linux-kernel - [PATCH RFC 4/4] i2c: at91: take slave mode capabilities of hardware into account

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Date:   Fri, 27 Oct 2017 17:12:17 +0200
From:   Juergen Fitschen <me@....yt>
To:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH RFC 4/4] i2c: at91: take slave mode capabilities of hardware
 into account

Some AT91 hardware has no slave mode included or only limited features
(i.e. no fifos).

Signed-off-by: Juergen Fitschen <me@....yt>
---
 drivers/i2c/busses/i2c-at91-core.c | 14 ++++++++++++--
 drivers/i2c/busses/i2c-at91.h      |  5 +++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index 3d7287c..9bf1e9d 100644
--- a/drivers/i2c/busses/i2c-at91-core.c
+++ b/drivers/i2c/busses/i2c-at91-core.c
@@ -69,6 +69,7 @@ void at91_init_twi_bus(struct at91_twi_dev *dev)
 static struct at91_twi_pdata at91rm9200_config = {
 	.clk_max_div = 5,
 	.clk_offset = 3,
+	.slave_mode_features = 0,
 	.has_unre_flag = true,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -77,6 +78,7 @@ static struct at91_twi_pdata at91rm9200_config = {
 static struct at91_twi_pdata at91sam9261_config = {
 	.clk_max_div = 5,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -85,6 +87,7 @@ static struct at91_twi_pdata at91sam9261_config = {
 static struct at91_twi_pdata at91sam9260_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -93,6 +96,7 @@ static struct at91_twi_pdata at91sam9260_config = {
 static struct at91_twi_pdata at91sam9g20_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -101,6 +105,7 @@ static struct at91_twi_pdata at91sam9g20_config = {
 static struct at91_twi_pdata at91sam9g10_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -131,6 +136,7 @@ static const struct platform_device_id at91_twi_devtypes[] = {
 static struct at91_twi_pdata at91sam9x5_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = false,
@@ -139,6 +145,7 @@ static struct at91_twi_pdata at91sam9x5_config = {
 static struct at91_twi_pdata sama5d4_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE,
 	.has_unre_flag = false,
 	.has_alt_cmd = false,
 	.has_hold_field = true,
@@ -147,6 +154,7 @@ static struct at91_twi_pdata sama5d4_config = {
 static struct at91_twi_pdata sama5d2_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
+	.slave_mode_features = AT91_TWI_SM_AVAILABLE | AT91_TWI_SM_HAS_FIFO | AT91_TWI_SM_CAN_NACK,
 	.has_unre_flag = true,
 	.has_alt_cmd = true,
 	.has_hold_field = true,
@@ -219,6 +227,10 @@ static int at91_twi_probe(struct platform_device *pdev)
 	if (!dev->pdata)
 		return -ENODEV;
 
+	dev->slave_detected = i2c_detect_slave_mode(&pdev->dev);
+	if (dev->slave_detected && dev->pdata->slave_mode_features == 0)
+		return -EPFNOSUPPORT;
+
 	dev->base = devm_ioremap_resource(&pdev->dev, mem);
 	if (IS_ERR(dev->base))
 		return PTR_ERR(dev->base);
@@ -245,8 +257,6 @@ static int at91_twi_probe(struct platform_device *pdev)
 	dev->adapter.timeout = AT91_I2C_TIMEOUT;
 	dev->adapter.dev.of_node = pdev->dev.of_node;
 
-	dev->slave_detected = i2c_detect_slave_mode(&pdev->dev);
-
 	if (dev->slave_detected)
 		rc = at91_twi_probe_slave(pdev, phy_addr, dev);
 	else
diff --git a/drivers/i2c/busses/i2c-at91.h b/drivers/i2c/busses/i2c-at91.h
index bb502c1..4a4fa67 100644
--- a/drivers/i2c/busses/i2c-at91.h
+++ b/drivers/i2c/busses/i2c-at91.h
@@ -107,9 +107,14 @@
 
 #define	AT91_TWI_VER		0x00fc	/* Version Register */
 
+#define	AT91_TWI_SM_AVAILABLE	BIT(0)	/* Slave mode supported */
+#define	AT91_TWI_SM_CAN_NACK	BIT(1)	/* Can send NACKs in slave mode */
+#define	AT91_TWI_SM_HAS_FIFO	BIT(2)	/* Has FIFO for slave mode */
+
 struct at91_twi_pdata {
 	unsigned clk_max_div;
 	unsigned clk_offset;
+	unsigned slave_mode_features;
 	bool has_unre_flag;
 	bool has_alt_cmd;
 	bool has_hold_field;
-- 
2.7.4