spi: fix the crash when callbacks are not in the IRAM

Introduced in 9c23b8e5 and 4f87a62f. To get higher speed, menuconfig
options are added to put ISR and other functions into the IRAM.  The
interrupt flag ESP_INTR_FLAG_IRAM is also mistakenly set when the ISR is
put into the IRAM. However callbacks, which are wrote by the user, are
called in the master and slave ISR. The user may not be aware of that
these callbacks are not disabled during flash operations. Any cache miss
during flash operation will cause panic.

Essentially IRAM functions and intrrupt flag ESP_INTR_FLAG_IRAM are
different, the latter means not disabling the ISR during flash
operations.  New bus_config flag intr_flags is offered to help set the
interrupt attribute, including priority level, SHARED, IRAM (not
disabled during flash operations).  It introduced a small BREAK to
IDFv3.1 (but the same as IDFv3.0) that the user has to manually set IRAM
flag now (therefore he's aware of the IRAM thing) to void the ISR being
disabled during flash operations.

components/driver/Kconfig

@@ -41,8 +41,10 @@ config SPI_MASTER_ISR_IN_IRAM
     bool "Place SPI master ISR function into IRAM"
     default y
     help
-        Place the SPI master ISR in to IRAM to avoid possibly cache miss, or
+        Place the SPI master ISR in to IRAM to avoid possible cache miss.
-        being disabled during flash writing access.
+
+        Also you can forbid the ISR being disabled during flash writing
+        access, by add ESP_INTR_FLAG_IRAM when initializing the driver.
 
 config SPI_SLAVE_IN_IRAM
     bool "Place transmitting functions of SPI slave into IRAM"
@@ -61,8 +63,10 @@ config SPI_SLAVE_ISR_IN_IRAM
     bool "Place SPI slave ISR function into IRAM"
     default y
     help
-        Place the SPI slave ISR in to IRAM to avoid possibly cache miss, or
+        Place the SPI slave ISR in to IRAM to avoid possible cache miss.
-        being disabled during flash writing access.
+
+        Also you can forbid the ISR being disabled during flash writing
+        access, by add ESP_INTR_FLAG_IRAM when initializing the driver.
 
 endmenu # SPI Configuration
 

components/driver/include/driver/spi_common.h

@@ -87,6 +87,11 @@ typedef struct {
     int quadhd_io_num;              ///< GPIO pin for HD (HolD) signal which is used as D3 in 4-bit communication modes, or -1 if not used.
     int max_transfer_sz;            ///< Maximum transfer size, in bytes. Defaults to 4094 if 0.
     uint32_t flags;                 ///< Abilities of bus to be checked by the driver. Or-ed value of ``SPICOMMON_BUSFLAG_*`` flags.
+    int intr_flags;    /**< Interrupt flag for the bus to set the priority, and IRAM attribute, see
+                         *  ``esp_intr_alloc.h``. Note that the EDGE, INTRDISABLED attribute are ignored
+                         *  by the driver. Note that if ESP_INTR_FLAG_IRAM is set, ALL the callbacks of
+                         *  the driver, and their callee functions, should be put in the IRAM.
+                         */
 } spi_bus_config_t;
 
 

components/driver/include/driver/spi_master.h

@@ -79,8 +79,26 @@ typedef struct {
     int spics_io_num;               ///< CS GPIO pin for this device, or -1 if not used
     uint32_t flags;                 ///< Bitwise OR of SPI_DEVICE_* flags
     int queue_size;                 ///< Transaction queue size. This sets how many transactions can be 'in the air' (queued using spi_device_queue_trans but not yet finished using spi_device_get_trans_result) at the same time
-    transaction_cb_t pre_cb;        ///< Callback to be called before a transmission is started. This callback is called within interrupt context.
+    transaction_cb_t pre_cb;   /**< Callback to be called before a transmission is started.
-    transaction_cb_t post_cb;       ///< Callback to be called after a transmission has completed. This callback is called within interrupt context.
+                                 *
+                                 *  This callback is called within interrupt
+                                 *  context should be in IRAM for best
+                                 *  performance, see "Transferring Speed"
+                                 *  section in the SPI Master documentation for
+                                 *  full details. If not, the callback may crash
+                                 *  during flash operation when the driver is
+                                 *  initialized with ESP_INTR_FLAG_IRAM.
+                                 */
+    transaction_cb_t post_cb;  /**< Callback to be called after a transmission has completed.
+                                 *
+                                 *  This callback is called within interrupt
+                                 *  context should be in IRAM for best
+                                 *  performance, see "Transferring Speed"
+                                 *  section in the SPI Master documentation for
+                                 *  full details. If not, the callback may crash
+                                 *  during flash operation when the driver is
+                                 *  initialized with ESP_INTR_FLAG_IRAM.
+                                 */
 } spi_device_interface_config_t;
 
