Re: [PATCH V7 1/2] dma-mapping: Rework dma_get_cache_alignment()

From: Robin Murphy
Date: Mon Sep 25 2017 - 08:57:43 EST

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On 25/09/17 10:46, Huacai Chen wrote:
> Make dma_get_cache_alignment() to accept a 'dev' argument. As a result,
> it can return different alignments due to different devices' I/O cache
> coherency.
>
> Currently, MIPS is the only architecture which support coherent & non-
> coherent devices co-exist. This may be changed in the future, so add a
> new get_cache_alignment() function pointer in 'struct dma_map_ops' as a
> generic solution.

FWIW, ARM and arm64 have also supported per-device coherency for quite
some time.

> For compatibility (always return ARCH_DMA_MINALIGN), make all existing
> callers pass a NULL dev argument to dma_get_cache_alignment().
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Huacai Chen <chenhc@xxxxxxxxx> ---
> arch/mips/cavium-octeon/dma-octeon.c | 3 ++-
> arch/mips/include/asm/dma-mapping.h | 2 ++
> arch/mips/loongson64/common/dma-swiotlb.c | 1 +
> arch/mips/mm/dma-default.c | 11 ++++++++++-
> arch/mips/netlogic/common/nlm-dma.c | 3 ++-
> drivers/infiniband/hw/mthca/mthca_main.c | 2 +-
> drivers/media/v4l2-core/videobuf2-dma-contig.c | 2 +-
> drivers/net/ethernet/broadcom/b44.c | 2 +-
> drivers/net/ethernet/ibm/emac/core.h | 2 +-
> drivers/net/ethernet/mellanox/mlx4/main.c | 2 +-
> drivers/spi/spi-qup.c | 4 ++--
> drivers/tty/serial/mpsc.c | 16 ++++++++--------
> drivers/tty/serial/samsung.c | 14 +++++++-------
> include/linux/dma-mapping.h | 17 ++++++++++++-----
> 14 files changed, 51 insertions(+), 30 deletions(-)

I think it might be neater to split this into two patches - one making
the treewide prototype change, then introducing the .get_cache_alignemnt
callback separately - but that's only my personal preference.

Otherwise (and modulo Christoph's comments), I'd say we're nearly there.

Thanks,
Robin.

