From edd63fcc97cdb53279a7c43fa1691f5913d92793 Mon Sep 17 00:00:00 2001 From: Russell King Date: Tue, 26 Jan 2016 13:39:50 +0000 Subject: [PATCH] mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer Unnecessarily mapping and unmapping the align buffer for SD cards is expensive: performance measurements on iMX6 show that this gives a hit of 10% on hdparm buffered disk reads. MMC/SD card IO comes from the mm/vfs which gives us page based IO, so for this case, the align buffer is not going to be used. However, we still map and unmap this buffer. Eliminate this by switching the align buffer to be a DMA coherent buffer, which needs no DMA maintenance to access the buffer. Signed-off-by: Russell King Signed-off-by: Adrian Hunter Cc: stable@vger.kernel.org # v4.5+ Tested-by: Gregory CLEMENT Signed-off-by: Ulf Hansson --- drivers/mmc/host/sdhci.c | 54 ++++++++++++++-------------------------- 1 file changed, 18 insertions(+), 36 deletions(-) diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 5c90941f31d9..78359baee369 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -465,8 +465,6 @@ static void sdhci_adma_mark_end(void *desc) static int sdhci_adma_table_pre(struct sdhci_host *host, struct mmc_data *data) { - int direction; - void *desc; void *align; dma_addr_t addr; @@ -483,20 +481,9 @@ static int sdhci_adma_table_pre(struct sdhci_host *host, * We currently guess that it is LE. */ - if (data->flags & MMC_DATA_READ) - direction = DMA_FROM_DEVICE; - else - direction = DMA_TO_DEVICE; - - host->align_addr = dma_map_single(mmc_dev(host->mmc), - host->align_buffer, host->align_buffer_sz, direction); - if (dma_mapping_error(mmc_dev(host->mmc), host->align_addr)) - goto fail; - BUG_ON(host->align_addr & SDHCI_ADMA2_MASK); - host->sg_count = sdhci_pre_dma_transfer(host, data); if (host->sg_count < 0) - goto unmap_align; + return -EINVAL; desc = host->adma_table; align = host->align_buffer; @@ -570,22 +557,7 @@ static int sdhci_adma_table_pre(struct sdhci_host *host, /* nop, end, valid */ sdhci_adma_write_desc(host, desc, 0, 0, ADMA2_NOP_END_VALID); } - - /* - * Resync align buffer as we might have changed it. - */ - if (data->flags & MMC_DATA_WRITE) { - dma_sync_single_for_device(mmc_dev(host->mmc), - host->align_addr, host->align_buffer_sz, direction); - } - return 0; - -unmap_align: - dma_unmap_single(mmc_dev(host->mmc), host->align_addr, - host->align_buffer_sz, direction); -fail: - return -EINVAL; } static void sdhci_adma_table_post(struct sdhci_host *host, @@ -605,9 +577,6 @@ static void sdhci_adma_table_post(struct sdhci_host *host, else direction = DMA_TO_DEVICE; - dma_unmap_single(mmc_dev(host->mmc), host->align_addr, - host->align_buffer_sz, direction); - /* Do a quick scan of the SG list for any unaligned mappings */ has_unaligned = false; for_each_sg(data->sg, sg, host->sg_count, i) @@ -2985,14 +2954,21 @@ int sdhci_add_host(struct sdhci_host *host) &host->adma_addr, GFP_KERNEL); host->align_buffer_sz = SDHCI_MAX_SEGS * SDHCI_ADMA2_ALIGN; - host->align_buffer = kmalloc(host->align_buffer_sz, GFP_KERNEL); + host->align_buffer = dma_alloc_coherent(mmc_dev(mmc), + host->align_buffer_sz, + &host->align_addr, + GFP_KERNEL); if (!host->adma_table || !host->align_buffer) { if (host->adma_table) dma_free_coherent(mmc_dev(mmc), host->adma_table_sz, host->adma_table, host->adma_addr); - kfree(host->align_buffer); + if (host->align_buffer) + dma_free_coherent(mmc_dev(mmc), + host->align_buffer_sz, + host->align_buffer, + host->align_addr); pr_warn("%s: Unable to allocate ADMA buffers - falling back to standard DMA\n", mmc_hostname(mmc)); host->flags &= ~SDHCI_USE_ADMA; @@ -3004,10 +2980,14 @@ int sdhci_add_host(struct sdhci_host *host) host->flags &= ~SDHCI_USE_ADMA; dma_free_coherent(mmc_dev(mmc), host->adma_table_sz, host->adma_table, host->adma_addr); - kfree(host->align_buffer); + dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz, + host->align_buffer, host->align_addr); host->adma_table = NULL; host->align_buffer = NULL; } + + /* dma_alloc_coherent returns page aligned and sized buffers */ + BUG_ON(host->align_addr & SDHCI_ADMA2_MASK); } /* @@ -3470,7 +3450,9 @@ void sdhci_remove_host(struct sdhci_host *host, int dead) if (host->adma_table) dma_free_coherent(mmc_dev(mmc), host->adma_table_sz, host->adma_table, host->adma_addr); - kfree(host->align_buffer); + if (host->align_buffer) + dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz, + host->align_buffer, host->align_addr); host->adma_table = NULL; host->align_buffer = NULL; -- 2.20.1