[Patch v2 1/2] spi: nxp-fspi: Add support for IP read only

[Kuldeep Singh]

Add support for disabling AHB bus and read entire flash contents via IP
bus only. Please note, this enables IP bus read using a quirk which can
be enabled directly in device-type data or in existence of an errata
where AHB bus may need to be disabled.

Signed-off-by: Kuldeep Singh <kuldeep.si...@nxp.com>
Acked-by: Jagan Teki <ja...@amarulasolutions.com>
---
v2:
- rebase to top of tree

 drivers/spi/nxp_fspi.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/nxp_fspi.c b/drivers/spi/nxp_fspi.c
index 6c5bad4c2c..e1b3d2d77b 100644
--- a/drivers/spi/nxp_fspi.c
+++ b/drivers/spi/nxp_fspi.c
@@ -304,6 +304,9 @@
 #define POLL_TOUT              5000
 #define NXP_FSPI_MAX_CHIPSELECT                4
 
+/* Access flash memory using IP bus only */
+#define FSPI_QUIRK_USE_IP_ONLY         BIT(0)
+
 struct nxp_fspi_devtype_data {
        unsigned int rxfifo;
        unsigned int txfifo;
@@ -338,6 +341,11 @@ struct nxp_fspi {
        const struct nxp_fspi_devtype_data *devtype_data;
 };
 
+static inline int needs_ip_only(struct nxp_fspi *f)
+{
+       return f->devtype_data->quirks & FSPI_QUIRK_USE_IP_ONLY;
+}
+
 /*
  * R/W functions for big- or little-endian registers:
  * The FSPI controller's endianness is independent of
@@ -769,12 +777,14 @@ static int nxp_fspi_exec_op(struct spi_slave *slave,
 
        nxp_fspi_prepare_lut(f, op);
        /*
-        * If we have large chunks of data, we read them through the AHB bus
-        * by accessing the mapped memory. In all other cases we use
-        * IP commands to access the flash.
+        * If we have large chunks of data, we read them through the AHB bus by
+        * accessing the mapped memory. In all other cases we use IP commands
+        * to access the flash. Read via AHB bus may be corrupted due to
+        * existence of an errata and therefore discard AHB read in such cases.
         */
        if (op->data.nbytes > (f->devtype_data->rxfifo - 4) &&
-           op->data.dir == SPI_MEM_DATA_IN) {
+           op->data.dir == SPI_MEM_DATA_IN &&
+           !needs_ip_only(f)) {
                nxp_fspi_read_ahb(f, op);
        } else {
                if (op->data.nbytes && op->data.dir == SPI_MEM_DATA_OUT)
@@ -808,6 +818,12 @@ static int nxp_fspi_adjust_op_size(struct spi_slave *slave,
                        op->data.nbytes = ALIGN_DOWN(op->data.nbytes, 8);
        }
 
+       /* Limit data bytes to RX FIFO in case of IP read only */
+       if (needs_ip_only(f) &&
+           op->data.dir == SPI_MEM_DATA_IN &&
+           op->data.nbytes > f->devtype_data->rxfifo)
+               op->data.nbytes = f->devtype_data->rxfifo;
+
        return 0;
 }
 
-- 
2.25.1