> diff --git a/arch/mips/cavium-octeon/dma-octeon.c b/arch/mips/cavium-octeon/dma-octeon.c
> index c64bd87..7978237 100644
> --- a/arch/mips/cavium-octeon/dma-octeon.c
> +++ b/arch/mips/cavium-octeon/dma-octeon.c
> @@ -324,7 +324,8 @@ static struct octeon_dma_map_ops _octeon_pci_dma_map_ops = {
> .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
> .sync_sg_for_device = octeon_dma_sync_sg_for_device,
> .mapping_error = swiotlb_dma_mapping_error,
> - .dma_supported = swiotlb_dma_supported
> + .dma_supported = swiotlb_dma_supported,
> + .get_cache_alignment = mips_get_cache_alignment
> },
> };
>
> diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h
> index aba7138..e2c5d9e 100644
> --- a/arch/mips/include/asm/dma-mapping.h
> +++ b/arch/mips/include/asm/dma-mapping.h
> @@ -39,4 +39,6 @@ static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base,
> #endif
> }
>
> +int mips_get_cache_alignment(struct device *dev);
> +
> #endif /* _ASM_DMA_MAPPING_H */
> diff --git a/arch/mips/loongson64/common/dma-swiotlb.c b/arch/mips/loongson64/common/dma-swiotlb.c
> index 34486c1..09cb8a4 100644
> --- a/arch/mips/loongson64/common/dma-swiotlb.c
> +++ b/arch/mips/loongson64/common/dma-swiotlb.c
> @@ -119,6 +119,7 @@ static const struct dma_map_ops loongson_dma_map_ops = {
> .sync_sg_for_device = loongson_dma_sync_sg_for_device,
> .mapping_error = swiotlb_dma_mapping_error,
> .dma_supported = loongson_dma_supported,
> + .get_cache_alignment = mips_get_cache_alignment
> };
>
> void __init plat_swiotlb_setup(void)
> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index c01bd20..c49987e 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
> @@ -394,6 +394,14 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
>
> EXPORT_SYMBOL(dma_cache_sync);
>
> +int mips_get_cache_alignment(struct device *dev)
> +{
> + if (plat_device_is_coherent(dev))
> + return 1;
> + else
> + return ARCH_DMA_MINALIGN;
> +}
> +
> static const struct dma_map_ops mips_default_dma_map_ops = {
> .alloc = mips_dma_alloc_coherent,
> .free = mips_dma_free_coherent,
> @@ -407,7 +415,8 @@ static const struct dma_map_ops mips_default_dma_map_ops = {
> .sync_sg_for_cpu = mips_dma_sync_sg_for_cpu,
> .sync_sg_for_device = mips_dma_sync_sg_for_device,
> .mapping_error = mips_dma_mapping_error,
> - .dma_supported = mips_dma_supported
> + .dma_supported = mips_dma_supported,
> + .get_cache_alignment = mips_get_cache_alignment
> };
>
> const struct dma_map_ops *mips_dma_map_ops = &mips_default_dma_map_ops;
> diff --git a/arch/mips/netlogic/common/nlm-dma.c b/arch/mips/netlogic/common/nlm-dma.c
> index 0ec9d9d..1e107ac 100644
> --- a/arch/mips/netlogic/common/nlm-dma.c
> +++ b/arch/mips/netlogic/common/nlm-dma.c
> @@ -79,7 +79,8 @@ const struct dma_map_ops nlm_swiotlb_dma_ops = {
> .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
> .sync_sg_for_device = swiotlb_sync_sg_for_device,
> .mapping_error = swiotlb_dma_mapping_error,
> - .dma_supported = swiotlb_dma_supported
> + .dma_supported = swiotlb_dma_supported,
> + .get_cache_alignment = mips_get_cache_alignment
> };
>
> void __init plat_swiotlb_setup(void)
> diff --git a/drivers/infiniband/hw/mthca/mthca_main.c b/drivers/infiniband/hw/mthca/mthca_main.c
> index e36a9bc..cac5fac 100644
> --- a/drivers/infiniband/hw/mthca/mthca_main.c
> +++ b/drivers/infiniband/hw/mthca/mthca_main.c
> @@ -416,7 +416,7 @@ static int mthca_init_icm(struct mthca_dev *mdev,
>
> /* CPU writes to non-reserved MTTs, while HCA might DMA to reserved mtts */
> mdev->limits.reserved_mtts = ALIGN(mdev->limits.reserved_mtts * mdev->limits.mtt_seg_size,
> - dma_get_cache_alignment()) / mdev->limits.mtt_seg_size;
> + dma_get_cache_alignment(NULL)) / mdev->limits.mtt_seg_size;
>
> mdev->mr_table.mtt_table = mthca_alloc_icm_table(mdev, init_hca->mtt_base,
> mdev->limits.mtt_seg_size,
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index 9f389f3..7f54739 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -484,7 +484,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
> int ret = 0;
> struct sg_table *sgt;
> unsigned long contig_size;
> - unsigned long dma_align = dma_get_cache_alignment();
