Re: [PATCH v2 3/4] firmware: qcom_scm: Refactor code to support multiple download mode
From: Mukesh Ojha
Date: Fri Mar 17 2023 - 11:15:21 EST
On 3/16/2023 9:57 PM, Dmitry Baryshkov wrote:
On 03/03/2023 09:46, Mukesh Ojha wrote:
Thanks for your time in checking this..
On 3/1/2023 4:29 PM, Dmitry Baryshkov wrote:
On 01/03/2023 11:55, Mukesh Ojha wrote:
Currently on Qualcomm SoC, download_mode is enabled if
CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT is selected.
Refactor the code such that it supports multiple download
modes and drop CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT config
instead, give interface to set the download mode from
module parameter.
Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
---
Changes in v2:
- Passed download mode as parameter
- Accept human accepatable download mode string.
- enable = !!dload_mode
- Shifted module param callback to somewhere down in
the file so that it no longer need to know the
prototype of qcom_scm_set_download_mode()
- updated commit text.
drivers/firmware/Kconfig | 11 --------
drivers/firmware/qcom_scm.c | 65
++++++++++++++++++++++++++++++++++++++-------
2 files changed, 56 insertions(+), 20 deletions(-)
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index b59e304..ff7e9f3 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -215,17 +215,6 @@ config MTK_ADSP_IPC
config QCOM_SCM
tristate
-config QCOM_SCM_DOWNLOAD_MODE_DEFAULT
- bool "Qualcomm download mode enabled by default"
- depends on QCOM_SCM
- help
- A device with "download mode" enabled will upon an unexpected
- warm-restart enter a special debug mode that allows the user to
- "download" memory content over USB for offline postmortem
analysis.
- The feature can be enabled/disabled on the kernel command line.
-
- Say Y here to enable "download mode" by default.
-
config SYSFB
bool
select BOOT_VESA_SUPPORT
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index c9f1fad..ca07208 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -17,17 +17,22 @@
#include <linux/clk.h>
#include <linux/reset-controller.h>
#include <linux/arm-smccc.h>
+#include <linux/kstrtox.h>
#include "qcom_scm.h"
-static bool download_mode =
IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
-module_param(download_mode, bool, 0);
-
#define SCM_HAS_CORE_CLK BIT(0)
#define SCM_HAS_IFACE_CLK BIT(1)
#define SCM_HAS_BUS_CLK BIT(2)
#define QCOM_DOWNLOAD_MODE_MASK 0x30
+#define QCOM_DOWNLOAD_FULLDUMP 0x10
+#define QCOM_DOWNLOAD_NODUMP 0x0
+
+#define MAX_DLOAD_LEN 8
+
+static char download_mode[] = "off";
+static u32 dload_mode;
struct qcom_scm {
struct device *dev;
@@ -417,8 +422,9 @@ static int __qcom_scm_set_dload_mode(struct
device *dev, bool enable)
return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
}
-static void qcom_scm_set_download_mode(bool enable)
+static void qcom_scm_set_download_mode(u32 dload_mode)
{
+ bool enable = !!dload_mode;
bool avail;
int ret = 0;
u32 val;
@@ -438,7 +444,7 @@ static void qcom_scm_set_download_mode(bool enable)
val &= ~QCOM_DOWNLOAD_MODE_MASK;
if (enable)
- val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
+ val |= dload_mode;
ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);
} else {
@@ -1338,6 +1344,47 @@ bool qcom_scm_is_available(void)
}
EXPORT_SYMBOL(qcom_scm_is_available);
+static int set_dload_mode(const char *val, const struct
kernel_param *kp)
+{
+ int ret;
+
+ if (!strncmp(val, "full", strlen("full"))) {
+ dload_mode = QCOM_DOWNLOAD_FULLDUMP;
+ } else if (!strncmp(val, "off", strlen("off"))) {
+ dload_mode = QCOM_DOWNLOAD_NODUMP;
+ } else {
+ if (kstrtouint(val, 0, &dload_mode) ||
+ !(dload_mode == 0 || dload_mode == 1)) {
+ pr_err("unknown download mode\n");
+ return -EINVAL;
+ }
+
+ }
+
+ ret = param_set_copystring(val, kp);
+ if (ret)
+ return ret;
+
+ if (__scm)
+ qcom_scm_set_download_mode(dload_mode);
+
+ return 0;
+}
+
+static const struct kernel_param_ops dload_mode_param_ops = {
+ .set = set_dload_mode,
+ .get = param_get_string,
Please follow the param_get_bool approach and return sanitized data
here. In other words, "full" / "none" depending on the dload_mode
instead of storing the passed string and returning it later.
This could be done.
+};
+
+static struct kparam_string dload_mode_param = {
+ .string = download_mode,
+ .maxlen = MAX_DLOAD_LEN,
I think writing "full" to this param might overwrite some kernel
data. "00000000" should be even worse.
There is check in param_set_copystring() which would avoid that.
No. The check will validate the value's length against MAX_DLOAD_LEN.
But it will not safeguard your code. download_mode's size is less than
MAX_DLOAD_LEN.
Oops !! you are right..,
Will fix it in v3.
-Mukesh