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authorIdo Yariv <ido@wizery.com>2012-03-11 23:39:59 +0200
committerChris Ball <cjb@laptop.org>2012-03-27 12:20:11 -0400
commitee698f503442741ca394d55c77b61c9080537686 (patch)
treeca5e2fe1ce47f1a7789050e469c2c0504bbea297
parentbe7b5622e608189894c2c440c3fb0138f122071f (diff)
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mmc: davinci: Poll status for small size transfers
For small size non-dma sdio transactions, it is sometimes better to poll the mmc host and avoid interrupts altogether. Polling lowers the number of interrupts and context switches. Tests have shown that for small transactions, only a few polling iterations are needed, so this is worth while. Signed-off-by: Ido Yariv <ido@wizery.com> Tested-by: Rajashekhara, Sudhakar <sudhakar.raj@ti.com> Signed-off-by: Chris Ball <cjb@laptop.org>
-rw-r--r--drivers/mmc/host/davinci_mmc.c29
1 files changed, 28 insertions, 1 deletions
diff --git a/drivers/mmc/host/davinci_mmc.c b/drivers/mmc/host/davinci_mmc.c
index 1e076fb06ac3..c1f3673ae1ef 100644
--- a/drivers/mmc/host/davinci_mmc.c
+++ b/drivers/mmc/host/davinci_mmc.c
@@ -160,6 +160,16 @@ module_param(rw_threshold, uint, S_IRUGO);
MODULE_PARM_DESC(rw_threshold,
"Read/Write threshold. Default = 32");
+static unsigned poll_threshold = 128;
+module_param(poll_threshold, uint, S_IRUGO);
+MODULE_PARM_DESC(poll_threshold,
+ "Polling transaction size threshold. Default = 128");
+
+static unsigned poll_loopcount = 32;
+module_param(poll_loopcount, uint, S_IRUGO);
+MODULE_PARM_DESC(poll_loopcount,
+ "Maximum polling loop count. Default = 32");
+
static unsigned __initdata use_dma = 1;
module_param(use_dma, uint, 0);
MODULE_PARM_DESC(use_dma, "Whether to use DMA or not. Default = 1");
@@ -193,6 +203,7 @@ struct mmc_davinci_host {
bool use_dma;
bool do_dma;
bool sdio_int;
+ bool active_request;
/* Scatterlist DMA uses one or more parameter RAM entries:
* the main one (associated with rxdma or txdma) plus zero or
@@ -219,6 +230,7 @@ struct mmc_davinci_host {
#endif
};
+static irqreturn_t mmc_davinci_irq(int irq, void *dev_id);
/* PIO only */
static void mmc_davinci_sg_to_buf(struct mmc_davinci_host *host)
@@ -376,7 +388,20 @@ static void mmc_davinci_start_command(struct mmc_davinci_host *host,
writel(cmd->arg, host->base + DAVINCI_MMCARGHL);
writel(cmd_reg, host->base + DAVINCI_MMCCMD);
- writel(im_val, host->base + DAVINCI_MMCIM);
+
+ host->active_request = true;
+
+ if (!host->do_dma && host->bytes_left <= poll_threshold) {
+ u32 count = poll_loopcount;
+
+ while (host->active_request && count--) {
+ mmc_davinci_irq(0, host);
+ cpu_relax();
+ }
+ }
+
+ if (host->active_request)
+ writel(im_val, host->base + DAVINCI_MMCIM);
}
/*----------------------------------------------------------------------*/
@@ -915,6 +940,7 @@ mmc_davinci_xfer_done(struct mmc_davinci_host *host, struct mmc_data *data)
if (!data->stop || (host->cmd && host->cmd->error)) {
mmc_request_done(host->mmc, data->mrq);
writel(0, host->base + DAVINCI_MMCIM);
+ host->active_request = false;
} else
mmc_davinci_start_command(host, data->stop);
}
@@ -942,6 +968,7 @@ static void mmc_davinci_cmd_done(struct mmc_davinci_host *host,
cmd->mrq->cmd->retries = 0;
mmc_request_done(host->mmc, cmd->mrq);
writel(0, host->base + DAVINCI_MMCIM);
+ host->active_request = false;
}
}