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[5/8] spi: rspi: Increase bit rate range for RSPI on SH

Message ID 20200608095940.30516-6-geert+renesas@glider.be
State Accepted
Commit 4e71d926abbe9ec23415f2ec8685a7bc26c1ceed
Headers show
Series spi: rspi: Bit rate improvements | expand

Commit Message

Geert Uytterhoeven June 8, 2020, 9:59 a.m. UTC 
Increase bit rate range for RSPI on legacy SH by making use of the Bit
Rate Frequency Division Setting field in Command Registers, just like is
already done on RZ/A.  This decreases the lower limit by a factor of 8.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Untested due to lack of hardware, but the formulas in the datasheets for
SH7753, RZ/A1H, and RZ/A2M are the same.
---
 drivers/spi/spi-rspi.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)
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Patch

diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
index ad4ac867170b101a..ea3f2680d3c13e02 100644
--- a/drivers/spi/spi-rspi.c
+++ b/drivers/spi/spi-rspi.c
@@ -248,19 +248,32 @@  struct spi_ops {
 	u8 num_hw_ss;
 };
 
+static void rspi_set_rate(struct rspi_data *rspi)
+{
+	unsigned long clksrc;
+	int brdv = 0, spbr;
+
+	clksrc = clk_get_rate(rspi->clk);
+	spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1;
+	while (spbr > 255 && brdv < 3) {
+		brdv++;
+		spbr = DIV_ROUND_UP(spbr + 1, 2) - 1;
+	}
+
+	rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
+	rspi->spcmd |= SPCMD_BRDV(brdv);
+}
+
 /*
  * functions for RSPI on legacy SH
  */
 static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
 {
-	int spbr;
-
 	/* Sets output mode, MOSI signal, and (optionally) loopback */
 	rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
 
 	/* Sets transfer bit rate */
-	spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz) - 1;
-	rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
+	rspi_set_rate(rspi);
 
 	/* Disable dummy transmission, set 16-bit word access, 1 frame */
 	rspi_write8(rspi, 0, RSPI_SPDCR);
@@ -290,23 +303,11 @@  static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
  */
 static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size)
 {
-	int spbr;
-	int brdv = 0;
-	unsigned long clksrc;
-
 	/* Sets output mode, MOSI signal, and (optionally) loopback */
 	rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
 
-	clksrc = clk_get_rate(rspi->clk);
-	spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1;
-	while (spbr > 255 && brdv < 3) {
-		brdv++;
-		spbr = DIV_ROUND_UP(spbr + 1, 2) - 1;
-	}
-
 	/* Sets transfer bit rate */
-	rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
-	rspi->spcmd |= SPCMD_BRDV(brdv);
+	rspi_set_rate(rspi);
 
 	/* Disable dummy transmission, set byte access */
 	rspi_write8(rspi, SPDCR_SPLBYTE, RSPI_SPDCR);