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mmc: tmio_mmc: implement a bounce buffer for unaligned DMA
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For example, with SDIO WLAN cards, some transfers happen with buffers at
odd addresses, whereas the SH-Mobile DMA engine requires even addresses
for SDHI. This patch extends the tmio driver with a bounce buffer, that
is used for single entry scatter-gather lists both for sending and
receiving. If we ever encounter unaligned transfers with multi-element
sg lists, this patch will have to be extended. For now it just falls
back to PIO in this and other unsupported cases.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
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Guennadi Liakhovetski authored and Chris Ball committed Jan 9, 2011
1 parent e0bc6ff commit 9317305
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Showing 2 changed files with 84 additions and 6 deletions.
89 changes: 83 additions & 6 deletions drivers/mmc/host/tmio_mmc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,8 @@
sd_ctrl_write32((host), CTL_STATUS, ~(i)); \
} while (0)

/* This is arbitrary, just noone needed any higher alignment yet */
#define MAX_ALIGN 4

struct tmio_mmc_host {
void __iomem *ctl;
Expand All @@ -127,6 +129,7 @@ struct tmio_mmc_host {

/* pio related stuff */
struct scatterlist *sg_ptr;
struct scatterlist *sg_orig;
unsigned int sg_len;
unsigned int sg_off;

Expand All @@ -139,9 +142,13 @@ struct tmio_mmc_host {
struct tasklet_struct dma_issue;
#ifdef CONFIG_TMIO_MMC_DMA
unsigned int dma_sglen;
u8 bounce_buf[PAGE_CACHE_SIZE] __attribute__((aligned(MAX_ALIGN)));
struct scatterlist bounce_sg;
#endif
};

static void tmio_check_bounce_buffer(struct tmio_mmc_host *host);

static u16 sd_ctrl_read16(struct tmio_mmc_host *host, int addr)
{
return readw(host->ctl + (addr << host->bus_shift));
Expand Down Expand Up @@ -180,6 +187,7 @@ static void tmio_mmc_init_sg(struct tmio_mmc_host *host, struct mmc_data *data)
{
host->sg_len = data->sg_len;
host->sg_ptr = data->sg;
host->sg_orig = data->sg;
host->sg_off = 0;
}

Expand Down Expand Up @@ -438,6 +446,8 @@ static void tmio_mmc_do_data_irq(struct tmio_mmc_host *host)
if (data->flags & MMC_DATA_READ) {
if (!host->chan_rx)
disable_mmc_irqs(host, TMIO_MASK_READOP);
else
tmio_check_bounce_buffer(host);
dev_dbg(&host->pdev->dev, "Complete Rx request %p\n",
host->mrq);
} else {
Expand Down Expand Up @@ -529,8 +539,7 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host,
if (!host->chan_rx)
enable_mmc_irqs(host, TMIO_MASK_READOP);
} else {
struct dma_chan *chan = host->chan_tx;
if (!chan)
if (!host->chan_tx)
enable_mmc_irqs(host, TMIO_MASK_WRITEOP);
else
tasklet_schedule(&host->dma_issue);
Expand Down Expand Up @@ -612,6 +621,16 @@ static irqreturn_t tmio_mmc_irq(int irq, void *devid)
}

#ifdef CONFIG_TMIO_MMC_DMA
static void tmio_check_bounce_buffer(struct tmio_mmc_host *host)
{
if (host->sg_ptr == &host->bounce_sg) {
unsigned long flags;
void *sg_vaddr = tmio_mmc_kmap_atomic(host->sg_orig, &flags);
memcpy(sg_vaddr, host->bounce_buf, host->bounce_sg.length);
tmio_mmc_kunmap_atomic(sg_vaddr, &flags);
}
}

static void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
{
#if defined(CONFIG_SUPERH) || defined(CONFIG_ARCH_SHMOBILE)
Expand All @@ -634,11 +653,35 @@ static void tmio_dma_complete(void *arg)

