -= l; + j++; + } + } + + ret = dma_map_sg(dev, sgt->sgl, sgt->nents, dir); + if (!ret) + ret = -ENOMEM; + if (ret < 0) { + sg_free_table(sgt); + return ret; + } + + sgt->nents = ret; + + return 0; +} + static int spi_map_buf(struct spi_master *master, struct device *dev, struct sg_table *sgt, void *buf, size_t len, enum dma_data_direction dir) @@ -564,6 +631,37 @@ static int __spi_map_msg(struct spi_master *master, struct spi_message *msg) return ret; } } + + /* + * handle the SPI_MASTER_MUST_*_SG + * note that the situation with tx_buf and rx_buf both NULL + * is checked and handled inside spi_transfer_one_message + */ + if ((!xfer->tx_buf) && (xfer->rx_buf) && + (master->flags & SPI_MASTER_MUST_TX_SG)) { + ret = spi_map_null(master, tx_dev, + &xfer->tx_sg, &xfer->rx_sg, + master->page_tx, + DMA_TO_DEVICE); + if (ret != 0) { + spi_unmap_buf(master, rx_dev, &xfer->rx_sg, + DMA_FROM_DEVICE); + return ret; + } + } + + if ((!xfer->rx_buf) && (xfer->tx_buf) && + (master->flags & SPI_MASTER_MUST_RX_SG)) { + ret = spi_map_null(master, rx_dev, + &xfer->rx_sg, &xfer->tx_sg, + master->page_rx, + DMA_FROM_DEVICE); + if (ret != 0) { + spi_unmap_buf(master, tx_dev, &xfer->tx_sg, + DMA_TO_DEVICE); + return ret; + } + } } master->cur_msg_mapped = true; @@ -587,9 +685,11 @@ static int spi_unmap_msg(struct spi_master *master, struct spi_message *msg) * Restore the original value of tx_buf or rx_buf if they are * NULL. */ - if (xfer->tx_buf == master->dummy_tx) + if ((xfer->tx_buf == master->dummy_tx) || + (xfer->tx_buf == master->page_tx)) xfer->tx_buf = NULL; - if (xfer->rx_buf == master->dummy_rx) + if ((xfer->rx_buf == master->dummy_rx) || + (xfer->rx_buf == master->page_rx)) xfer->rx_buf = NULL; if (!master->can_dma(master, msg->spi, xfer)) @@ -618,8 +718,9 @@ static inline int spi_unmap_msg(struct spi_master *master, static int spi_map_msg(struct spi_master *master, struct spi_message *msg) { struct spi_transfer *xfer; - void *tmp; + void *tmp_tx, *tmp_rx; unsigned int max_tx, max_rx; + int ret; if (master->flags & (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX)) { max_tx = 0; @@ -635,34 +736,53 @@ static int spi_map_msg(struct spi_master *master, struct spi_message *msg) } if (max_tx) { - tmp = krealloc(master->dummy_tx, max_tx, - GFP_KERNEL | GFP_DMA); - if (!tmp) - return -ENOMEM; - master->dummy_tx = tmp; - memset(tmp, 0, max_tx); + if (max_tx > PAGE_SIZE) { + tmp_tx = krealloc(master->dummy_tx, max_tx, + GFP_KERNEL | GFP_DMA); + if (!tmp_tx) + return -ENOMEM; + master->dummy_tx = tmp_tx; + memset(tmp_tx, 0, max_tx); + } else { + tmp_tx = master->page_tx; + } + } else { + tmp_tx = NULL; } - if (max_rx) { - tmp = krealloc(master->dummy_rx, max_rx, - GFP_KERNEL | GFP_DMA); - if (!tmp) - return -ENOMEM; - master->dummy_rx = tmp; + if (max_rx) { + if (max_rx > PAGE_SIZE) { + tmp_rx = krealloc(master->dummy_rx, max_rx, + GFP_KERNEL | GFP_DMA); + if (!tmp_rx) + return -ENOMEM; + master->dummy_rx = tmp_rx; + } else { + tmp_rx = master->page_rx; + } + } else { + tmp_tx = NULL; } if (max_tx || max_rx) { list_for_each_entry(xfer, &msg->transfers, transfer_list) { if (!xfer->tx_buf) - xfer->tx_buf = master->dummy_tx; + xfer->tx_buf = tmp_tx; if (!xfer->rx_buf) - xfer->rx_buf = master->dummy_rx; + xfer->rx_buf = tmp_rx; } } } - return __spi_map_msg(master, msg); + /* if we fail we need to undo the parial mappings + * and fix up the modified rx_buf/tx_buf + */ + ret = __spi_map_msg(master, msg); + if (ret) + spi_unmap_msg(master, msg); + + return ret; } /* @@ -1555,6 +1675,24 @@ int spi_register_master(struct spi_master *master) if (!master->max_dma_len) master->max_dma_len = INT_MAX; + /* we need to set max_dma_len to PAGESIZE for MUST_XX_SG */ + if (master->flags & (SPI_MASTER_MUST_RX_SG | SPI_MASTER_MUST_TX_SG)) + master->max_dma_len = min_t(size_t, + master->max_dma_len, PAGE_SIZE); + /* and allocate some buffers for dma */ + if (master->flags & (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_RX_SG)) { + master->page_rx = devm_kmalloc(&master->dev, + PAGE_SIZE, GFP_DMA); + if (!master->page_rx) + return -ENOMEM; + } + if (master->flags & (SPI_MASTER_MUST_TX | SPI_MASTER_MUST_TX_SG)) { + master->page_tx = devm_kzalloc(&master->dev, + PAGE_SIZE, GFP_DMA); + if (!master->page_tx) + return -ENOMEM; + } + /* register the device, then userspace will see it. * registration fails if the bus ID is in use. */ diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index d673072..1f440ff 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -353,8 +353,10 @@ struct spi_master { #define SPI_MASTER_HALF_DUPLEX BIT(0) /* can't do full duplex */ #define SPI_MASTER_NO_RX BIT(1) /* can't do buffer read */ #define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */ -#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */ -#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */ +#define SPI_MASTER_MUST_RX BIT(3) /* requires rx_buf allocated */ +#define SPI_MASTER_MUST_TX BIT(4) /* requires tx_buf allocated */ +#define SPI_MASTER_MUST_RX_SG BIT(5) /* requires rx sg list */ +#define SPI_MASTER_MUST_TX_SG BIT(6) /* requires tx sg list */ /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; @@ -459,6 +461,10 @@ struct spi_master { /* dummy data for full duplex devices */ void *dummy_rx; void *dummy_tx; + + /* pages for dma-transfers */ + void *page_rx; + void *page_tx; }; static inline void *spi_master_get_devdata(struct spi_master *master)

spi: SPI_MASTER_MUST_* with scatter-gather only option and avoiding realloc

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