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mmc: sdricoh_cs: Throttle polling rate for data transfers

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Rather than to poll in a busy-loop, let's convert into using
read_poll_timeout() and insert a small delay between each polling attempts.
In particular, this avoids hogging the CPU.

Additionally, to convert to read_poll_timeout() we also need to switch from
using a specific number of polling attempts, into a specific timeout in us
instead. The previous 100000 attempts, is translated into a total timeout
of total 1s, as that seemed like reasonable value to pick.

Cc: Sascha Sommer <saschasommer@freenet.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200508095210.14123-1-ulf.hansson@linaro.org
This commit is contained in:
Ulf Hansson 2020-05-08 11:52:10 +02:00
parent 85a3f77c1b
commit eadb789765
1 changed files with 15 additions and 11 deletions
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28
drivers/mmc/host/sdricoh_cs.c
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@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/ioport.h>
#include <linux/iopoll.h>
#include <linux/scatterlist.h>
#include <pcmcia/cistpl.h>
@ -59,7 +60,7 @@ static unsigned int switchlocked;
/* timeouts */
#define CMD_TIMEOUT 100000
#define TRANSFER_TIMEOUT 100000
#define SDRICOH_DATA_TIMEOUT_US 1000000
/* list of supported pcmcia devices */
static const struct pcmcia_device_id pcmcia_ids[] = {
@ -123,21 +124,24 @@ static inline unsigned int sdricoh_readb(struct sdricoh_host *host,
return value;
}
static int sdricoh_query_status(struct sdricoh_host *host, unsigned int wanted)
static bool sdricoh_status_ok(struct sdricoh_host *host, unsigned int status,
unsigned int wanted)
{
unsigned int loop;
unsigned int status = 0;
unsigned int timeout = TRANSFER_TIMEOUT;
struct device *dev = host->dev;
for (loop = 0; loop < timeout; loop++) {
status = sdricoh_readl(host, R21C_STATUS);
sdricoh_writel(host, R2E4_STATUS_RESP, status);
if (status & wanted)
break;
return status & wanted;
}
if (loop == timeout) {
static int sdricoh_query_status(struct sdricoh_host *host, unsigned int wanted)
{
int ret;
unsigned int status = 0;
struct device *dev = host->dev;
ret = read_poll_timeout(sdricoh_readl, status,
sdricoh_status_ok(host, status, wanted),
32, SDRICOH_DATA_TIMEOUT_US, false,
host, R21C_STATUS);
if (ret) {
dev_err(dev, "query_status: timeout waiting for %x\n", wanted);
return -ETIMEDOUT;
}