From c3dccb74be28a345a2ebcc224e41b774529b8b8f Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Thu, 18 May 2017 11:29:31 +0200 Subject: [PATCH] mmc: core: Delete bounce buffer Kconfig option This option is activated by all multiplatform configs and what not so we almost always have it turned on, and the memory it saves is negligible, even more so moving forward. The actual bounce buffer only gets allocated only when used, the only thing the ifdefs are saving is a little bit of code. It is highly improper to have this as a Kconfig option that get turned on by Kconfig, make this a pure runtime-thing and let the host decide whether we use bounce buffers. We add a new property "disable_bounce" to the host struct. Notice that mmc_queue_calc_bouncesz() already disables the bounce buffers if host->max_segs != 1, so any arch that has a maximum number of segments higher than 1 will have bounce buffers disabled. The option CONFIG_MMC_BLOCK_BOUNCE is default y so the majority of platforms in the kernel already have it on, and it then gets turned off at runtime since most of these have a host->max_segs > 1. The few exceptions that have host->max_segs == 1 and still turn off the bounce buffering are those that disable it in their defconfig. Those are the following: arch/arm/configs/colibri_pxa300_defconfig arch/arm/configs/zeus_defconfig - Uses MMC_PXA, drivers/mmc/host/pxamci.c - Sets host->max_segs = NR_SG, which is 1 - This needs its bounce buffer deactivated so we set host->disable_bounce to true in the host driver arch/arm/configs/davinci_all_defconfig - Uses MMC_DAVINCI, drivers/mmc/host/davinci_mmc.c - This driver sets host->max_segs to MAX_NR_SG, which is 16 - That means this driver anyways disabled bounce buffers - No special action needed for this platform arch/arm/configs/lpc32xx_defconfig arch/arm/configs/nhk8815_defconfig arch/arm/configs/u300_defconfig - Uses MMC_ARMMMCI, drivers/mmc/host/mmci.[c|h] - This driver by default sets host->max_segs to NR_SG, which is 128, unless a DMA engine is used, and in that case the number of segments are also > 1 - That means this driver already disables bounce buffers - No special action needed for these platforms arch/arm/configs/sama5_defconfig - Uses MMC_SDHCI, MMC_SDHCI_PLTFM, MMC_SDHCI_OF_AT91, MMC_ATMELMCI - Uses drivers/mmc/host/sdhci.c - Normally sets host->max_segs to SDHCI_MAX_SEGS which is 128 and thus disables bounce buffers - Sets host->max_segs to 1 if SDHCI_USE_SDMA is set - SDHCI_USE_SDMA is only set by SDHCI on PCI adapers - That means that for this platform bounce buffers are already disabled at runtime - No special action needed for this platform arch/blackfin/configs/CM-BF533_defconfig arch/blackfin/configs/CM-BF537E_defconfig - Uses MMC_SPI (a simple MMC card connected on SPI pins) - Uses drivers/mmc/host/mmc_spi.c - Sets host->max_segs to MMC_SPI_BLOCKSATONCE which is 128 - That means this platform already disables bounce buffers at runtime - No special action needed for these platforms arch/mips/configs/cavium_octeon_defconfig - Uses MMC_CAVIUM_OCTEON, drivers/mmc/host/cavium.c - Sets host->max_segs to 16 or 1 - Setting host->disable_bounce to be sure for the 1 case arch/mips/configs/qi_lb60_defconfig - Uses MMC_JZ4740, drivers/mmc/host/jz4740_mmc.c - This sets host->max_segs to 128 so bounce buffers are already runtime disabled - No action needed for this platform It would be interesting to come up with a list of the platforms that actually end up using bounce buffers. I have not been able to infer such a list, but it occurs when host->max_segs == 1 and the bounce buffering is not explicitly disabled. Signed-off-by: Linus Walleij Signed-off-by: Ulf Hansson --- drivers/mmc/core/Kconfig | 18 ------------------ drivers/mmc/core/queue.c | 15 +-------------- drivers/mmc/host/cavium.c | 4 +++- drivers/mmc/host/pxamci.c | 6 +++++- include/linux/mmc/host.h | 1 + 5 