NFC: trf7970a: Add device tree option of 1.8 Volt IO voltage

The TRF7970A has configuration options for supporting hardware designs
with 1.8 Volt or 3.3 Volt IO.   This commit adds a device tree option,
using a fixed regulator binding, for setting the io voltage to match
the hardware configuration. If no option is supplied it defaults to
3.3 volt configuration.

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Geoff Lansberry <geoff@kuvee.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

2 files changed, 27 insertions, 1 deletions

diff --git a/Documentation/devicetree/bindings/net/nfc/trf7970a.txt b/Documentation/devicetree/bindings/net/nfc/trf7970a.txt
index 1d186cd9817b..c627bbb3009e 100644
--- a/Documentation/devicetree/bindings/net/nfc/trf7970a.txt
+++ b/Documentation/devicetree/bindings/net/nfc/trf7970a.txt
@@ -21,6 +21,7 @@ Optional SoC Specific Properties:
 - t5t-rmb-extra-byte-quirk: Specify that the trf7970a has the erratum
   where an extra byte is returned by Read Multiple Block commands issued
   to Type 5 tags.
+- vdd-io-supply: Regulator specifying voltage for vdd-io
 - clock-frequency: Set to specify that the input frequency to the trf7970a is 13560000Hz or 27120000Hz
 
 Example (for ARM-based BeagleBone with TRF7970A on SPI1):
@@ -40,6 +41,7 @@ Example (for ARM-based BeagleBone with TRF7970A on SPI1):
                                   <&gpio2 5 GPIO_ACTIVE_LOW>;
                 vin-supply = <&ldo3_reg>;
                 vin-voltage-override = <5000000>;
+                vdd-io-supply = <&ldo2_reg>;
                 autosuspend-delay = <30000>;
                 irq-status-read-quirk;
                 en2-rf-quirk;
diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index ecb786283ffa..2d1c8ca6e679 100644
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -444,6 +444,7 @@ struct trf7970a {
         u8                              iso_ctrl_tech;
         u8                              modulator_sys_clk_ctrl;
         u8                              special_fcn_reg1;
+        u8                              io_ctrl;
         unsigned int                    guard_time;
         int                             technology;
         int                             framing;
@@ -1051,6 +1052,11 @@ static int trf7970a_init(struct trf7970a *trf)
         if (ret)
                 goto err_out;
 
+        ret = trf7970a_write(trf, TRF7970A_REG_IO_CTRL,
+                        trf->io_ctrl | TRF7970A_REG_IO_CTRL_VRS(0x1));
+        if (ret)
+                goto err_out;
+
         ret = trf7970a_write(trf, TRF7970A_NFC_TARGET_LEVEL, 0);
         if (ret)
                 goto err_out;
@@ -1767,7 +1773,7 @@ static int _trf7970a_tg_listen(struct nfc_digital_dev *ddev, u16 timeout,
                 goto out_err;
 
         ret = trf7970a_write(trf, TRF7970A_REG_IO_CTRL,
-                        TRF7970A_REG_IO_CTRL_VRS(0x1));
+                        trf->io_ctrl | TRF7970A_REG_IO_CTRL_VRS(0x1));
         if (ret)
                 goto out_err;
 
@@ -2107,6 +2113,24 @@ static int trf7970a_probe(struct spi_device *spi)
         if (uvolts > 4000000)
                 trf->chip_status_ctrl = TRF7970A_CHIP_STATUS_VRS5_3;
 
+        trf->regulator = devm_regulator_get(&spi->dev, "vdd-io");
+        if (IS_ERR(trf->regulator)) {
+                ret = PTR_ERR(trf->regulator);
+                dev_err(trf->dev, "Can't get VDD_IO regulator: %d\n", ret);
+                goto err_destroy_lock;
+        }
+
+        ret = regulator_enable(trf->regulator);
+        if (ret) {
+                dev_err(trf->dev, "Can't enable VDD_IO: %d\n", ret);
+                goto err_destroy_lock;
+        }
+
+        if (regulator_get_voltage(trf->regulator) == 1800000) {
+                trf->io_ctrl = TRF7970A_REG_IO_CTRL_IO_LOW;
+                dev_dbg(trf->dev, "trf7970a config vdd_io to 1.8V\n");
+        }
+
         trf->ddev = nfc_digital_allocate_device(&trf7970a_nfc_ops,
                         TRF7970A_SUPPORTED_PROTOCOLS,
                         NFC_DIGITAL_DRV_CAPS_IN_CRC |