 

components/driver/include/driver/spi_slave.h

@@ -44,8 +44,26 @@ typedef struct {
     uint32_t flags;                 ///< Bitwise OR of SPI_SLAVE_* flags
     int queue_size;                 ///< Transaction queue size. This sets how many transactions can be 'in the air' (queued using spi_slave_queue_trans but not yet finished using spi_slave_get_trans_result) at the same time
     uint8_t mode;                   ///< SPI mode (0-3)
-    slave_transaction_cb_t post_setup_cb; ///< Callback called after the SPI registers are loaded with new data
+    slave_transaction_cb_t post_setup_cb;  /**< Callback called after the SPI registers are loaded with new data.
-    slave_transaction_cb_t post_trans_cb; ///< Callback called after a transaction is done
+                                             *
+                                             *  This callback is called within interrupt
+                                             *  context should be in IRAM for best
+                                             *  performance, see "Transferring Speed"
+                                             *  section in the SPI Master documentation for
+                                             *  full details. If not, the callback may crash
+                                             *  during flash operation when the driver is
+                                             *  initialized with ESP_INTR_FLAG_IRAM.
+                                             */
+    slave_transaction_cb_t post_trans_cb;  /**< Callback called after a transaction is done.
+                                             *
+                                             *  This callback is called within interrupt
+                                             *  context should be in IRAM for best
+                                             *  performance, see "Transferring Speed"
+                                             *  section in the SPI Master documentation for
+                                             *  full details. If not, the callback may crash
+                                             *  during flash operation when the driver is
+                                             *  initialized with ESP_INTR_FLAG_IRAM.
+                                             */
 } spi_slave_interface_config_t;
 
 /**

components/driver/spi_master.c

@@ -233,6 +233,10 @@ esp_err_t spi_bus_initialize(spi_host_device_t host, const spi_bus_config_t *bus
 
     SPI_CHECK(host>=SPI_HOST && host<=VSPI_HOST, "invalid host", ESP_ERR_INVALID_ARG);
     SPI_CHECK( dma_chan >= 0 && dma_chan <= 2, "invalid dma channel", ESP_ERR_INVALID_ARG );
+    SPI_CHECK((bus_config->intr_flags & (ESP_INTR_FLAG_HIGH|ESP_INTR_FLAG_EDGE|ESP_INTR_FLAG_INTRDISABLED))==0, "intr flag not allowed", ESP_ERR_INVALID_ARG);
+#ifndef CONFIG_SPI_MASTER_ISR_IN_IRAM
+    SPI_CHECK((bus_config->intr_flags & ESP_INTR_FLAG_IRAM)==0, "ESP_INTR_FLAG_IRAM should be disabled when CONFIG_SPI_MASTER_ISR_IN_IRAM is not set.", ESP_ERR_INVALID_ARG);
+#endif
 
     spi_chan_claimed=spicommon_periph_claim(host, "spi master");
     SPI_CHECK(spi_chan_claimed, "host already in use", ESP_ERR_INVALID_STATE);
@@ -284,10 +288,7 @@ esp_err_t spi_bus_initialize(spi_host_device_t host, const spi_bus_config_t *bus
         }
     }
 
