can: mcp251xfd: add support for internal PLL

The PLL is enabled if the configured clock is less than or equal to 10 times
the max clock frequency.

The device will operate with two different SPI speeds. A slow speed determined
by the clock without the PLL enabled, and a fast speed derived from the
frequency with the PLL enabled.

Link: https://lore.kernel.org/all/20220207131047.282110-16-mkl@pengutronix.de
Link: https://lore.kernel.org/all/20201015124401.2766-3-mas@csselectronics.comCo-developed-by: Magnus Aagaard Sørensen <mas@csselectronics.com>
Signed-off-by: Magnus Aagaard Sørensen <mas@csselectronics.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c

@@ -326,8 +326,13 @@ static int mcp251xfd_chip_wake(const struct mcp251xfd_priv *priv)
 	 */
 	osc = FIELD_PREP(MCP251XFD_REG_OSC_CLKODIV_MASK,
 			 MCP251XFD_REG_OSC_CLKODIV_10);
+
+	/* We cannot check for the PLL ready bit (either set or
+	 * unset), as the PLL might be enabled. This can happen if the
+	 * system reboots, while the mcp251xfd stays powered.
+	 */
 	osc_reference = MCP251XFD_REG_OSC_OSCRDY;
-	osc_mask = MCP251XFD_REG_OSC_OSCRDY | MCP251XFD_REG_OSC_PLLRDY;
+	osc_mask = MCP251XFD_REG_OSC_OSCRDY;
 
 	/* If the controller is in Sleep Mode the following write only
 	 * removes the "Oscillator Disable" bit and powers it up. All
@@ -346,6 +351,21 @@ static int mcp251xfd_chip_wake(const struct mcp251xfd_priv *priv)
 
 static inline int mcp251xfd_chip_sleep(const struct mcp251xfd_priv *priv)
 {
+	if (priv->pll_enable) {
+		u32 osc;
+		int err;
+
+		/* Turn off PLL */
+		osc = FIELD_PREP(MCP251XFD_REG_OSC_CLKODIV_MASK,
+				 MCP251XFD_REG_OSC_CLKODIV_10);
+		err = regmap_write(priv->map_reg, MCP251XFD_REG_OSC, osc);
+		if (err)
+			netdev_err(priv->ndev,
+				   "Failed to disable PLL.\n");
+
+		priv->spi->max_speed_hz = priv->spi_max_speed_hz_slow;
+	}
+
 	return mcp251xfd_chip_set_mode(priv, MCP251XFD_REG_CON_MODE_SLEEP);
 }
 
@@ -442,6 +462,11 @@ static int mcp251xfd_chip_clock_init(const struct mcp251xfd_priv *priv)
 	osc_reference = MCP251XFD_REG_OSC_OSCRDY;
 	osc_mask = MCP251XFD_REG_OSC_OSCRDY | MCP251XFD_REG_OSC_PLLRDY;
 
+	if (priv->pll_enable) {
+		osc |= MCP251XFD_REG_OSC_PLLEN;
+		osc_reference |= MCP251XFD_REG_OSC_PLLRDY;
+	}
+
 	err = regmap_write(priv->map_reg, MCP251XFD_REG_OSC, osc);
 	if (err)
 		return err;
@@ -450,6 +475,8 @@ static int mcp251xfd_chip_clock_init(const struct mcp251xfd_priv *priv)
 	if (err)
 		return err;
 
+	priv->spi->max_speed_hz = priv->spi_max_speed_hz_fast;
+
 	return 0;
 }
 
@@ -1692,8 +1719,9 @@ static int mcp251xfd_register_check_rx_int(struct mcp251xfd_priv *priv)
 }
 
 static int
-mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv,
-			      u32 *dev_id, u32 *effective_speed_hz)
+mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv, u32 *dev_id,
+			      u32 *effective_speed_hz_slow,
+			      u32 *effective_speed_hz_fast)
 {
 	struct mcp251xfd_map_buf_nocrc *buf_rx;
 	struct mcp251xfd_map_buf_nocrc *buf_tx;
@@ -1712,16 +1740,20 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv,
 
 	xfer[0].tx_buf = buf_tx;
 	xfer[0].len = sizeof(buf_tx->cmd);
+	xfer[0].speed_hz = priv->spi_max_speed_hz_slow;
 	xfer[1].rx_buf = buf_rx->data;
 	xfer[1].len = sizeof(dev_id);
+	xfer[1].speed_hz = priv->spi_max_speed_hz_fast;
 
 	mcp251xfd_spi_cmd_read_nocrc(&buf_tx->cmd, MCP251XFD_REG_DEVID);
+
 	err = spi_sync_transfer(priv->spi, xfer, ARRAY_SIZE(xfer));
 	if (err)
 		goto out_kfree_buf_tx;
 
