fix: Pi 4 Bluetooth - hold RTS deasserted across BT_ON power-on, require Read Local Version to sync, mini UART no flow control first

kernel/src/Drivers/Platform/RpiFirmware.cpp

@@ -48,6 +48,8 @@ namespace Drivers::Platform::RpiFirmware {
     static constexpr uint32_t TAG_GET_CLOCK_RATE  = 0x00030002;
     static constexpr uint32_t TAG_GET_GPIO_STATE  = 0x00030041;
     static constexpr uint32_t TAG_SET_GPIO_STATE  = 0x00038041;
+    static constexpr uint32_t TAG_GET_GPIO_CONFIG = 0x00030043;
+    static constexpr uint32_t TAG_SET_GPIO_CONFIG = 0x00038043;
 
     // The VideoCore sees the first GiB of SDRAM at bus address 0xC0000000
     // (the uncached alias), and nothing above it, so the message buffer
@@ -199,18 +201,28 @@ namespace Drivers::Platform::RpiFirmware {
         g_buffer[words++] = 0;                    // end tag
         g_buffer[0] = words * 4;
 
+        // The firmware does not set the response bit for every tag: the
+        // expander GPIO tags answer through value[0] alone and leave the
+        // status word 0. Linux checks only the message code, so do the same
+        // and take the whole value buffer back when the bit is missing; each
+        // caller validates the values it gets.
         int result = -1;
-        if (Call()) {
-            uint32_t status = g_buffer[valueStart - 1];
-            if (status & TAG_RESPONSE) {
-                uint32_t length = status & ~TAG_RESPONSE;
-                uint32_t copy = (length + 3) / 4;
-                if (copy > valueWords) copy = valueWords;
-                for (uint32_t i = 0; i < copy; i++) values[i] = g_buffer[valueStart + i];
-                result = (int)length;
-            }
+        bool answered = Call();
+        uint32_t status = g_buffer[valueStart - 1];
+        if (answered) {
+            uint32_t length = (status & TAG_RESPONSE) ? status & ~TAG_RESPONSE : valueWords * 4;
+            uint32_t copy = (length + 3) / 4;
+            if (copy > valueWords) copy = valueWords;
+            for (uint32_t i = 0; i < copy; i++) values[i] = g_buffer[valueStart + i];
+            result = (int)length;
         }
+        uint32_t code = g_buffer[1];
         g_lock.Release();
+
+        if (result < 0) {
+            KernelLogStream(WARNING, "RpiFw") << "Property tag 0x" << base::hex << (uint64_t)tag
+                << " failed: message code 0x" << (uint64_t)code << base::dec;
+        }
         return result;
     }
 
@@ -228,6 +240,19 @@ namespace Drivers::Platform::RpiFirmware {
         return PropertyCall(TAG_SET_GPIO_STATE, v, 2) >= 4 && v[0] == 0;
     }
 
+    // As Linux's rpi_exp_gpio_dir_out: keep the line's polarity, make it an
+    // output driving `high`. A line the firmware still has as an input
+    // refuses SET_GPIO_STATE.
+    bool SetGpioOutput(uint32_t gpio, bool high) {
+        uint32_t polarity = 0;
+        uint32_t cfg[5] = { gpio, 0, 0, 0, 0 };   // gpio, direction, polarity, term_en, term_pull_up
+        if (PropertyCall(TAG_GET_GPIO_CONFIG, cfg, 5) >= 12 && cfg[0] == 0) polarity = cfg[2];
+
+        uint32_t v[6] = { gpio, 1 /* output */, polarity, 0, 0, high ? 1u : 0u };
+        if (PropertyCall(TAG_SET_GPIO_CONFIG, v, 6) < 4 || v[0] != 0) return false;
+        return true;
+    }
+
     bool GetGpioState(uint32_t gpio, bool& high) {
         uint32_t v[2] = { gpio, 0 };
         if (PropertyCall(TAG_GET_GPIO_STATE, v, 2) < 8 || v[0] != 0) return false;