> + unsigned long dma_align = dma_get_cache_alignment(NULL);
>
> /* Only cache aligned DMA transfers are reliable */
> if (!IS_ALIGNED(vaddr | size, dma_align)) {
> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
> index a1125d1..291d6af 100644
> --- a/drivers/net/ethernet/broadcom/b44.c
> +++ b/drivers/net/ethernet/broadcom/b44.c
> @@ -2587,7 +2587,7 @@ static inline void b44_pci_exit(void)
>
> static int __init b44_init(void)
> {
> - unsigned int dma_desc_align_size = dma_get_cache_alignment();
> + unsigned int dma_desc_align_size = dma_get_cache_alignment(NULL);
> int err;
>
> /* Setup paramaters for syncing RX/TX DMA descriptors */
> diff --git a/drivers/net/ethernet/ibm/emac/core.h b/drivers/net/ethernet/ibm/emac/core.h
> index 369de2c..236bf37 100644
> --- a/drivers/net/ethernet/ibm/emac/core.h
> +++ b/drivers/net/ethernet/ibm/emac/core.h
> @@ -68,7 +68,7 @@ static inline int emac_rx_size(int mtu)
> return mal_rx_size(ETH_DATA_LEN + EMAC_MTU_OVERHEAD);
> }
>
> -#define EMAC_DMA_ALIGN(x) ALIGN((x), dma_get_cache_alignment())
> +#define EMAC_DMA_ALIGN(x) ALIGN((x), dma_get_cache_alignment(NULL))
>
> #define EMAC_RX_SKB_HEADROOM \
> EMAC_DMA_ALIGN(CONFIG_IBM_EMAC_RX_SKB_HEADROOM)
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> index e61c99e..56b1449 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1660,7 +1660,7 @@ static int mlx4_init_icm(struct mlx4_dev *dev, struct mlx4_dev_cap *dev_cap,
> */
> dev->caps.reserved_mtts =
> ALIGN(dev->caps.reserved_mtts * dev->caps.mtt_entry_sz,
> - dma_get_cache_alignment()) / dev->caps.mtt_entry_sz;
> + dma_get_cache_alignment(NULL)) / dev->caps.mtt_entry_sz;
>
> err = mlx4_init_icm_table(dev, &priv->mr_table.mtt_table,
> init_hca->mtt_base,
> diff --git a/drivers/spi/spi-qup.c b/drivers/spi/spi-qup.c
> index 974a8ce..0c698c3 100644
> --- a/drivers/spi/spi-qup.c
> +++ b/drivers/spi/spi-qup.c
> @@ -862,7 +862,7 @@ static bool spi_qup_can_dma(struct spi_master *master, struct spi_device *spi,
> struct spi_transfer *xfer)
> {
> struct spi_qup *qup = spi_master_get_devdata(master);
> - size_t dma_align = dma_get_cache_alignment();
> + size_t dma_align = dma_get_cache_alignment(NULL);
> int n_words;
>
> if (xfer->rx_buf) {
> @@ -1038,7 +1038,7 @@ static int spi_qup_probe(struct platform_device *pdev)
> master->transfer_one = spi_qup_transfer_one;
> master->dev.of_node = pdev->dev.of_node;
> master->auto_runtime_pm = true;
> - master->dma_alignment = dma_get_cache_alignment();
> + master->dma_alignment = dma_get_cache_alignment(NULL);
> master->max_dma_len = SPI_MAX_XFER;
>
> platform_set_drvdata(pdev, master);
> diff --git a/drivers/tty/serial/mpsc.c b/drivers/tty/serial/mpsc.c
> index 67ffecc..e2f792a 100644
> --- a/drivers/tty/serial/mpsc.c
> +++ b/drivers/tty/serial/mpsc.c
> @@ -81,19 +81,19 @@
> * Number of Tx & Rx descriptors must be powers of 2.
> */
> #define MPSC_RXR_ENTRIES 32
> -#define MPSC_RXRE_SIZE dma_get_cache_alignment()
> +#define MPSC_RXRE_SIZE dma_get_cache_alignment(NULL)
> #define MPSC_RXR_SIZE (MPSC_RXR_ENTRIES * MPSC_RXRE_SIZE)
> -#define MPSC_RXBE_SIZE dma_get_cache_alignment()
> +#define MPSC_RXBE_SIZE dma_get_cache_alignment(NULL)
> #define MPSC_RXB_SIZE (MPSC_RXR_ENTRIES * MPSC_RXBE_SIZE)
>
> #define MPSC_TXR_ENTRIES 32
> -#define MPSC_TXRE_SIZE dma_get_cache_alignment()
> +#define MPSC_TXRE_SIZE dma_get_cache_alignment(NULL)
> #define MPSC_TXR_SIZE (MPSC_TXR_ENTRIES * MPSC_TXRE_SIZE)
> -#define MPSC_TXBE_SIZE dma_get_cache_alignment()
> +#define MPSC_TXBE_SIZE dma_get_cache_alignment(NULL)
> #define MPSC_TXB_SIZE (MPSC_TXR_ENTRIES * MPSC_TXBE_SIZE)
>
> #define MPSC_DMA_ALLOC_SIZE (MPSC_RXR_SIZE + MPSC_RXB_SIZE + MPSC_TXR_SIZE \
> - + MPSC_TXB_SIZE + dma_get_cache_alignment() /* for alignment */)
> + + MPSC_TXB_SIZE + dma_get_cache_alignment(NULL) /* for alignment */)
>
> /* Rx and Tx Ring entry descriptors -- assume entry size is <= cacheline size */
> struct mpsc_rx_desc {
> @@ -738,7 +738,7 @@ static void mpsc_init_hw(struct mpsc_port_info *pi)
>
> mpsc_brg_init(pi, pi->brg_clk_src);
> mpsc_brg_enable(pi);
> - mpsc_sdma_init(pi, dma_get_cache_alignment()); /* burst a cacheline */
> + mpsc_sdma_init(pi, dma_get_cache_alignment(NULL)); /* burst a cacheline */
