[PATCH 5.11 20/36] misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom

gregkh
2021-03-10T13:25:48Z

From: Aswath Govindraju <a-govindraju@ti.com>

[ Upstream commit f6f1f8e6e3eea25f539105d48166e91f0ab46dd1 ]

A dummy zero bit is sent preceding the data during a read transfer by the
Microchip 93LC46B eeprom (section 2.7 of[1]). This results in right shift
of data during a read. In order to ignore this bit a quirk can be added to
send an extra zero bit after the read address.

Add a quirk to ignore the zero bit sent before data by adding a zero bit
after the read address.

[1] - https://www.mouser.com/datasheet/2/268/20001749K-277859.pdf

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Link: https://lore.kernel.org/r/20210105105817.17644-3-a-govindraju@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/misc/eeprom/eeprom_93xx46.c | 15 +++++++++++++++
include/linux/eeprom_93xx46.h | 2 ++
2 files changed, 17 insertions(+)

diff --git a/drivers/misc/eeprom/eeprom_93xx46.c b/drivers/misc/eeprom/eeprom_93xx46.c
index d92c4d2c521a..6e5f544c9c73 100644
--- a/drivers/misc/eeprom/eeprom_93xx46.c
+++ b/drivers/misc/eeprom/eeprom_93xx46.c
@@ -35,6 +35,10 @@ static const struct eeprom_93xx46_devtype_data atmel_at93c46d_data = {
EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH,
};

+static const struct eeprom_93xx46_devtype_data microchip_93lc46b_data = {
+ .quirks = EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE,
+};
+
struct eeprom_93xx46_dev {
struct spi_device *spi;
struct eeprom_93xx46_platform_data *pdata;
@@ -55,6 +59,11 @@ static inline bool has_quirk_instruction_length(struct eeprom_93xx46_dev *edev)
return edev->pdata->quirks & EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH;
}

+static inline bool has_quirk_extra_read_cycle(struct eeprom_93xx46_dev *edev)
+{
+ return edev->pdata->quirks & EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE;
+}
+
static int eeprom_93xx46_read(void *priv, unsigned int off,
void *val, size_t count)
{
@@ -96,6 +105,11 @@ static int eeprom_93xx46_read(void *priv, unsigned int off,
dev_dbg(&edev->spi->dev, "read cmd 0x%x, %d Hz\n",
cmd_addr, edev->spi->max_speed_hz);

+ if (has_quirk_extra_read_cycle(edev)) {
+ cmd_addr <<= 1;
+ bits += 1;
+ }
+
spi_message_init(&m);

t[0].tx_buf = (char *)&cmd_addr;
@@ -363,6 +377,7 @@ static void select_deassert(void *context)
static const struct of_device_id eeprom_93xx46_of_table[] = {
{ .compatible = "eeprom-93xx46", },
{ .compatible = "atmel,at93c46d", .data = &atmel_at93c46d_data, },
+ { .compatible = "microchip,93lc46b", .data = &microchip_93lc46b_data, },
{}
};
MODULE_DEVICE_TABLE(of, eeprom_93xx46_of_table);
diff --git a/include/linux/eeprom_93xx46.h b/include/linux/eeprom_93xx46.h
index eec7928ff8fe..99580c22f91a 100644
--- a/include/linux/eeprom_93xx46.h
+++ b/include/linux/eeprom_93xx46.h
@@ -16,6 +16,8 @@ struct eeprom_93xx46_platform_data {
#define EEPROM_93XX46_QUIRK_SINGLE_WORD_READ (1 << 0)
/* Instructions such as EWEN are (addrlen + 2) in length. */
#define EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH (1 << 1)
+/* Add extra cycle after address during a read */
+#define EEPROM_93XX46_QUIRK_EXTRA_READ_CYCLE BIT(2)

/*
* optional hooks to control additional logic
--
2.30.1