From b59b1c0040a052d5838d27047fab4bd19efb277a Mon Sep 17 00:00:00 2001
From: Alex Zhao <zzc@rock-chips.com>
Date: Wed, 6 Jan 2021 09:47:33 +0800
Subject: [PATCH] mmc: add a file to debugfs for changing host max clock at
 runtime

Usage is as follows:

rk3566_rgo:/ # cat /sys/kernel/debug/mmc1/max_clock
150000000

rk3566_rgo:/ # echo 200000000 > /sys/kernel/debug/mmc1/max_clock
rk3566_rgo:/ # cat /sys/kernel/debug/mmc1/max_clock
200000000
rk3566_rgo:/ # echo 200000000 >  /sys/kernel/debug/mmc1/clock

rk3566_rgo:/ # dmesg -c
[  285.884348] mmc_host mmc1: Bus speed (slot 0) = 198000000Hz (slot req 200000000Hz, actual 198000000HZ div = 0)

Signed-off-by: Alex Zhao <zzc@rock-chips.com>
Change-Id: I7ac9649b231c50b0c6c066407e28954e8c94510c
---
 drivers/mmc/core/debugfs.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index d2275c5a2311..4ee261d9580e 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -225,6 +225,31 @@ static int mmc_clock_opt_set(void *data, u64 val)
 DEFINE_SIMPLE_ATTRIBUTE(mmc_clock_fops, mmc_clock_opt_get, mmc_clock_opt_set,
 	"%llu\n");
 
+static int mmc_max_clock_opt_get(void *data, u64 *val)
+{
+	struct mmc_host *host = data;
+
+	*val = host->f_max;
+
+	return 0;
+}
+
+static int mmc_max_clock_opt_set(void *data, u64 val)
+{
+	struct mmc_host *host = data;
+
+	/* We need this check due to input value is u64 */
+	if (val != 0 && (val > UHS_SDR104_MAX_DTR || val < host->f_min))
+		return -EINVAL;
+
+	host->f_max = (unsigned int) val;
+
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(mmc_max_clock_fops, mmc_max_clock_opt_get, mmc_max_clock_opt_set,
+	"%llu\n");
+
 void mmc_add_host_debugfs(struct mmc_host *host)
 {
 	struct dentry *root;
@@ -253,6 +278,9 @@ void mmc_add_host_debugfs(struct mmc_host *host)
 			&mmc_clock_fops))
 		goto err_node;
 
+	debugfs_create_file_unsafe("max_clock", S_IRUSR | S_IWUSR, root, host,
+				   &mmc_max_clock_fops);
+
 #ifdef CONFIG_FAIL_MMC_REQUEST
 	if (fail_request)
 		setup_fault_attr(&fail_default_attr, fail_request);