static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
{
struct scatterlist *sg = host->sg_ptr;
struct scatterlist *sg = host->sg_ptr, *sg_tmp;
struct dma_async_tx_descriptor *desc = NULL;
struct dma_chan *chan = host->chan_rx;
struct mfd_cell *cell = host->pdev->dev.platform_data;
struct tmio_mmc_data *pdata = cell->driver_data;
dma_cookie_t cookie;
int ret;
int ret, i;
bool aligned = true, multiple = true;
unsigned int align = (1 << pdata->dma->alignment_shift) - 1;

for_each_sg(sg, sg_tmp, host->sg_len, i) {
if (sg_tmp->offset & align)
aligned = false;
if (sg_tmp->length & align) {
multiple = false;
break;
}
}

if ((!aligned && (host->sg_len > 1 || sg->length > PAGE_CACHE_SIZE ||
align >= MAX_ALIGN)) || !multiple)
goto pio;

/* The only sg element can be unaligned, use our bounce buffer then */
if (!aligned) {
sg_init_one(&host->bounce_sg, host->bounce_buf, sg->length);
host->sg_ptr = &host->bounce_sg;
sg = host->sg_ptr;
}

ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_FROM_DEVICE);
if (ret > 0) {
Expand All @@ -661,6 +704,7 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
__func__, host->sg_len, ret, cookie, host->mrq);

pio:
if (!desc) {
/* DMA failed, fall back to PIO */
if (ret >= 0)
Expand All @@ -684,11 +728,39 @@ static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)

static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
{
struct scatterlist *sg = host->sg_ptr;
struct scatterlist *sg = host->sg_ptr, *sg_tmp;
struct dma_async_tx_descriptor *desc = NULL;
struct dma_chan *chan = host->chan_tx;
struct mfd_cell *cell = host->pdev->dev.platform_data;
struct tmio_mmc_data *pdata = cell->driver_data;
dma_cookie_t cookie;
int ret;
int ret, i;
bool aligned = true, multiple = true;
unsigned int align = (1 << pdata->dma->alignment_shift) - 1;

for_each_sg(sg, sg_tmp, host->sg_len, i) {
if (sg_tmp->offset & align)
aligned = false;
if (sg_tmp->length & align) {
multiple = false;
break;
}
}

if ((!aligned && (host->sg_len > 1 || sg->length > PAGE_CACHE_SIZE ||
align >= MAX_ALIGN)) || !multiple)
goto pio;

/* The only sg element can be unaligned, use our bounce buffer then */
if (!aligned) {
unsigned long flags;
void *sg_vaddr = tmio_mmc_kmap_atomic(sg, &flags);
sg_init_one(&host->bounce_sg, host->bounce_buf, sg->length);
memcpy(host->bounce_buf, sg_vaddr, host->bounce_sg.length);
tmio_mmc_kunmap_atomic(sg_vaddr, &flags);
host->sg_ptr = &host->bounce_sg;
sg = host->sg_ptr;
}

ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_TO_DEVICE);
if (ret > 0) {
Expand All @@ -709,6 +781,7 @@ static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
__func__, host->sg_len, ret, cookie, host->mrq);

pio:
if (!desc) {
/* DMA failed, fall back to PIO */
if (ret >= 0)
Expand Down Expand Up @@ -822,6 +895,10 @@ static void tmio_mmc_release_dma(struct tmio_mmc_host *host)
}
}
#else
static void tmio_check_bounce_buffer(struct tmio_mmc_host *host)
{
}

static void tmio_mmc_start_dma(struct tmio_mmc_host *host,
struct mmc_data *data)
{
Expand Down
1 change: 1 addition & 0 deletions include/linux/mfd/tmio.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ void tmio_core_mmc_clk_div(void __iomem *cnf, int shift, int state);
struct tmio_mmc_dma {
void *chan_priv_tx;
void *chan_priv_rx;
int alignment_shift;
};

/*
Expand Down

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