[PATCH v4] mmc: Make ID freq configurable

[Hein_Tibosch]

In the latest releases of the mmc driver, the freq during initialization
is set to a fixed 400 Khz. This was reportedly too fast for several
users. As there doesn't seem to be an ideal frequency which-works-for-all,
Pierre suggested to let the driver try several frequencies.

This patch implements that idea. It will try mmc-initialization using
several frequencies from an array 400, 300, 200 and 100.
I submitted it earlier but it's now adapted to and tested with kernel
2.6.36-rc3.

In case SDIO is broken, it'll still try to detect SDMEM, also at different
freqs.

Signed-off-by: Hein Tibosch <hein_tibosch@xxxxxxxx>

---
diff -Nurp a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
--- a/drivers/mmc/core/core.c	2010-08-29 23:36:04.000000000 +0800
+++ b/drivers/mmc/core/core.c	2010-09-03 04:28:52.000000000 +0800
@@ -907,12 +907,7 @@ static void mmc_power_up(struct mmc_host
 	 */
 	mmc_delay(10);

-	if (host->f_min > 400000) {
-		pr_warning("%s: Minimum clock frequency too high for "
-				"identification mode\n", mmc_hostname(host));
-		host->ios.clock = host->f_min;
-	} else
-		host->ios.clock = 400000;
+	host->ios.clock = host->f_init;

 	host->ios.power_mode = MMC_POWER_ON;
 	mmc_set_ios(host);
@@ -1404,6 +1399,8 @@ void mmc_rescan(struct work_struct *work
 	u32 ocr;
 	int err;
 	unsigned long flags;
+	int i;
+	unsigned freqs[] = { 400000, 300000, 200000, 100000 };

 	spin_lock_irqsave(&host->lock, flags);

@@ -1443,55 +1440,64 @@ void mmc_rescan(struct work_struct *work
 	if (host->ops->get_cd && host->ops->get_cd(host) == 0)
 		goto out;

-	mmc_claim_host(host);
+	for (i = 0; i < ARRAY_SIZE(freqs); i++) {
+		mmc_claim_host(host);

-	mmc_power_up(host);
-	sdio_reset(host);
-	mmc_go_idle(host);
+		if (freqs[i] >= host->f_min)
+			host->f_init = freqs[i];
+		else if (i && freqs[i-1] <= host->f_min)
+			goto out;
+		else
+			host->f_init = host->f_min;

-	mmc_send_if_cond(host, host->ocr_avail);
+		printk ("mmc_rescan: trying %u Hz\n", host->f_init);
+		mmc_power_up(host);
+		sdio_reset(host);
+		mmc_go_idle(host);

-	/*
-	 * First we search for SDIO...
-	 */
-	err = mmc_send_io_op_cond(host, 0, &ocr);
-	if (!err) {
-		if (mmc_attach_sdio(host, ocr)) {
-			mmc_claim_host(host);
-			/* try SDMEM (but not MMC) even if SDIO is broken */
-			if (mmc_send_app_op_cond(host, 0, &ocr))
-				goto out_fail;
+		mmc_send_if_cond(host, host->ocr_avail);
+
+		/*
+		 * First we search for SDIO...
+		 */
+		err = mmc_send_io_op_cond(host, 0, &ocr);
+		if (!err) {
+			if (mmc_attach_sdio(host, ocr)) {
+				mmc_claim_host(host);
+				/* try SDMEM (but not MMC) even if SDIO is broken */
+				if (mmc_send_app_op_cond(host, 0, &ocr))
+					goto out_fail;
+
+				if (mmc_attach_sd(host, ocr))
+					mmc_power_off(host);
+			}
+			goto out;
+		}

+		/*
+		 * ...then normal SD...
+		 */
+		err = mmc_send_app_op_cond(host, 0, &ocr);
+		if (!err) {
 			if (mmc_attach_sd(host, ocr))
 				mmc_power_off(host);
+			goto out;
 		}
-		goto out;
-	}

-	/*
-	 * ...then normal SD...
-	 */
-	err = mmc_send_app_op_cond(host, 0, &ocr);
-	if (!err) {
-		if (mmc_attach_sd(host, ocr))
-			mmc_power_off(host);
-		goto out;
-	}
-
-	/*
-	 * ...and finally MMC.
-	 */
-	err = mmc_send_op_cond(host, 0, &ocr);
-	if (!err) {
-		if (mmc_attach_mmc(host, ocr))
-			mmc_power_off(host);
-		goto out;
-	}
+		/*
+		 * ...and finally MMC.
+		 */
+		err = mmc_send_op_cond(host, 0, &ocr);
+		if (!err) {
+			if (mmc_attach_mmc(host, ocr))
+				mmc_power_off(host);
+			goto out;
+		}

 out_fail:
-	mmc_release_host(host);
-	mmc_power_off(host);
-
+		mmc_release_host(host);
+		mmc_power_off(host);
+	}
 out:
 	if (host->caps & MMC_CAP_NEEDS_POLL)
 		mmc_schedule_delayed_work(&host->detect, HZ);
diff -Nurp a/include/linux/mmc/host.h b/include/linux/mmc/host.h
--- a/include/linux/mmc/host.h	2010-08-29 23:36:04.000000000 +0800
+++ b/include/linux/mmc/host.h	2010-09-03 00:52:48.000000000 +0800
@@ -123,6 +123,7 @@ struct mmc_host {
 	const struct mmc_host_ops *ops;
 	unsigned int		f_min;
 	unsigned int		f_max;
+	unsigned int		f_init;
 	u32			ocr_avail;
 	struct notifier_block	pm_notify;

---

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