drivers: memc: memc_mcux_flexspi: allow setting ahb alignment boundary

Some instances of the FLEXSPI IP permit limiting AHB bus access so that
no memory access requests will straddle a page boundary. Add a property
to manage this setting.

Signed-off-by: Daniel DeGrasse <[email protected]>

Author: danieldegrasse

drivers/memc/memc_mcux_flexspi.c

@@ -53,6 +53,7 @@ struct memc_flexspi_data {
 	bool ahb_cacheable;
 	bool ahb_prefetch;
 	bool ahb_read_addr_opt;
+	uint8_t ahb_boundary;
 	bool combination_mode;
 	bool sck_differential_clock;
 	flexspi_read_sample_clock_t rx_sample_clock;
@@ -342,6 +343,12 @@ FSL_FEATURE_FLEXSPI_SUPPORT_SEPERATE_RXCLKSRC_PORTB
 
 	FLEXSPI_Init(data->base, &flexspi_config);
 
+#if defined(FLEXSPI_AHBCR_ALIGNMENT_MASK)
+	/* Configure AHB alignment boundary */
+	data->base->AHBCR = (data->base->AHBCR & ~FLEXSPI_AHBCR_ALIGNMENT_MASK) |
+		FLEXSPI_AHBCR_ALIGNMENT(data->ahb_boundary);
+#endif
+
 	if (memc_flexspi_is_running_xip(dev)) {
 		/* Restore flash sizes */
 		for (i = 0; i < kFLEXSPI_PortCount; i++) {
@@ -414,6 +421,7 @@ static int memc_flexspi_pm_action(const struct device *dev, enum pm_device_actio
 		.ahb_cacheable = DT_INST_PROP(n, ahb_cacheable),	\
 		.ahb_prefetch = DT_INST_PROP(n, ahb_prefetch),		\
 		.ahb_read_addr_opt = DT_INST_PROP(n, ahb_read_addr_opt),\
+		.ahb_boundary = DT_INST_ENUM_IDX(n, ahb_boundary),	\
 		.combination_mode = DT_INST_PROP(n, combination_mode),	\
 		.sck_differential_clock = DT_INST_PROP(n, sck_differential_clock),	\
 		.rx_sample_clock = DT_INST_PROP(n, rx_clock_source),	\

dts/bindings/spi/nxp,imx-flexspi.yaml

@@ -86,6 +86,18 @@ properties:
       master_id: AHBRXBUFxCRx[MSTRID]
       buf_size: AHBRXBUFxCRx[BUFSZ]
 
+  ahb-boundary:
+    type: string
+    default: "no-boundary"
+    enum:
+      - "no-boundary"
+      - "1024"
+      - "512"
+      - "256"
+    description: |
+      Sets the AHB read/write boundary. Only supported by some versions of
+      the FLEXSPI IP. When set, all memory accesses that cross an address
+      boundary of the specified size will be divided into smaller sub accesses.
 
 child-binding:
   description: NXP FlexSPI port