 	*dev_id = be32_to_cpup((__be32 *)buf_rx->data);
-	*effective_speed_hz = xfer->effective_speed_hz;
+	*effective_speed_hz_slow = xfer[0].effective_speed_hz;
+	*effective_speed_hz_fast = xfer[1].effective_speed_hz;
 
  out_kfree_buf_tx:
 	kfree(buf_tx);
@@ -1737,34 +1769,45 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv,
 static int
 mcp251xfd_register_done(const struct mcp251xfd_priv *priv)
 {
-	u32 dev_id, effective_speed_hz;
+	u32 dev_id, effective_speed_hz_slow, effective_speed_hz_fast;
+	unsigned long clk_rate;
 	int err;
 
 	err = mcp251xfd_register_get_dev_id(priv, &dev_id,
-					    &effective_speed_hz);
+					    &effective_speed_hz_slow,
+					    &effective_speed_hz_fast);
 	if (err)
 		return err;
 
+	clk_rate = clk_get_rate(priv->clk);
+
 	netdev_info(priv->ndev,
-		    "%s rev%lu.%lu (%cRX_INT %cMAB_NO_WARN %cCRC_REG %cCRC_RX %cCRC_TX %cECC %cHD c:%u.%02uMHz m:%u.%02uMHz r:%u.%02uMHz e:%u.%02uMHz) successfully initialized.\n",
+		    "%s rev%lu.%lu (%cRX_INT %cPLL %cMAB_NO_WARN %cCRC_REG %cCRC_RX %cCRC_TX %cECC %cHD o:%lu.%02luMHz c:%u.%02uMHz m:%u.%02uMHz rs:%u.%02uMHz es:%u.%02uMHz rf:%u.%02uMHz ef:%u.%02uMHz) successfully initialized.\n",
 		    mcp251xfd_get_model_str(priv),
 		    FIELD_GET(MCP251XFD_REG_DEVID_ID_MASK, dev_id),
 		    FIELD_GET(MCP251XFD_REG_DEVID_REV_MASK, dev_id),
 		    priv->rx_int ? '+' : '-',
+		    priv->pll_enable ? '+' : '-',
 		    MCP251XFD_QUIRK_ACTIVE(MAB_NO_WARN),
 		    MCP251XFD_QUIRK_ACTIVE(CRC_REG),
 		    MCP251XFD_QUIRK_ACTIVE(CRC_RX),
 		    MCP251XFD_QUIRK_ACTIVE(CRC_TX),
 		    MCP251XFD_QUIRK_ACTIVE(ECC),
 		    MCP251XFD_QUIRK_ACTIVE(HALF_DUPLEX),
+		    clk_rate / 1000000,
+		    clk_rate % 1000000 / 1000 / 10,
 		    priv->can.clock.freq / 1000000,
 		    priv->can.clock.freq % 1000000 / 1000 / 10,
 		    priv->spi_max_speed_hz_orig / 1000000,
 		    priv->spi_max_speed_hz_orig % 1000000 / 1000 / 10,
-		    priv->spi->max_speed_hz / 1000000,
-		    priv->spi->max_speed_hz % 1000000 / 1000 / 10,
-		    effective_speed_hz / 1000000,
-		    effective_speed_hz % 1000000 / 1000 / 10);
+		    priv->spi_max_speed_hz_slow / 1000000,
+		    priv->spi_max_speed_hz_slow % 1000000 / 1000 / 10,
+		    effective_speed_hz_slow / 1000000,
+		    effective_speed_hz_slow % 1000000 / 1000 / 10,
+		    priv->spi_max_speed_hz_fast / 1000000,
+		    priv->spi_max_speed_hz_fast % 1000000 / 1000 / 10,
+		    effective_speed_hz_fast / 1000000,
+		    effective_speed_hz_fast % 1000000 / 1000 / 10);
 
 	return 0;
 }
@@ -1891,6 +1934,7 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	struct gpio_desc *rx_int;
 	struct regulator *reg_vdd, *reg_xceiver;
 	struct clk *clk;
+	bool pll_enable = false;
 	u32 freq = 0;
 	int err;
 
