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mmc: alcor: enable DMA transfer of large buffers

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DMA on this hardware is limited to dealing with a single page at a
time. Previously, the driver was set up accordingly to request single-page
DMA buffers, however that had the effect of generating a large number
of small MMC requests for data I/O.

Improve the driver to accept scatter-gather DMA buffers of larger sizes.
Iterate through those buffers a page at a time.

Testing with dd, this increases write performance from 2mb/sec to
10mb/sec, and increases read performance from 4mb/sec to 14mb/sec.

Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Daniel Drake 2019-04-01 13:42:15 +08:00 committed by Ulf Hansson
parent e374e87538
commit c278150e0d
1 changed files with 35 additions and 53 deletions
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88
drivers/mmc/host/alcor.c
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@ -54,9 +54,9 @@ struct alcor_sdmmc_host {
struct delayed_work timeout_work;
struct sg_mapping_iter sg_miter; /* SG state for PIO */
struct sg_dma_page_iter sg_diter; /* SG state for DMA */
struct scatterlist *sg;
unsigned int blocks; /* remaining PIO blocks */
int sg_count;
u32 irq_status_sd;
unsigned char cur_power_mode;
@ -117,30 +117,19 @@ static void alcor_reset(struct alcor_sdmmc_host *host, u8 val)
dev_err(host->dev, "%s: timeout\n", __func__);
}
/*
* Perform DMA I/O of a single page.
*/
static void alcor_data_set_dma(struct alcor_sdmmc_host *host)
{
struct alcor_pci_priv *priv = host->alcor_pci;
u32 addr;
dma_addr_t addr;
if (!host->sg_count)
if (!__sg_page_iter_dma_next(&host->sg_diter))
return;
if (!host->sg) {
dev_err(host->dev, "have blocks, but no SG\n");
return;
}
if (!sg_dma_len(host->sg)) {
dev_err(host->dev, "DMA SG len == 0\n");
return;
}
addr = (u32)sg_dma_address(host->sg);
alcor_write32(priv, addr, AU6601_REG_SDMA_ADDR);
host->sg = sg_next(host->sg);
host->sg_count--;
addr = sg_page_iter_dma_address(&host->sg_diter);
alcor_write32(priv, (u32) addr, AU6601_REG_SDMA_ADDR);
}
static void alcor_trigger_data_transfer(struct alcor_sdmmc_host *host)
@ -153,12 +142,29 @@ static void alcor_trigger_data_transfer(struct alcor_sdmmc_host *host)
ctrl |= AU6601_DATA_WRITE;
if (data->host_cookie == COOKIE_MAPPED) {
/*
* For DMA transfers, this function is called just once,
* at the start of the operation. The hardware can only
* perform DMA I/O on a single page at a time, so here
* we kick off the transfer with the first page, and expect
* subsequent pages to be transferred upon IRQ events
* indicating that the single-page DMA was completed.
*/
__sg_page_iter_start(&host->sg_diter.base, data->sg,
data->sg_len, 0);
alcor_data_set_dma(host);
ctrl |= AU6601_DATA_DMA_MODE;
host->dma_on = 1;
alcor_write32(priv, data->sg_count * 0x1000,
alcor_write32(priv, data->blksz * data->blocks,
AU6601_REG_BLOCK_SIZE);
} else {
/*
* For PIO transfers, we break down each operation
* into several sector-sized transfers. When one sector has
* complete, the IRQ handler will call this function again
* to kick off the transfer of the next sector.
*/
alcor_write32(priv, data->blksz, AU6601_REG_BLOCK_SIZE);
}
@ -233,9 +239,8 @@ static void alcor_prepare_data(struct alcor_sdmmc_host *host,
host->data->bytes_xfered = 0;
host->blocks = data->blocks;
host->sg = data->sg;
host->sg_count = data->sg_count;
dev_dbg(host->dev, "prepare DATA: sg %i, blocks: %i\n",
host->sg_count, host->blocks);
data->sg_count, host->blocks);
if (data->host_cookie != COOKIE_MAPPED)
alcor_prepare_sg_miter(host);
@ -484,9 +489,6 @@ static int alcor_data_irq_done(struct alcor_sdmmc_host *host, u32 intmask)
alcor_trf_block_pio(host, false);
return 1;
case AU6601_INT_DMA_END:
if (!host->sg_count)
break;
alcor_data_set_dma(host);
break;
default:
@ -523,8 +525,7 @@ static void alcor_data_irq_thread(struct alcor_sdmmc_host *host, u32 intmask)
if (alcor_data_irq_done(host, intmask))
return;
if ((intmask & AU6601_INT_DATA_END) || !host->blocks ||
(host->dma_on && !host->sg_count))
if ((intmask & AU6601_INT_DATA_END) || !host->blocks || host->dma_on)
alcor_finish_data(host);
}
@ -762,8 +763,7 @@ static void alcor_pre_req(struct mmc_host *mmc,
struct alcor_sdmmc_host *host = mmc_priv(mmc);
struct mmc_data *data = mrq->data;
struct mmc_command *cmd = mrq->cmd;
struct scatterlist *sg;
unsigned int i, sg_len;
unsigned int sg_len;
if (!data || !cmd)
return;
@ -785,11 +785,6 @@ static void alcor_pre_req(struct mmc_host *mmc,
if (data->blksz & 3)
return;
for_each_sg(data->sg, sg, data->sg_len, i) {
if (sg->length != AU6601_MAX_DMA_BLOCK_SIZE)
return;
}
/* This data might be unmapped at this time */
sg_len = dma_map_sg(host->dev, data->sg, data->sg_len,
@ -1037,26 +1032,13 @@ static void alcor_init_mmc(struct alcor_sdmmc_host *host)
mmc->caps2 = MMC_CAP2_NO_SDIO;
mmc->ops = &alcor_sdc_ops;
/* The hardware does DMA data transfer of 4096 bytes to/from a single
* buffer address. Scatterlists are not supported, but upon DMA
* completion (signalled via IRQ), the original vendor driver does
* then immediately set up another DMA transfer of the next 4096
* bytes.
*
* This means that we need to handle the I/O in 4096 byte chunks.
* Lacking a way to limit the sglist entries to 4096 bytes, we instead
* impose that only one segment is provided, with maximum size 4096,
* which also happens to be the minimum size. This means that the
* single-entry sglist handled by this driver can be handed directly
* to the hardware, nice and simple.
*
* Unfortunately though, that means we only do 4096 bytes I/O per
* MMC command. A future improvement would be to make the driver
* accept sg lists and entries of any size, and simply iterate
* through them 4096 bytes at a time.
/*
* Enable large requests through iteration of scatterlist pages.
* Limit to 240 sectors per request like the original vendor driver.
*/
mmc->max_segs = AU6601_MAX_DMA_SEGMENTS;
mmc->max_seg_size = AU6601_MAX_DMA_BLOCK_SIZE;
mmc->max_segs = 64;
mmc->max_seg_size = 240 * 512;
mmc->max_blk_count = 240;
mmc->max_req_size = mmc->max_seg_size;
}