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misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom

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[ 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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
This commit is contained in:
Aswath Govindraju 2021-01-05 16:28:12 +05:30 • committed by Greg Kroah-Hartman
commit 1d113893ff
2 changed files with 17 additions and 0 deletions
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15
drivers/misc/eeprom/eeprom_93xx46.c
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@ -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);