NFC: trf7970a: Add RF technology specific guard times

When turning on the RF field, the driver must wait
an RF-technology-specific amount of time (known as
the guard time) before modulating the field.
Currently, the driver waits 5 ms but that is too
short for NFCF and too long for ISO/IEC 15693.
Fix this by determining the guard time when the
RF technology is set and delaying that amount
of time when turning on the RF field.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c
index ce9686c..22485e7 100644 (file)
--- a/drivers/nfc/trf7970a.c
+++ b/drivers/nfc/trf7970a.c
@@ -134,6 +134,12 @@
 #define TRF7970A_WAIT_FOR_FIFO_DRAIN_TIMEOUT   3
 #define TRF7970A_WAIT_TO_ISSUE_ISO15693_EOF    20
 
+/* Guard times for various RF technologies (in us) */
+#define TRF7970A_GUARD_TIME_NFCA               5000
+#define TRF7970A_GUARD_TIME_NFCB               5000
+#define TRF7970A_GUARD_TIME_NFCF               20000
+#define TRF7970A_GUARD_TIME_15693              1000
+
 /* Quirks */
 /* Erratum: When reading IRQ Status register on trf7970a, we must issue a
  * read continuous command for IRQ Status and Collision Position registers.
@@ -351,6 +357,7 @@ struct trf7970a {
        u8                              iso_ctrl_tech;
        u8                              modulator_sys_clk_ctrl;
        u8                              special_fcn_reg1;
+       unsigned int                    guard_time;
        int                             technology;
        int                             framing;
        u8                              tx_cmd;
@@ -887,22 +894,27 @@ static int trf7970a_config_rf_tech(struct trf7970a *trf, int tech)
        case NFC_DIGITAL_RF_TECH_106A:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_14443A_106;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_OOK;
+               trf->guard_time = TRF7970A_GUARD_TIME_NFCA;
                break;
        case NFC_DIGITAL_RF_TECH_106B:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_14443B_106;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
+               trf->guard_time = TRF7970A_GUARD_TIME_NFCB;
                break;
        case NFC_DIGITAL_RF_TECH_212F:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_FELICA_212;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
+               trf->guard_time = TRF7970A_GUARD_TIME_NFCF;
                break;
        case NFC_DIGITAL_RF_TECH_424F:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_FELICA_424;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
+               trf->guard_time = TRF7970A_GUARD_TIME_NFCF;
                break;
        case NFC_DIGITAL_RF_TECH_ISO15693:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_15693_SGL_1OF4_2648;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_OOK;
+               trf->guard_time = TRF7970A_GUARD_TIME_15693;
                break;
        default:
                dev_dbg(trf->dev, "Unsupported rf technology: %d\n", tech);
@@ -971,7 +983,7 @@ static int trf7970a_config_framing(struct trf7970a *trf, int framing)
 
                trf->chip_status_ctrl |= TRF7970A_CHIP_STATUS_RF_ON;
 
-               usleep_range(5000, 6000);
+               usleep_range(trf->guard_time, trf->guard_time + 1000);
        }
 
        return 0;