mmc: debugfs: Allow host caps to be modified

During board verification, there is a need to test the various supported
eMMC/SD speed modes.  However, since the framework chooses the best mode
supported by the card and the host controller's caps, this currently
necessitates changing the devicetree for every iteration.

Allow the various speed mode host capabilities to be modified via
debugfs in order to allow easier hardware verification.  The values to
be written are the raw MMC_CAP* values from include/linux/mmc/host.h.
This is rather low-level, and these defines are not guaranteed to be
stable, but it is perhaps good enough for the intended use case.

MMC_CAP_AGGRESSIVE_PM can also be set, in order to be able to
re-initialize the card without having to physically remove and re-insert
it.

 /sys/kernel/debug/mmc0# grep timing ios
 timing spec:	9 (mmc HS200)

 // Turn on MMC_CAP_AGGRESSIVE_PM and re-trigger runtime suspend
 /sys/kernel/debug/mmc0# echo $(($(cat caps) | (1 << 7))) > caps
 /sys/kernel/debug/mmc0# echo on > /sys/bus/mmc/devices/mmc0\:0001/power/control
 /sys/kernel/debug/mmc0# echo auto > /sys/bus/mmc/devices/mmc0\:0001/power/control

 // MMC_CAP2_HS200_1_8V_SDR
 /sys/kernel/debug/mmc0# echo $(($(cat caps2) & ~(1 << 5))) > caps2
 /sys/kernel/debug/mmc0# echo on > /sys/bus/mmc/devices/mmc0\:0001/power/control
 /sys/kernel/debug/mmc0# grep timing ios
 timing spec:	8 (mmc DDR52)

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20230929-mmc-caps-v2-2-11a4c2d94f15@axis.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 49 insertions, 2 deletions

diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index 2c97b94aab2344..1642ea72d22c5c 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -12,9 +12,12 @@
 #include <linux/slab.h>
 #include <linux/stat.h>
 #include <linux/fault-inject.h>
+#include <linux/time.h>
 
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
+#include <linux/mmc/mmc.h>
+#include <linux/mmc/sd.h>
 
 #include "core.h"
 #include "card.h"
@@ -298,6 +301,49 @@ static const struct file_operations mmc_err_stats_fops = {
 	.release = single_release,
 };
 
+static int mmc_caps_get(void *data, u64 *val)
+{
+	*val = *(u32 *)data;
+	return 0;
+}
+
+static int mmc_caps_set(void *data, u64 val)
+{
+	u32 *caps = data;
+	u32 diff = *caps ^ val;
+	u32 allowed = MMC_CAP_AGGRESSIVE_PM |
+		      MMC_CAP_SD_HIGHSPEED |
+		      MMC_CAP_MMC_HIGHSPEED |
+		      MMC_CAP_UHS |
+		      MMC_CAP_DDR;
+
+	if (diff & ~allowed)
+		return -EINVAL;
+
+	*caps = val;
+
+	return 0;
+}
+
+static int mmc_caps2_set(void *data, u64 val)
+{
+	u32 allowed = MMC_CAP2_HSX00_1_8V | MMC_CAP2_HSX00_1_2V;
+	u32 *caps = data;
+	u32 diff = *caps ^ val;
+
+	if (diff & ~allowed)
+		return -EINVAL;
+
+	*caps = val;
+
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(mmc_caps_fops, mmc_caps_get, mmc_caps_set,
+			 "0x%08llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(mmc_caps2_fops, mmc_caps_get, mmc_caps2_set,
+			 "0x%08llx\n");
+
 void mmc_add_host_debugfs(struct mmc_host *host)
 {
 	struct dentry *root;
@@ -306,8 +352,9 @@ void mmc_add_host_debugfs(struct mmc_host *host)
 	host->debugfs_root = root;
 
 	debugfs_create_file("ios", S_IRUSR, root, host, &mmc_ios_fops);
-	debugfs_create_x32("caps", S_IRUSR, root, &host->caps);
-	debugfs_create_x32("caps2", S_IRUSR, root, &host->caps2);
+	debugfs_create_file("caps", 0600, root, &host->caps, &mmc_caps_fops);
+	debugfs_create_file("caps2", 0600, root, &host->caps2,
+			    &mmc_caps2_fops);
 	debugfs_create_file_unsafe("clock", S_IRUSR | S_IWUSR, root, host,
 				   &mmc_clock_fops);