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Date: Wed, 1 Mar 2023 12:59:18 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Mukesh Ojha <quic_mojha@...cinc.com>, agross@...nel.org,
andersson@...nel.org, konrad.dybcio@...aro.org
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] firmware: qcom_scm: Refactor code to support
multiple download mode
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@...cinc.com>
> ---
> 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.
> +};
> +
> +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.
> +};
> +
> +module_param_cb(download_mode, &dload_mode_param_ops, &dload_mode_param, 0644);
> +MODULE_PARM_DESC(download_mode,
> + "Download mode: off/full or 0/1/off/on for existing users");
Nit: on is not supported even for existing users.
> +
> static int qcom_scm_probe(struct platform_device *pdev)
> {
> struct qcom_scm *scm;
> @@ -1418,12 +1465,12 @@ static int qcom_scm_probe(struct platform_device *pdev)
> __get_convention();
>
> /*
> - * If requested enable "download mode", from this point on warmboot
> + * If download mode is requested, from this point on warmboot
> * will cause the boot stages to enter download mode, unless
> * disabled below by a clean shutdown/reboot.
> */
> - if (download_mode)
> - qcom_scm_set_download_mode(true);
> + if (dload_mode)
> + qcom_scm_set_download_mode(dload_mode);
>
> return 0;
> }
> @@ -1431,7 +1478,7 @@ static int qcom_scm_probe(struct platform_device *pdev)
> static void qcom_scm_shutdown(struct platform_device *pdev)
> {
> /* Clean shutdown, disable download mode to allow normal restart */
> - qcom_scm_set_download_mode(false);
> + qcom_scm_set_download_mode(QCOM_DOWNLOAD_NODUMP);
> }
>
> static const struct of_device_id qcom_scm_dt_match[] = {
--
With best wishes
Dmitry
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