usb: typec: fsa4480: Check if the chip is really there

Currently, the driver will happily register the switch/mux devices, and
so long as the i2c master doesn't complain, the user would never know
there's something wrong.

Add a device id check (based on [1]) and return -ENODEV if the read
fails or returns nonsense.

Checking the value on a Qualcomm SM6115P-based Lenovo Tab P11 tablet,
the ID mentioned in the datasheet does indeed show up:
 fsa4480 1-0042: Found FSA4480 v1.1 (Vendor ID = 0)

[1] https://www.onsemi.com/pdf/datasheet/fsa4480-d.pdf

Fixes: 1dc246320c6b ("usb: typec: mux: Add On Semi fsa4480 driver")
Cc: stable <stable@kernel.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240729-topic-fs4480_check-v3-1-f5bf732d3424@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/mux/fsa4480.c b/drivers/usb/typec/mux/fsa4480.c
index cb7cdf90cb0aaa4184602ed2dab3f4e4382901ea..cd235339834b0b8aa0492e9eb194e283dc5b0958 100644 (file)
--- a/drivers/usb/typec/mux/fsa4480.c
+++ b/drivers/usb/typec/mux/fsa4480.c
@@ -13,6 +13,10 @@
 #include <linux/usb/typec_dp.h>
 #include <linux/usb/typec_mux.h>
 
+#define FSA4480_DEVICE_ID      0x00
+ #define FSA4480_DEVICE_ID_VENDOR_ID   GENMASK(7, 6)
+ #define FSA4480_DEVICE_ID_VERSION_ID  GENMASK(5, 3)
+ #define FSA4480_DEVICE_ID_REV_ID      GENMASK(2, 0)
 #define FSA4480_SWITCH_ENABLE  0x04
 #define FSA4480_SWITCH_SELECT  0x05
 #define FSA4480_SWITCH_STATUS1 0x07
@@ -251,6 +255,7 @@ static int fsa4480_probe(struct i2c_client *client)
        struct typec_switch_desc sw_desc = { };
        struct typec_mux_desc mux_desc = { };
        struct fsa4480 *fsa;
+       int val = 0;
        int ret;
 
        fsa = devm_kzalloc(dev, sizeof(*fsa), GFP_KERNEL);
@@ -268,6 +273,15 @@ static int fsa4480_probe(struct i2c_client *client)
        if (IS_ERR(fsa->regmap))
                return dev_err_probe(dev, PTR_ERR(fsa->regmap), "failed to initialize regmap\n");
 
+       ret = regmap_read(fsa->regmap, FSA4480_DEVICE_ID, &val);
+       if (ret || !val)
+               return dev_err_probe(dev, -ENODEV, "FSA4480 not found\n");
+
+       dev_dbg(dev, "Found FSA4480 v%lu.%lu (Vendor ID = %lu)\n",
+               FIELD_GET(FSA4480_DEVICE_ID_VERSION_ID, val),
+               FIELD_GET(FSA4480_DEVICE_ID_REV_ID, val),
+               FIELD_GET(FSA4480_DEVICE_ID_VENDOR_ID, val));
+
        /* Safe mode */
        fsa->cur_enable = FSA4480_ENABLE_DEVICE | FSA4480_ENABLE_USB;
        fsa->mode = TYPEC_STATE_SAFE;