Automatically acquire the CS lock when talking to the SD card

1 files changed, 12 insertions, 3 deletions

diff --git a/main/storage.cpp b/main/storage.cpp
index e1f6f386..d2f88894 100644
--- a/main/storage.cpp
+++ b/main/storage.cpp
@@ -28,7 +28,6 @@ SdStorage::~SdStorage() {}
 SdStorage::Error SdStorage::Acquire(void) {
   // Acquiring the bus will also flush the mux switch change.
   gpio_->set_pin(GpioExpander::SD_MUX_SWITCH, GpioExpander::SD_MUX_ESP);
-  auto lock = gpio_->AcquireSpiBus(GpioExpander::SD_CARD);
 
   // Now we can init the driver and set up the SD card into SPI mode.
   sdspi_host_init();
@@ -44,6 +43,18 @@ SdStorage::Error SdStorage::Acquire(void) {
   ESP_ERROR_CHECK(sdspi_host_init_device(&config, &handle_));
 
   host_ = sdmmc_host_t SDSPI_HOST_DEFAULT();
+
+  // We manage the CS pin ourselves via the GPIO expander. To do this safely in
+  // a multithreaded environment, we wrap the ESP IDF do_transaction function
+  // with our own that acquires the CS mutex for the duration of the SPI
+  // transaction.
+  auto src = host_.do_transaction;
+  sdspi::do_transaction_wrapper = [=](sdspi_dev_handle_t handle, sdmmc_command_t *cmd) -> esp_err_t {
+    auto lock = gpio_->AcquireSpiBus(GpioExpander::SD_CARD);
+    return src(handle, cmd);
+  };
+  host_.do_transaction = &sdspi::do_transaction;
+
   host_.slot = handle_;
   // Will return ESP_ERR_INVALID_RESPONSE if there is no card
   esp_err_t err = sdmmc_card_init(&host_, &card_);
@@ -66,8 +77,6 @@ SdStorage::Error SdStorage::Acquire(void) {
 }
 
 void SdStorage::Release(void) {
-  auto lock = gpio_->AcquireSpiBus(GpioExpander::SD_CARD);
-
   // Unmount and unregister the filesystem
   f_unmount("");
   ff_diskio_register(fs_->pdrv, NULL);