files changed, 10 insertions(+), 34 deletions(-) diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig index fc1ecda..42e8906 100644 --- a/drivers/mmc/core/Kconfig +++ b/drivers/mmc/core/Kconfig @@ -61,24 +61,6 @@ config MMC_BLOCK_MINORS If unsure, say 8 here. -config MMC_BLOCK_BOUNCE - bool "Use bounce buffer for simple hosts" - depends on MMC_BLOCK - default y - help - SD/MMC is a high latency protocol where it is crucial to - send large requests in order to get high performance. Many - controllers, however, are restricted to continuous memory - (i.e. they can't do scatter-gather), something the kernel - rarely can provide. - - Say Y here to help these restricted hosts by bouncing - requests back and forth from a large buffer. You will get - a big performance gain at the cost of up to 64 KiB of - physical memory. - - If unsure, say Y here. - config SDIO_UART tristate "SDIO UART/GPS class support" depends on TTY diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index 5c37b6b..70ba7f9 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c @@ -219,7 +219,6 @@ static struct mmc_queue_req *mmc_queue_alloc_mqrqs(int qdepth) return mqrq; } -#ifdef CONFIG_MMC_BLOCK_BOUNCE static int mmc_queue_alloc_bounce_bufs(struct mmc_queue_req *mqrq, int qdepth, unsigned int bouncesz) { @@ -258,7 +257,7 @@ static unsigned int mmc_queue_calc_bouncesz(struct mmc_host *host) { unsigned int bouncesz = MMC_QUEUE_BOUNCESZ; - if (host->max_segs != 1) + if (host->max_segs != 1 || (host->caps & MMC_CAP_NO_BOUNCE_BUFF)) return 0; if (bouncesz > host->max_req_size) @@ -273,18 +272,6 @@ static unsigned int mmc_queue_calc_bouncesz(struct mmc_host *host) return bouncesz; } -#else -static inline bool mmc_queue_alloc_bounce(struct mmc_queue_req *mqrq, - int qdepth, unsigned int bouncesz) -{ - return false; -} - -static unsigned int mmc_queue_calc_bouncesz(struct mmc_host *host) -{ - return 0; -} -#endif static int mmc_queue_alloc_sgs(struct mmc_queue_req *mqrq, int qdepth, int max_segs) diff --git a/drivers/mmc/host/cavium.c b/drivers/mmc/host/cavium.c index b8aaf0f..3686d77 100644 --- a/drivers/mmc/host/cavium.c +++ b/drivers/mmc/host/cavium.c @@ -1035,10 +1035,12 @@ int cvm_mmc_of_slot_probe(struct device *dev, struct cvm_mmc_host *host) * We only have a 3.3v supply, we cannot support any * of the UHS modes. We do support the high speed DDR * modes up to 52MHz. + * + * Disable bounce buffers for max_segs = 1 */ mmc->caps |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED | MMC_CAP_ERASE | MMC_CAP_CMD23 | MMC_CAP_POWER_OFF_CARD | - MMC_CAP_3_3V_DDR; + MMC_CAP_3_3V_DDR | MMC_CAP_NO_BOUNCE_BUFF; if (host->use_sg) mmc->max_segs = 16; diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c index c763b40..59ab194 100644 --- a/drivers/mmc/host/pxamci.c +++ b/drivers/mmc/host/pxamci.c @@ -702,7 +702,11 @@ static int pxamci_probe(struct platform_device *pdev) pxamci_init_ocr(host); - mmc->caps = 0; + /* + * This architecture used to disable bounce buffers through its + * defconfig, now it is done at runtime as a host property. + */ + mmc->caps = MMC_CAP_NO_BOUNCE_BUFF; host->cmdat = 0; if (!cpu_is_pxa25x()) { mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_SDIO_IRQ; diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index f186b26..9209f95 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -271,6 +271,7 @@ struct mmc_host { #define MMC_CAP_UHS_SDR50 (1 << 18) /* Host supports UHS SDR50 mode */ #define MMC_CAP_UHS_SDR104 (1 << 19) /* Host supports UHS SDR104 mode */ #define MMC_CAP_UHS_DDR50 (1 << 20) /* Host supports UHS DDR50 mode */ +#define MMC_CAP_NO_BOUNCE_BUFF (1 << 21) /* Disable bounce buffers on host */ #define MMC_CAP_DRIVER_TYPE_A (1 << 23) /* Host supports Driver Type A */ #define MMC_CAP_DRIVER_TYPE_C (1 << 24) /* Host supports Driver Type C */ #define MMC_CAP_DRIVER_TYPE_D (1 << 25) /* Host supports Driver Type D */ -- 2.7.4