From: Sudhakar Rajashekhara Date: Wed, 26 May 2010 21:41:49 +0000 (-0700) Subject: davinci: mmc: pass number of SG segments as platform data X-Git-Tag: Ubuntu-5.0.0-8.9~22953 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=ca2afb6dbea74ee762ae5856af7045a57a65e9c8;p=mirror_ubuntu-disco-kernel.git davinci: mmc: pass number of SG segments as platform data On some platforms like DM355, the number of EDMA parameter slots available for EDMA_SLOT_ANY usage are few. In such cases, if MMC/SD uses 16 slots for each instance of MMC controller, then the number of slots available for other modules will be very few. By passing the number of EDMA slots to be used in MMC driver from platform data, EDMA slots available for other purposes can be controlled. Most of the platforms will not use this platform data variable. But on DM355, as the number of EDMA resources available is limited, the number of scatter- gather segments used inside the MMC driver can be 8 (passed as platform data) instead of 16. On DM355, when the number of scatter-gather segments was reduced to 8, I saw a performance difference of about 0.25-0.4 Mbytes/sec during write. Read performance variations were negligible. Signed-off-by: Sudhakar Rajashekhara Acked-by: Kevin Hilman Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/arm/mach-davinci/include/mach/mmc.h b/arch/arm/mach-davinci/include/mach/mmc.h index 5a85e24f3673..d4f1e9675069 100644 --- a/arch/arm/mach-davinci/include/mach/mmc.h +++ b/arch/arm/mach-davinci/include/mach/mmc.h @@ -22,6 +22,9 @@ struct davinci_mmc_config { /* Version of the MMC/SD controller */ u8 version; + + /* Number of sg segments */ + u8 nr_sg; }; void davinci_setup_mmc(int module, struct davinci_mmc_config *config); diff --git a/drivers/mmc/host/davinci_mmc.c b/drivers/mmc/host/davinci_mmc.c index 3bd0ba294e9d..547d29c31b40 100644 --- a/drivers/mmc/host/davinci_mmc.c +++ b/drivers/mmc/host/davinci_mmc.c @@ -137,15 +137,15 @@ /* * One scatterlist dma "segment" is at most MAX_CCNT rw_threshold units, - * and we handle up to NR_SG segments. MMC_BLOCK_BOUNCE kicks in only + * and we handle up to MAX_NR_SG segments. MMC_BLOCK_BOUNCE kicks in only * for drivers with max_hw_segs == 1, making the segments bigger (64KB) - * than the page or two that's otherwise typical. NR_SG == 16 gives at - * least the same throughput boost, using EDMA transfer linkage instead - * of spending CPU time copying pages. + * than the page or two that's otherwise typical. nr_sg (passed from + * platform data) == 16 gives at least the same throughput boost, using + * EDMA transfer linkage instead of spending CPU time copying pages. */ #define MAX_CCNT ((1 << 16) - 1) -#define NR_SG 16 +#define MAX_NR_SG 16 static unsigned rw_threshold = 32; module_param(rw_threshold, uint, S_IRUGO); @@ -192,7 +192,7 @@ struct mmc_davinci_host { struct edmacc_param tx_template; struct edmacc_param rx_template; unsigned n_link; - u32 links[NR_SG - 1]; + u32 links[MAX_NR_SG - 1]; /* For PIO we walk scatterlists one segment at a time. */ unsigned int sg_len; @@ -202,6 +202,8 @@ struct mmc_davinci_host { u8 version; /* for ns in one cycle calculation */ unsigned ns_in_one_cycle; + /* Number of sg segments */ + u8 nr_sg; #ifdef CONFIG_CPU_FREQ struct notifier_block freq_transition; #endif @@ -568,6 +570,7 @@ davinci_release_dma_channels(struct mmc_davinci_host *host) static int __init davinci_acquire_dma_channels(struct mmc_davinci_host *host) { + u32 link_size; int r, i; /* Acquire master DMA write channel */ @@ -593,7 +596,8 @@ static int __init davinci_acquire_dma_channels(struct mmc_davinci_host *host) /* Allocate parameter RAM slots, which will later be bound to a * channel as needed to handle a scatterlist. */ - for (i = 0; i < ARRAY_SIZE(host->links); i++) { + link_size = min_t(unsigned, host->nr_sg, ARRAY_SIZE(host->links)); + for (i = 0; i < link_size; i++) { r = edma_alloc_slot(EDMA_CTLR(host->txdma), EDMA_SLOT_ANY); if (r < 0) { dev_dbg(mmc_dev(host->mmc), "dma PaRAM alloc --> %d\n", @@ -1202,6 +1206,12 @@ static int __init davinci_mmcsd_probe(struct platform_device *pdev) init_mmcsd_host(host); + if (pdata->nr_sg) + host->nr_sg = pdata->nr_sg - 1; + + if (host->nr_sg > MAX_NR_SG || !host->nr_sg) + host->nr_sg = MAX_NR_SG; + host->use_dma = use_dma; host->irq = irq;