Commit eadb7897 authored by Ulf Hansson's avatar Ulf Hansson
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mmc: sdricoh_cs: Throttle polling rate for data transfers 



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: default avatarUlf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200508095210.14123-1-ulf.hansson@linaro.org
parent 85a3f77c

drivers/mmc/host/sdricoh_cs.c

+15 −11
Original line number Diff line number Diff line
@@ -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 bool sdricoh_status_ok(struct sdricoh_host *host, unsigned int status,

			      unsigned int wanted)

{

	sdricoh_writel(host, R2E4_STATUS_RESP, status);

	return status & wanted;

}



static int sdricoh_query_status(struct sdricoh_host *host, unsigned int wanted)

{

	unsigned int loop;

	int ret;

	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;

	}



	if (loop == timeout) {

	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;

	}