bus: ti-sysc: Check for lost context in sysc_reinit_module()

There is no need to restore context if it was not lost. Let's add a new
function sysc_check_context() to check for lost context. To make use of it,
we need to save the sysconfig register status on enable and disable.

Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c
index efd8f0f..9e95834 100644 (file)
--- a/drivers/bus/ti-sysc.c
+++ b/drivers/bus/ti-sysc.c
@@ -132,6 +132,7 @@ struct sysc {
        struct ti_sysc_cookie cookie;
        const char *name;
        u32 revision;
+       u32 sysconfig;
        unsigned int reserved:1;
        unsigned int enabled:1;
        unsigned int needs_resume:1;
@@ -1135,7 +1136,8 @@ set_midle:
        best_mode = fls(ddata->cfg.midlemodes) - 1;
        if (best_mode > SYSC_IDLE_MASK) {
                dev_err(dev, "%s: invalid midlemode\n", __func__);
-               return -EINVAL;
+               error = -EINVAL;
+               goto save_context;
        }
 
        if (ddata->cfg.quirks & SYSC_QUIRK_SWSUP_MSTANDBY)
@@ -1153,13 +1155,16 @@ set_autoidle:
                sysc_write_sysconfig(ddata, reg);
        }
 
-       /* Flush posted write */
-       sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
+       error = 0;
+
+save_context:
+       /* Save context and flush posted write */
+       ddata->sysconfig = sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
 
        if (ddata->module_enable_quirk)
                ddata->module_enable_quirk(ddata);
 
-       return 0;
+       return error;
 }
 
 static int sysc_best_idle_mode(u32 idlemodes, u32 *best_mode)
@@ -1216,8 +1221,10 @@ static int sysc_disable_module(struct device *dev)
 set_sidle:
        /* Set SIDLE mode */
        idlemodes = ddata->cfg.sidlemodes;
-       if (!idlemodes || regbits->sidle_shift < 0)
-               return 0;
+       if (!idlemodes || regbits->sidle_shift < 0) {
+               ret = 0;
+               goto save_context;
+       }
 
        if (ddata->cfg.quirks & SYSC_QUIRK_SWSUP_SIDLE) {
                best_mode = SYSC_IDLE_FORCE;
@@ -1225,7 +1232,8 @@ set_sidle:
                ret = sysc_best_idle_mode(idlemodes, &best_mode);
                if (ret) {
                        dev_err(dev, "%s: invalid sidlemode\n", __func__);
-                       return ret;
+                       ret = -EINVAL;
+                       goto save_context;
                }
        }
 
@@ -1236,10 +1244,13 @@ set_sidle:
                reg |= 1 << regbits->autoidle_shift;
        sysc_write_sysconfig(ddata, reg);
 
-       /* Flush posted write */
-       sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
+       ret = 0;
 
-       return 0;
+save_context:
+       /* Save context and flush posted write */
+       ddata->sysconfig = sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
+
+       return ret;
 }
 
 static int __maybe_unused sysc_runtime_suspend_legacy(struct device *dev,
@@ -1377,13 +1388,40 @@ err_allow_idle:
        return error;
 }
 
+/*
+ * Checks if device context was lost. Assumes the sysconfig register value
+ * after lost context is different from the configured value. Only works for
+ * enabled devices.
+ *
+ * Eventually we may want to also add support to using the context lost
+ * registers that some SoCs have.
+ */
+static int sysc_check_context(struct sysc *ddata)
+{
+       u32 reg;
+
+       if (!ddata->enabled)
+               return -ENODATA;
+
+       reg = sysc_read(ddata, ddata->offsets[SYSC_SYSCONFIG]);
+       if (reg == ddata->sysconfig)
+               return 0;
+
+       return -EACCES;
+}
+
 static int sysc_reinit_module(struct sysc *ddata, bool leave_enabled)
 {
        struct device *dev = ddata->dev;
        int error;
 
-       /* Disable target module if it is enabled */
        if (ddata->enabled) {
+               /* Nothing to do if enabled and context not lost */
+               error = sysc_check_context(ddata);
+               if (!error)
+                       return 0;
+
+               /* Disable target module if it is enabled */
                error = sysc_runtime_suspend(dev);
                if (error)
                        dev_warn(dev, "reinit suspend failed: %i\n", error);