-    int flags = ESP_INTR_FLAG_INTRDISABLED;
+    int flags = bus_config->intr_flags | ESP_INTR_FLAG_INTRDISABLED;
-#ifdef CONFIG_SPI_MASTER_ISR_IN_IRAM
-    flags |= ESP_INTR_FLAG_IRAM;
-#endif
     err = esp_intr_alloc(spicommon_irqsource_for_host(host), flags, spi_intr, (void*)spihost[host], &spihost[host]->intr);
     if (err != ESP_OK) {
         ret = err;

components/driver/spi_slave.c

@@ -109,6 +109,10 @@ esp_err_t spi_slave_initialize(spi_host_device_t host, const spi_bus_config_t *b
     //We only support HSPI/VSPI, period.
     SPI_CHECK(VALID_HOST(host), "invalid host", ESP_ERR_INVALID_ARG);
     SPI_CHECK( dma_chan >= 0 && dma_chan <= 2, "invalid dma channel", ESP_ERR_INVALID_ARG );
+    SPI_CHECK((bus_config->intr_flags & (ESP_INTR_FLAG_HIGH|ESP_INTR_FLAG_EDGE|ESP_INTR_FLAG_INTRDISABLED))==0, "intr flag not allowed", ESP_ERR_INVALID_ARG);
+#ifndef CONFIG_SPI_SLAVE_ISR_IN_IRAM
+    SPI_CHECK((bus_config->intr_flags & ESP_INTR_FLAG_IRAM)==0, "ESP_INTR_FLAG_IRAM should be disabled when CONFIG_SPI_SLAVE_ISR_IN_IRAM is not set.", ESP_ERR_INVALID_ARG);
+#endif
 
     spi_chan_claimed=spicommon_periph_claim(host, "spi slave");
     SPI_CHECK(spi_chan_claimed, "host already in use", ESP_ERR_INVALID_STATE);
@@ -174,10 +178,7 @@ esp_err_t spi_slave_initialize(spi_host_device_t host, const spi_bus_config_t *b
         goto cleanup;
     }
 
-    int flags = ESP_INTR_FLAG_INTRDISABLED;
+    int flags = bus_config->intr_flags | ESP_INTR_FLAG_INTRDISABLED;
-#ifdef CONFIG_SPI_SLAVE_ISR_IN_IRAM
-    flags |= ESP_INTR_FLAG_IRAM;
-#endif
     err = esp_intr_alloc(spicommon_irqsource_for_host(host), flags, spi_intr, (void *)spihost[host], &spihost[host]->intr);
     if (err != ESP_OK) {
         ret = err;

docs/en/api-reference/peripherals/spi_master.rst

@@ -305,7 +305,8 @@ Speed and Timing Considerations
 Transferring speed
 ^^^^^^^^^^^^^^^^^^
 
-There're two factors limiting the transferring speed: (1) The transaction interval, (2) The SPI clock frequency used.
+There're three factors limiting the transferring speed: (1) The transaction interval, (2) The SPI clock frequency used.
+(3) The cache miss of SPI functions including callbacks.
 When large transactions are used, the clock frequency determines the transferring speed; while the interval effects the
 speed a lot if small transactions are used.
 
@@ -343,6 +344,13 @@ speed a lot if small transactions are used.
     2. SPI clock frequency: Each byte transferred takes 8 times of the clock period *8/fspi*. If the clock frequency is
        too high, some functions may be limited to use. See :ref:`timing_considerations`.
 
+    3. The cache miss: the default config puts only the ISR into the IRAM.
+       Other SPI related functions including the driver itself and the callback
+       may suffer from the cache miss and wait for some time while reading code
+       from the flash. Select :ref:`CONFIG_SPI_MASTER_IN_IRAM` to put the whole
+       SPI driver into IRAM, and put the entire callback(s) and its callee
+       functions into IRAM to prevent this.
+
 For an interrupt transaction, the overall cost is *20+8n/Fspi[MHz]* [us] for n bytes tranferred
 in one transaction. Hence the transferring speed is : *n/(20+8n/Fspi)*. Example of transferring speed under 8MHz
 clock speed:
@@ -366,6 +374,15 @@ clock speed:
 When the length of transaction is short, the cost of transaction interval is really high. Please try to squash data
 into one transaction if possible to get higher transfer speed.
 
+BTW, the ISR is disabled during flash operation by default. To keep sending
+transactions during flash operations, enable
+:ref:`CONFIG_SPI_MASTER_ISR_IN_IRAM` and set :cpp:class:`ESP_INTR_FLAG_IRAM`
+in the ``intr_flags`` member of :cpp:class:`spi_bus_config_t`. Then all the
+transactions queued before the flash operations will be handled by the ISR
+continuously during flash operation. Note that the callback of each devices,
+and their callee functions, should be in the IRAM in this case, or your
+callback will crash due to cache miss.
+
 .. _timing_considerations:
 
 Timing considerations