[PATCH v2 0/2] eeprom: eeprom_93xx46: Add support for microchip 93LC46B eeprom

[PATCH v2 0/2] eeprom: eeprom_93xx46: Add support for microchip 93LC46B eeprom

[Aswath Govindraju]

This series of patches adds support for microchip 93LC46B eeprom by
 - Adding a new compatible string
 - Adding a quirk to send extra bit after the address to ignore the
   zero bit sent before data, during a read transfer.

changes since v1:
- changed the compatible string to lower case.
- changed the variable for private data to lower case.

Aswath Govindraju (2):
  Documentation: devicetree: Add new compatible string for eeprom
    microchip 93LC46B
  misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom

 .../devicetree/bindings/misc/eeprom-93xx46.txt    |  1 +
 drivers/misc/eeprom/eeprom_93xx46.c               | 15 +++++++++++++++
 include/linux/eeprom_93xx46.h                     |  2 ++
 3 files changed, 18 insertions(+)

-- 
2.17.1

[PATCH v2 1/2] Documentation: devicetree: Add new compatible string for eeprom microchip 93LC46B

[Aswath Govindraju]

Add a new compatible string for eeprom microchip 93LC46B in eeprom-93xx46
dt-binding file as it belongs to the 93xx46 family of devices.

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
---
 Documentation/devicetree/bindings/misc/eeprom-93xx46.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt b/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
index a8ebb4621f79..7b636b7a8311 100644
--- a/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
+++ b/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
@@ -4,6 +4,7 @@ Required properties:
 - compatible : shall be one of:
     "atmel,at93c46d"
     "eeprom-93xx46"
+    "microchip,93lc46b"
 - data-size : number of data bits per word (either 8 or 16)
 
 Optional properties:
-- 
2.17.1

Re: [PATCH v2 1/2] Documentation: devicetree: Add new compatible string for eeprom microchip 93LC46B

[Rob Herring]

On Tue, 05 Jan 2021 16:28:11 +0530, Aswath Govindraju wrote:
> Add a new compatible string for eeprom microchip 93LC46B in eeprom-93xx46
> dt-binding file as it belongs to the 93xx46 family of devices.
> 
> Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
> ---
>  Documentation/devicetree/bindings/misc/eeprom-93xx46.txt | 1 +
>  1 file changed, 1 insertion(+)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v2 2/2] misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom

[Aswath Govindraju]

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>
---
 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 7c45f82b4302..a18247696ce7 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
-- 
2.17.1