[PATCH 3/3] mtd: spinand: winbond: Clarify when to enable the HS bit

[Miquel Raynal]

Above 104MHz when in fast dual or quad I/O reads, the delay between
address and data cycles is too short. It is possible to reach higher
frequencies, up to 166MHz, by adding a few more dummy cycles through the
setting of the HS bit. Improve the condition for enabling this bit, and
also make sure we set it at soon as we go over 104MHz.

Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
This is a port from Linux.
---
 drivers/mtd/nand/spi/winbond.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/spi/winbond.c b/drivers/mtd/nand/spi/winbond.c
index 79c3354efb65..accb46dfeb03 100644
--- a/drivers/mtd/nand/spi/winbond.c
+++ b/drivers/mtd/nand/spi/winbond.c
@@ -261,16 +261,19 @@ static int w25n0xjw_hs_cfg(struct spinand_device *spinand)
 	u8 sr4;
 	int ret;
 
+	/*
+	 * SDR dual and quad I/O operations over 104MHz require the HS bit to
+	 * enable a few more dummy cycles.
+	 */
 	op = spinand->op_templates.read_cache;
 	if (op->cmd.dtr || op->addr.dtr || op->dummy.dtr || op->data.dtr)
 		hs = false;
-	else if (op->cmd.buswidth == 1 && op->addr.buswidth == 1 &&
-		 op->dummy.buswidth == 1 && op->data.buswidth == 1)
+	else if (op->cmd.buswidth != 1 || op->addr.buswidth != 1)
+		hs = false;
+	else if (op->max_freq && op->max_freq <= 104 * HZ_PER_MHZ)
 		hs = false;
-	else if (!op->max_freq)
-		hs = true;
 	else
-		hs = false;
+		hs = true;
 
 	ret = spinand_read_reg_op(spinand, W25N0XJW_SR4, &sr4);
 	if (ret)

-- 
2.53.0