On 05/26, Bjorn Andersson wrote: > In order to aid post-mortem debugging the Qualcomm platforms provides a > "memory download mode", where the boot loader will provide an interface > for custom tools to "download" the content of RAM to a host machine. > > The mode is triggered by writing a magic value somehwere in RAM, that is > read in the boot code path after a warm-restart. Two mechanism for > setting this magic value are supported in modern platforms; a direct SCM > call to enable the mode or through a secure io write of a magic value. > > In order for a normal reboot not to trigger "download mode" the magic > must be cleared during a clean reboot. > > Download mode has to be enabled by including qcom_scm.download_mode=1 on > the command line. Why the kernel command line parameter? If we keep the kernel command line param, perhaps we can also gain a config option to make it default enabled or default disabled so that we don't have to specify it on the commandline to get the feature all the time. > > diff --git a/Documentation/devicetree/bindings/firmware/qcom,scm.txt b/Documentation/devicetree/bindings/firmware/qcom,scm.txt > index 20f26fbce875..388817d1d00e 100644 > --- a/Documentation/devicetree/bindings/firmware/qcom,scm.txt > +++ b/Documentation/devicetree/bindings/firmware/qcom,scm.txt > @@ -18,6 +18,8 @@ Required properties: > * Core, iface, and bus clocks required for "qcom,scm" > - clock-names: Must contain "core" for the core clock, "iface" for the interface > clock and "bus" for the bus clock per the requirements of the compatible. > +- qcom,dload-mode-addr: Specifies the address (2 cells) for the download mode > + magic (optional) Was it decided that reg was improper? Or a phandle to a node that has a reg property? > > Example for MSM8916: > > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c > index e18d63935648..98f4747acddb 100644 > --- a/drivers/firmware/qcom_scm.c > +++ b/drivers/firmware/qcom_scm.c > @@ -19,6 +19,7 @@ > #include <linux/cpumask.h> > #include <linux/export.h> > #include <linux/dma-mapping.h> > +#include <linux/module.h> > #include <linux/types.h> > #include <linux/qcom_scm.h> > #include <linux/of.h> > @@ -28,6 +29,9 @@ > > #include "qcom_scm.h" > > +static bool download_mode; > +module_param(download_mode, bool, 0700); 0700? Not 0600? And what if we have it == 1 on the command line and then write 0 at runtime with module param? Shouldn't we handle that with a callback and turn off download mode there? Otherwise when we reboot we will reboot into download mode? > + > #define SCM_HAS_CORE_CLK BIT(0) > #define SCM_HAS_IFACE_CLK BIT(1) > #define SCM_HAS_BUS_CLK BIT(2) > @@ -365,6 +393,7 @@ static int qcom_scm_probe(struct platform_device *pdev) > struct qcom_scm *scm; > unsigned long clks; > int ret; > + u64 val; > > scm = devm_kzalloc(&pdev->dev, sizeof(*scm), GFP_KERNEL); > if (!scm) > @@ -418,9 +447,22 @@ static int qcom_scm_probe(struct platform_device *pdev) > > __qcom_scm_init(); > > + ret = of_property_read_u64(pdev->dev.of_node, "qcom,dload-mode-addr", &val); > + if (!ret) > + scm->dload_mode_addr = val; How about: of_property_read_u64(pdev->dev.of_node, "qcom,dload-mode-addr", &scm->dload_mode_addr) > + > + if (download_mode) > + qcom_scm_set_download_mode(true); > + > return 0; > } > > +void qcom_scm_shutdown(struct platform_device *pdev) static? > +{ > + if (download_mode) > + qcom_scm_set_download_mode(false); > +} > + -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html