[PATCH v3 3/5] serial: 8250_exar: Replace custom EEPROM read with eeprom_93cx6

[Parker Newman <parker@finest.io>]

From: Parker Newman <pnewman@connecttech.com>

Replace the custom 93cx6 EEPROM read functions with the eeprom_93cx6
driver. This removes duplicate code and improves code readability.

Replace exar_ee_read() calls with eeprom_93cx6_read() or
eeprom_93cx6_multiread().

Add "select EEPROM_93CX6" to config SERIAL_8250_EXAR to ensure
eeprom_93cx6 driver is also compiled when 8250_exar driver is selected.

Note: Old exar_ee_read() and associated functions are removed in next
patch in this series.

Link to mailing list discussion with Andy Shevchenko for reference.

Link: https://lore.kernel.org/linux-serial/Ztr5u2wEt8VF1IdI@black.fi.intel.com/
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Parker Newman <pnewman@connecttech.com>
---
Changes in v2:
- Refactored cti_read_osc_freq() based on feedback.
- Moved Kconfig change into this patch.
- Sorted headers.
- Fixed comment.

Changes in v3:
- Commit message wording.
- Rebased to v6.12-rc1.

 drivers/tty/serial/8250/8250_exar.c | 55 +++++++++++++++++++++++------
 drivers/tty/serial/8250/Kconfig     |  1 +
 2 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index b7a75db15249..c40e86920110 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -11,6 +11,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/dmi.h>
+#include <linux/eeprom_93cx6.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/math.h>
@@ -252,6 +253,7 @@ struct exar8250 {
 	unsigned int		nr;
 	unsigned int		osc_freq;
 	struct exar8250_board	*board;
+	struct eeprom_93cx6	eeprom;
 	void __iomem		*virt;
 	int			line[];
 };
@@ -355,6 +357,39 @@ static u16 exar_ee_read(struct exar8250 *priv, u8 ee_addr)
 	return data;
 }

+static void exar_eeprom_93cx6_reg_read(struct eeprom_93cx6 *eeprom)
+{
+	struct exar8250 *priv = eeprom->data;
+	u8 regb = exar_read_reg(priv, UART_EXAR_REGB);
+
+	/* EECK and EECS always read 0 from REGB so only set EEDO */
+	eeprom->reg_data_out = regb & UART_EXAR_REGB_EEDO;
+}
+
+static void exar_eeprom_93cx6_reg_write(struct eeprom_93cx6 *eeprom)
+{
+	struct exar8250 *priv = eeprom->data;
+	u8 regb = 0;
+
+	if (eeprom->reg_data_in)
+		regb |= UART_EXAR_REGB_EEDI;
+	if (eeprom->reg_data_clock)
+		regb |= UART_EXAR_REGB_EECK;
+	if (eeprom->reg_chip_select)
+		regb |= UART_EXAR_REGB_EECS;
+
+	exar_write_reg(priv, UART_EXAR_REGB, regb);
+}
+
+static void exar_eeprom_init(struct exar8250 *priv)
+{
+	priv->eeprom.data = priv;
+	priv->eeprom.register_read = exar_eeprom_93cx6_reg_read;
+	priv->eeprom.register_write = exar_eeprom_93cx6_reg_write;
+	priv->eeprom.width = PCI_EEPROM_WIDTH_93C46;
+	priv->eeprom.quirks |= PCI_EEPROM_QUIRK_EXTRA_READ_CYCLE;
+}
+
 /**
  * exar_mpio_config_output() - Configure an Exar MPIO as an output
  * @priv: Device's private structure
@@ -696,20 +731,16 @@ static int cti_plx_int_enable(struct exar8250 *priv)
  */
 static int cti_read_osc_freq(struct exar8250 *priv, u8 eeprom_offset)
 {
-	u16 lower_word;
-	u16 upper_word;
+	__le16 ee_words[2];
+	u32 osc_freq;

-	lower_word = exar_ee_read(priv, eeprom_offset);
-	// Check if EEPROM word was blank
-	if (lower_word == 0xFFFF)
-		return -EIO;
+	eeprom_93cx6_multiread(&priv->eeprom, eeprom_offset, ee_words, ARRAY_SIZE(ee_words));

-	upper_word = exar_ee_read(priv, (eeprom_offset + 1));
-	if (upper_word == 0xFFFF)
+	osc_freq = le16_to_cpu(ee_words[0]) | (le16_to_cpu(ee_words[1]) << 16);
+	if (osc_freq == GENMASK(31, 0))
 		return -EIO;

-	return FIELD_PREP(CTI_EE_MASK_OSC_FREQ_LOWER, lower_word) |
-	       FIELD_PREP(CTI_EE_MASK_OSC_FREQ_UPPER, upper_word);
+	return osc_freq;
 }

 /**
@@ -833,7 +864,7 @@ static enum cti_port_type cti_get_port_type_xr17v35x(struct exar8250 *priv,
 	u8 offset;

 	offset = CTI_EE_OFF_XR17V35X_PORT_FLAGS + port_num;
-	port_flags = exar_ee_read(priv, offset);
+	eeprom_93cx6_read(&priv->eeprom, offset, &port_flags);

 	port_type = FIELD_GET(CTI_EE_MASK_PORT_FLAGS_TYPE, port_flags);
 	if (CTI_PORT_TYPE_VALID(port_type))
@@ -1551,6 +1582,8 @@ exar_pci_probe(struct pci_dev *pcidev, const struct pci_device_id *ent)
 	if (rc)
 		return rc;

+	exar_eeprom_init(priv);
+
 	for (i = 0; i < nr_ports && i < maxnr; i++) {
 		rc = board->setup(priv, pcidev, &uart, i);
 		if (rc) {
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 47ff50763c04..94910ced8238 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -150,6 +150,7 @@ config SERIAL_8250_EXAR
 	tristate "8250/16550 Exar/Commtech PCI/PCIe device support"
 	depends on SERIAL_8250 && PCI
 	select SERIAL_8250_PCILIB
+	select EEPROM_93CX6
 	default SERIAL_8250
 	help
 	  This builds support for XR17C1xx, XR17V3xx and some Commtech
--
2.46.0