[U-Boot] [PATCH v2 3/3] spi: cadence_qspi_apb: Make flash writes 32 bit aligned

[Vignesh R]

Make flash writes 32 bit aligned by using bounce buffers to deal with
non 32 bit aligned buffers.
This is required because as per TI K2G TRM[1], the external master is
only permitted to issue 32-bit data interface writes until the last word
of an indirect transfer. Otherwise indirect writes is known to fail
sometimes.

[1] http://www.ti.com/lit/ug/spruhy8g/spruhy8g.pdf

Signed-off-by: Vignesh R <vigneshr at ti.com>
---

v2: Move bounce buffer within cadence_qspi_apb_indirect_write_execute()
    to handle arbitrary length buffers.


 drivers/spi/cadence_qspi_apb.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c
index fa8af33ae19b..23441964a543 100644
--- a/drivers/spi/cadence_qspi_apb.c
+++ b/drivers/spi/cadence_qspi_apb.c
@@ -30,6 +30,7 @@
 #include <linux/errno.h>
 #include <wait_bit.h>
 #include <spi.h>
+#include <malloc.h>
 #include "cadence_qspi.h"
 
 #define CQSPI_REG_POLL_US			1 /* 1us */
@@ -715,9 +716,23 @@ int cadence_qspi_apb_indirect_write_execute(struct cadence_spi_platdata *plat,
 {
 	unsigned int page_size = plat->page_size;
 	unsigned int remaining = n_tx;
+	const u8 *bb_txbuf = txbuf;
+	void *bounce_buf = NULL;
 	unsigned int write_bytes;
 	int ret;
 
+	/*
+	 * Use bounce buffer for non 32 bit aligned txbuf to avoid data
+	 * aborts
+	 */
+	if ((uintptr_t)txbuf % 4) {
+		bounce_buf = malloc(n_tx);
+		if (!bounce_buf)
+			return -ENOMEM;
+		memcpy(bounce_buf, txbuf, n_tx);
+		bb_txbuf = bounce_buf;
+	}
+
 	/* Configure the indirect read transfer bytes */
 	writel(n_tx, plat->regbase + CQSPI_REG_INDIRECTWRBYTES);
 
@@ -727,11 +742,11 @@ int cadence_qspi_apb_indirect_write_execute(struct cadence_spi_platdata *plat,
 
 	while (remaining > 0) {
 		write_bytes = remaining > page_size ? page_size : remaining;
-		/* Handle non-4-byte aligned access to avoid data abort. */
-		if (((uintptr_t)txbuf % 4) || (write_bytes % 4))
-			writesb(plat->ahbbase, txbuf, write_bytes);
-		else
-			writesl(plat->ahbbase, txbuf, write_bytes >> 2);
+		writesl(plat->ahbbase, bb_txbuf, write_bytes >> 2);
+		if (write_bytes % 4)
+			writesb(plat->ahbbase,
+				bb_txbuf + rounddown(write_bytes, 4),
+				write_bytes % 4);
 
 		ret = wait_for_bit("QSPI", plat->regbase + CQSPI_REG_SDRAMLEVEL,
 				   CQSPI_REG_SDRAMLEVEL_WR_MASK <<
@@ -741,7 +756,7 @@ int cadence_qspi_apb_indirect_write_execute(struct cadence_spi_platdata *plat,
 			goto failwr;
 		}
 
-		txbuf += write_bytes;
+		bb_txbuf += write_bytes;
 		remaining -= write_bytes;
 	}
 
@@ -756,12 +771,16 @@ int cadence_qspi_apb_indirect_write_execute(struct cadence_spi_platdata *plat,
 	/* Clear indirect completion status */
 	writel(CQSPI_REG_INDIRECTWR_DONE,
 	       plat->regbase + CQSPI_REG_INDIRECTWR);
+	if (bounce_buf)
+		free(bounce_buf);
 	return 0;
 
 failwr:
 	/* Cancel the indirect write */
 	writel(CQSPI_REG_INDIRECTWR_CANCEL,
 	       plat->regbase + CQSPI_REG_INDIRECTWR);
+	if (bounce_buf)
+		free(bounce_buf);
 	return ret;
 }
 
-- 
2.15.1