feature(sdio): allow to enable internal pullups of the SDIO host and slave as a debug feature

NOTE: the internal pullups are not totally reliable, please do add external pullups on your bus.

components/driver/include/driver/sdio_slave.h

@@ -20,7 +20,7 @@
 #include "esp_err.h"
 #include "rom/queue.h"
 
-#include "soc/host_reg.h"
+#include "soc/sdio_slave_periph.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -71,6 +71,23 @@ typedef struct {
                             ///< All data that do not fully fill a buffer is still counted as one buffer. E.g. 10 bytes data costs 2 buffers if the size is 8 bytes per buffer.
                             ///< Buffer size of the slave pre-defined between host and slave before communication. All receive buffer given to the driver should be larger than this.
     sdio_event_cb_t     event_cb;           ///< when the host interrupts slave, this callback will be called with interrupt number (0-7).
+    uint32_t            flags; ///< Features to be enabled for the slave, combinations of ``SDIO_SLAVE_FLAG_*``.
+#define SDIO_SLAVE_FLAG_DAT2_DISABLED       BIT(0)      /**< It is required by the SD specification that all 4 data 
+        lines should be used and pulled up even in 1-bit mode or SPI mode. However, as a feature, the user can speicfy 
+        this flag to make use of DAT2 pin in 1-bit mode. Note that the host cannot read CCCR registers to know we don't 
+        support 4-bit mode anymore, please do this at your own risk.
+        */
+#define SDIO_SLAVE_FLAG_HOST_INTR_DISABLED  BIT(1)      /**< The DAT1 line is used as the interrupt line in SDIO        
+        protocol. However, as a feature, the user can speicfy this flag to make use of DAT1 pin of the slave in 1-bit 
+        mode. Note that the host has to do polling to the interrupt registers to know whether there are interrupts from
+        the slave. And it cannot read CCCR registers to know we don't support 4-bit mode anymore, please do this at 
+        your own risk.
+        */
+#define SDIO_SLAVE_FLAG_INTERNAL_PULLUP     BIT(2)      /**< Enable internal pullups for enabled pins. It is required 
+        by the SD specification that all the 4 data lines should be pulled up even in 1-bit mode or SPI mode. Note that 
+        the internal pull-ups are not sufficient for stable communication, please do connect external pull-ups on the 
+        bus. This is only for example and debug use.
+        */
 } sdio_slave_config_t;
 
 /** Handle of a receive buffer, register a handle by calling ``sdio_slave_recv_register_buf``. Use the handle to load the buffer to the

components/driver/include/driver/sdmmc_host.h

@@ -55,6 +55,12 @@ typedef struct {
     gpio_num_t gpio_cd;     ///< GPIO number of card detect signal
     gpio_num_t gpio_wp;     ///< GPIO number of write protect signal
     uint8_t width;          ///< Bus width used by the slot (might be less than the max width supported)
+    uint32_t flags;         ///< Features used by this slot
+#define SDMMC_SLOT_FLAG_INTERNAL_PULLUP  BIT(0) 
+        /**< Enable internal pullups on enabled pins. The internal pullups
+         are insufficient however, please make sure external pullups are
+         connected on the bus. This is for debug / example purpose only.
+         */
 } sdmmc_slot_config_t;
 
 #define SDMMC_SLOT_NO_CD      ((gpio_num_t) -1)     ///< indicates that card detect line is not used
@@ -68,6 +74,7 @@ typedef struct {
     .gpio_cd = SDMMC_SLOT_NO_CD, \
     .gpio_wp = SDMMC_SLOT_NO_WP, \
     .width   = SDMMC_SLOT_WIDTH_DEFAULT, \
+    .flags = 0, \
 }
 
 /**
@@ -199,6 +206,23 @@ esp_err_t sdmmc_host_io_int_wait(int slot, TickType_t timeout_ticks);
  */
 esp_err_t sdmmc_host_deinit();
 
+/**
+ * @brief Enable the pull-ups of sd pins.
+ * 
+ * @note You should always place actual pullups on the lines instead of using
+ * this function. Internal pullup resistance are high and not sufficient, may
+ * cause instability in products. This is for debug or examples only.
+ * 
+ * @param slot Slot to use, normally set it to 1.
+ * @param width Bit width of your configuration, 1 or 4.
+ * 
+ * @return
+ *      - ESP_OK: if success
+ *      - ESP_ERR_INVALID_ARG: if configured width larger than maximum the slot can
+ *              support
+ */
+esp_err_t sdmmc_host_pullup_en(int slot, int width);
+
 #ifdef __cplusplus
 }
 #endif