@@ -1941,12 +1985,8 @@ static int mcp251xfd_probe(struct spi_device *spi)
 		return -ERANGE;
 	}
 
-	if (freq <= MCP251XFD_SYSCLOCK_HZ_MAX / MCP251XFD_OSC_PLL_MULTIPLIER) {
-		dev_err(&spi->dev,
-			"Oscillator frequency (%u Hz) is too low and PLL is not supported.\n",
-			freq);
-		return -ERANGE;
-	}
+	if (freq <= MCP251XFD_SYSCLOCK_HZ_MAX / MCP251XFD_OSC_PLL_MULTIPLIER)
+		pll_enable = true;
 
 	ndev = alloc_candev(sizeof(struct mcp251xfd_priv),
 			    MCP251XFD_TX_OBJ_NUM_MAX);
@@ -1962,6 +2002,8 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	priv = netdev_priv(ndev);
 	spi_set_drvdata(spi, priv);
 	priv->can.clock.freq = freq;
+	if (pll_enable)
+		priv->can.clock.freq *= MCP251XFD_OSC_PLL_MULTIPLIER;
 	priv->can.do_set_mode = mcp251xfd_set_mode;
 	priv->can.do_get_berr_counter = mcp251xfd_get_berr_counter;
 	priv->can.bittiming_const = &mcp251xfd_bittiming_const;
@@ -1974,6 +2016,7 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	priv->spi = spi;
 	priv->rx_int = rx_int;
 	priv->clk = clk;
+	priv->pll_enable = pll_enable;
 	priv->reg_vdd = reg_vdd;
 	priv->reg_xceiver = reg_xceiver;
 
@@ -2011,7 +2054,16 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	 *
 	 */
 	priv->spi_max_speed_hz_orig = spi->max_speed_hz;
-	spi->max_speed_hz = min(spi->max_speed_hz, freq / 2 / 1000 * 850);
+	priv->spi_max_speed_hz_slow = min(spi->max_speed_hz,
+					  freq / 2 / 1000 * 850);
+	if (priv->pll_enable)
+		priv->spi_max_speed_hz_fast = min(spi->max_speed_hz,
+						  freq *
+						  MCP251XFD_OSC_PLL_MULTIPLIER /
+						  2 / 1000 * 850);
+	else
+		priv->spi_max_speed_hz_fast = priv->spi_max_speed_hz_slow;
+	spi->max_speed_hz = priv->spi_max_speed_hz_slow;
 	spi->bits_per_word = 8;
 	spi->rt = true;
 	err = spi_setup(spi);

drivers/net/can/spi/mcp251xfd/mcp251xfd.h

@@ -2,8 +2,8 @@
  *
  * mcp251xfd - Microchip MCP251xFD Family CAN controller driver
  *
- * Copyright (c) 2019 Pengutronix,
- *                    Marc Kleine-Budde <kernel@pengutronix.de>
+ * Copyright (c) 2019, 2020 Pengutronix,
+ *               Marc Kleine-Budde <kernel@pengutronix.de>
  * Copyright (c) 2019 Martin Sperl <kernel@martin.sperl.org>
  */
 
@@ -592,6 +592,8 @@ struct mcp251xfd_priv {
 
 	struct spi_device *spi;
 	u32 spi_max_speed_hz_orig;
+	u32 spi_max_speed_hz_fast;
+	u32 spi_max_speed_hz_slow;
 
 	struct mcp251xfd_tef_ring tef[1];
 	struct mcp251xfd_tx_ring tx[1];
@@ -608,6 +610,7 @@ struct mcp251xfd_priv {
 
 	struct gpio_desc *rx_int;
 	struct clk *clk;
+	bool pll_enable;
 	struct regulator *reg_vdd;
 	struct regulator *reg_xceiver;