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de3ee99b09
In may, Steven sent a patch deleting the bounce buffer handling and the CONFIG_MMC_BLOCK_BOUNCE option. I chose the less invasive path of making it a runtime config option, and we merged that successfully for kernel v4.12. The code is however just standing in the way and taking up space for seemingly no gain on any systems in wide use today. Pierre says the code was there to improve speed on TI SDHCI controllers on certain HP laptops and possibly some Ricoh controllers as well. Early SDHCI controllers lacked the scatter-gather feature, which made software bounce buffers a significant speed boost. We are clearly talking about the list of SDHCI PCI-based MMC/SD card readers found in the pci_ids[] list in drivers/mmc/host/sdhci-pci-core.c. The TI SDHCI derivative is not supported by the upstream kernel. This leaves the Ricoh. What we can however notice is that the x86 defconfigs in the kernel did not enable CONFIG_MMC_BLOCK_BOUNCE option, which means that any such laptop would have to have a custom configured kernel to actually take advantage of this bounce buffer speed-up. It simply seems like there was a speed optimization for the Ricoh controllers that noone was using. (I have not checked the distro defconfigs but I am pretty sure the situation is the same there.) Bounce buffers increased performance on the OMAP HSMMC at one point, and was part of the original submission in commita45c6cb816("[ARM] 5369/1: omap mmc: Add new omap hsmmc controller for 2430 and 34xx, v3") This optimization was removed in commit0ccd76d4c2("omap_hsmmc: Implement scatter-gather emulation") which found that scatter-gather emulation provided even better performance. The same was introduced for SDHCI in commit2134a922c6("sdhci: scatter-gather (ADMA) support") I am pretty positively convinced that software scatter-gather emulation will do for any host controller what the bounce buffers were doing. Essentially, the bounce buffer was a reimplementation of software scatter-gather-emulation in the MMC subsystem, and it should be done away with. Cc: Pierre Ossman <pierre@ossman.eu> Cc: Juha Yrjola <juha.yrjola@solidboot.com> Cc: Steven J. Hill <Steven.Hill@cavium.com> Cc: Shawn Lin <shawn.lin@rock-chips.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Suggested-by: Steven J. Hill <Steven.Hill@cavium.com> Suggested-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
87 lines
2.1 KiB
C
87 lines
2.1 KiB
C
#ifndef MMC_QUEUE_H
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#define MMC_QUEUE_H
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#include <linux/types.h>
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#include <linux/blkdev.h>
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#include <linux/blk-mq.h>
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#include <linux/mmc/core.h>
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#include <linux/mmc/host.h>
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static inline struct mmc_queue_req *req_to_mmc_queue_req(struct request *rq)
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{
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return blk_mq_rq_to_pdu(rq);
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}
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struct mmc_queue_req;
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static inline struct request *mmc_queue_req_to_req(struct mmc_queue_req *mqr)
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{
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return blk_mq_rq_from_pdu(mqr);
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}
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struct task_struct;
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struct mmc_blk_data;
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struct mmc_blk_ioc_data;
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struct mmc_blk_request {
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struct mmc_request mrq;
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struct mmc_command sbc;
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struct mmc_command cmd;
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struct mmc_command stop;
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struct mmc_data data;
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int retune_retry_done;
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};
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/**
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* enum mmc_drv_op - enumerates the operations in the mmc_queue_req
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* @MMC_DRV_OP_IOCTL: ioctl operation
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* @MMC_DRV_OP_BOOT_WP: write protect boot partitions
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* @MMC_DRV_OP_GET_CARD_STATUS: get card status
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* @MMC_DRV_OP_GET_EXT_CSD: get the EXT CSD from an eMMC card
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*/
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enum mmc_drv_op {
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MMC_DRV_OP_IOCTL,
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MMC_DRV_OP_BOOT_WP,
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MMC_DRV_OP_GET_CARD_STATUS,
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MMC_DRV_OP_GET_EXT_CSD,
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};
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struct mmc_queue_req {
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struct mmc_blk_request brq;
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struct scatterlist *sg;
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struct mmc_async_req areq;
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enum mmc_drv_op drv_op;
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int drv_op_result;
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void *drv_op_data;
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unsigned int ioc_count;
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};
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struct mmc_queue {
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struct mmc_card *card;
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struct task_struct *thread;
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struct semaphore thread_sem;
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bool suspended;
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bool asleep;
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struct mmc_blk_data *blkdata;
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struct request_queue *queue;
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/*
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* FIXME: this counter is not a very reliable way of keeping
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* track of how many requests that are ongoing. Switch to just
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* letting the block core keep track of requests and per-request
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* associated mmc_queue_req data.
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*/
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int qcnt;
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};
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extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, spinlock_t *,
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const char *);
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extern void mmc_cleanup_queue(struct mmc_queue *);
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extern void mmc_queue_suspend(struct mmc_queue *);
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extern void mmc_queue_resume(struct mmc_queue *);
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extern unsigned int mmc_queue_map_sg(struct mmc_queue *,
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struct mmc_queue_req *);
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extern int mmc_access_rpmb(struct mmc_queue *);
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#endif
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