> mpsc_sdma_stop(pi);
> mpsc_hw_init(pi);
> }
> @@ -798,8 +798,8 @@ static void mpsc_init_rings(struct mpsc_port_info *pi)
> * Descriptors & buffers are multiples of cacheline size and must be
> * cacheline aligned.
> */
> - dp = ALIGN((u32)pi->dma_region, dma_get_cache_alignment());
> - dp_p = ALIGN((u32)pi->dma_region_p, dma_get_cache_alignment());
> + dp = ALIGN((u32)pi->dma_region, dma_get_cache_alignment(NULL));
> + dp_p = ALIGN((u32)pi->dma_region_p, dma_get_cache_alignment(NULL));
>
> /*
> * Partition dma region into rx ring descriptor, rx buffers,
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index 8aca18c..b40a681 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -241,7 +241,7 @@ static void enable_tx_dma(struct s3c24xx_uart_port *ourport)
> /* Enable tx dma mode */
> ucon = rd_regl(port, S3C2410_UCON);
> ucon &= ~(S3C64XX_UCON_TXBURST_MASK | S3C64XX_UCON_TXMODE_MASK);
> - ucon |= (dma_get_cache_alignment() >= 16) ?
> + ucon |= (dma_get_cache_alignment(NULL) >= 16) ?
> S3C64XX_UCON_TXBURST_16 : S3C64XX_UCON_TXBURST_1;
> ucon |= S3C64XX_UCON_TXMODE_DMA;
> wr_regl(port, S3C2410_UCON, ucon);
> @@ -292,7 +292,7 @@ static int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport,
> if (ourport->tx_mode != S3C24XX_TX_DMA)
> enable_tx_dma(ourport);
>
> - dma->tx_size = count & ~(dma_get_cache_alignment() - 1);
> + dma->tx_size = count & ~(dma_get_cache_alignment(NULL) - 1);
> dma->tx_transfer_addr = dma->tx_addr + xmit->tail;
>
> dma_sync_single_for_device(ourport->port.dev, dma->tx_transfer_addr,
> @@ -332,7 +332,7 @@ static void s3c24xx_serial_start_next_tx(struct s3c24xx_uart_port *ourport)
>
> if (!ourport->dma || !ourport->dma->tx_chan ||
> count < ourport->min_dma_size ||
> - xmit->tail & (dma_get_cache_alignment() - 1))
> + xmit->tail & (dma_get_cache_alignment(NULL) - 1))
> s3c24xx_serial_start_tx_pio(ourport);
> else
> s3c24xx_serial_start_tx_dma(ourport, count);
> @@ -718,8 +718,8 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
>
> if (ourport->dma && ourport->dma->tx_chan &&
> count >= ourport->min_dma_size) {
> - int align = dma_get_cache_alignment() -
> - (xmit->tail & (dma_get_cache_alignment() - 1));
> + int align = dma_get_cache_alignment(NULL) -
> + (xmit->tail & (dma_get_cache_alignment(NULL) - 1));
> if (count-align >= ourport->min_dma_size) {
> dma_count = count-align;
> count = align;
> @@ -870,7 +870,7 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
> dma->tx_conf.direction = DMA_MEM_TO_DEV;
> dma->tx_conf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> dma->tx_conf.dst_addr = p->port.mapbase + S3C2410_UTXH;
> - if (dma_get_cache_alignment() >= 16)
> + if (dma_get_cache_alignment(NULL) >= 16)
> dma->tx_conf.dst_maxburst = 16;
> else
> dma->tx_conf.dst_maxburst = 1;
> @@ -1849,7 +1849,7 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
> * so find minimal transfer size suitable for DMA mode
> */
> ourport->min_dma_size = max_t(int, ourport->port.fifosize,
> - dma_get_cache_alignment());
> + dma_get_cache_alignment(NULL));
>
> dbg("%s: initialising port %p...\n", __func__, ourport);
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 29ce981..1326023 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -131,6 +131,7 @@ struct dma_map_ops {
> #ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
> u64 (*get_required_mask)(struct device *dev);
> #endif
> + int (*get_cache_alignment)(struct device *dev);
> int is_phys;
> };
>
> @@ -697,12 +698,18 @@ static inline void *dma_zalloc_coherent(struct device *dev, size_t size,
> }
>
> #ifdef CONFIG_HAS_DMA
> -static inline int dma_get_cache_alignment(void)
> -{
> -#ifdef ARCH_DMA_MINALIGN
> - return ARCH_DMA_MINALIGN;
> +
> +#ifndef ARCH_DMA_MINALIGN
> +#define ARCH_DMA_MINALIGN 1
> #endif
> - return 1;
> +
> +static inline int dma_get_cache_alignment(struct device *dev)
> +{
> + const struct dma_map_ops *ops = get_dma_ops(dev);
> + if (dev && ops && ops->get_cache_alignment)
> + return ops->get_cache_alignment(dev);
> +
> + return ARCH_DMA_MINALIGN; /* compatible behavior */
> }
> #endif
>
>

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