[PATCH v3 3/3] mmc: davinci: get SG segment limits with dma_get_slave_sg_caps()

Matt Porter
2013-02-04T19:46:34Z

Replace the hardcoded values used to set max_segs/max_seg_size with
a dma_get_slave_sg_caps() query to the dmaengine driver.

Signed-off-by: Matt Porter <mporter@ti.com>
---
drivers/mmc/host/davinci_mmc.c | 37 ++++++++---------------------
include/linux/platform_data/mmc-davinci.h | 3 ---
2 files changed, 10 insertions(+), 30 deletions(-)

diff --git a/drivers/mmc/host/davinci_mmc.c b/drivers/mmc/host/davinci_mmc.c
index 2063677..583cbd0 100644
--- a/drivers/mmc/host/davinci_mmc.c
+++ b/drivers/mmc/host/davinci_mmc.c
@@ -144,18 +144,6 @@
/* MMCSD Init clock in Hz in opendrain mode */
#define MMCSD_INIT_CLOCK 200000

-/*
- * One scatterlist dma "segment" is at most MAX_CCNT rw_threshold units,
- * and we handle up to MAX_NR_SG segments. MMC_BLOCK_BOUNCE kicks in only
- * for drivers with max_segs == 1, making the segments bigger (64KB)
- * 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 MAX_NR_SG 16
-
static unsigned rw_threshold = 32;
module_param(rw_threshold, uint, S_IRUGO);
MODULE_PARM_DESC(rw_threshold,
@@ -216,8 +204,6 @@ 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
@@ -1165,6 +1151,7 @@ static int __init davinci_mmcsd_probe(struct platform_device *pdev)
struct resource *r, *mem = NULL;
int ret = 0, irq = 0;
size_t mem_size;
+ struct dma_slave_sg_caps *dma_sg_caps;

/* REVISIT: when we're fully converted, fail if pdata is NULL */

@@ -1214,12 +1201,6 @@ 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->mmc_irq = irq;
host->sdio_irq = platform_get_irq(pdev, 1);
@@ -1248,14 +1229,16 @@ static int __init davinci_mmcsd_probe(struct platform_device *pdev)
mmc->caps |= pdata->caps;
mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;

- /* With no iommu coalescing pages, each phys_seg is a hw_seg.
- * Each hw_seg uses one EDMA parameter RAM slot, always one
- * channel and then usually some linked slots.
- */
- mmc->max_segs = MAX_NR_SG;
+ /* Just check one channel for the DMA SG limits */
+ dma_sg_caps = dma_get_slave_sg_caps(
+ host->dma_tx,
+ DMA_SLAVE_BUSWIDTH_4_BYTES,
+ rw_threshold / DMA_SLAVE_BUSWIDTH_4_BYTES);

- /* EDMA limit per hw segment (one or two MBytes) */
- mmc->max_seg_size = MAX_CCNT * rw_threshold;
+ if (dma_sg_caps) {
+ mmc->max_segs = dma_sg_caps->max_seg_nr;
+ mmc->max_seg_size = dma_sg_caps->max_seg_len;
+ }

/* MMC/SD controller limits for multiblock requests */
mmc->max_blk_size = 4095; /* BLEN is 12 bits */
diff --git a/include/linux/platform_data/mmc-davinci.h b/include/linux/platform_data/mmc-davinci.h
index 5ba6b22..6910209 100644
--- a/include/linux/platform_data/mmc-davinci.h
+++ b/include/linux/platform_data/mmc-davinci.h
@@ -25,9 +25,6 @@ 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);

--
1.7.9.5