kernel: verify EEPROM calibration data

This commit verifies that the eeprom data makes sense. If an error is found, identity calibration is selected instead. Endian conversion is not there yet. Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

kernel: verify EEPROM calibration data
This commit verifies that the eeprom data makes sense. If an error is found, identity calibration is selected instead. Endian conversion is not there yet. Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
53dc6acd · Alessandro Rubini · da1e589a · 53dc6acd
Commit 53dc6acd authored Jul 02, 2013 by Alessandro Rubini
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fa-zio-drv.c kernel/fa-zio-drv.c +67 -1

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--- a/kernel/fa-zio-drv.c
+++ b/kernel/fa-zio-drv.c
@@ -971,6 +971,71 @@ struct fmc_gpio zfat_gpio_cfg[] = {
 	}
 };

+/* * * * * * * * * * * * * * * * Calibration checks * * * * * * * * * * * */
+
+/* This identity calibration is used as default */
+static struct fa_calib_stanza fa_identity_calib = {
+	.offset = { 0, },
+	.gain = {0x8000, 0x8000, 0x8000, 0x8000},
+	.temperature = 50 * 100, /* 50 celsius degrees */
+};
+/* Max difference from identity thing */
+#define FA_CALIB_MAX_DELTA_OFFSET	0x1000
+#define FA_CALIB_MAX_DELTA_GAIN		0x1000
+#define FA_CALIB_MAX_DELTA_TEMP		(40 * 100) /* 10-90 celsius */
+
+/* Actual verification code */
+static int zfad_verify_calib_stanza(struct device *msgdev, char *name, int r,
+				    struct fa_calib_stanza *cal,
+				    struct fa_calib_stanza *iden)
+{
+	int i, err = 0;
+
+	for (i = 0; i < ARRAY_SIZE(cal->offset); i++) {
+		if (abs(cal->offset[i] - iden->offset[i])
+		    > FA_CALIB_MAX_DELTA_OFFSET) {
+			dev_dbg(msgdev, "wrong offset 0x%x\n", cal->offset[i]);
+			err++;
+		}
+		if (abs((s16)(cal->gain[i] - iden->gain[i]))
+		    > FA_CALIB_MAX_DELTA_GAIN) {
+			dev_dbg(msgdev, "wrong gain   0x%x\n", cal->gain[i]);
+			err++;
+		}
+	}
+	if (abs((s16)(cal->temperature - iden->temperature))
+	    > FA_CALIB_MAX_DELTA_TEMP) {
+		dev_dbg(msgdev, "wrong temper 0x%x\n", cal->temperature);
+		err++;
+	}
+	if (err)
+		dev_dbg(msgdev, "%i errors in %s calibration, range %i\n",
+			err, name, r);
+	return err;
+}
+
+static void zfad_verify_calib(struct device *msgdev,
+			      struct fa_calib *calib,
+			      struct fa_calib_stanza *identity)
+{
+	int i, err = 0;
+
+	for (i = 0; i < ARRAY_SIZE(calib->adc); i++) {
+		err += zfad_verify_calib_stanza(msgdev, "adc", i,
+						calib->adc + i, identity);
+		err += zfad_verify_calib_stanza(msgdev, "dac", i,
+						calib->dac + i, identity);
+	}
+	if (!err)
+		return;
+
+	dev_info(msgdev, "Invalid calibration in EEPROM (%i errors)\n", err);
+	dev_info(msgdev, "Using identity calibration\n");
+	for (i = 0; i < ARRAY_SIZE(calib->adc); i++) {
+		calib->adc[i] = *identity;
+		calib->dac[i] = *identity;
+	}
+}

 /* * * * * * * * * * * * * * * * Initialization * * * * * * * * * * * * * * */

@@ -990,8 +1055,9 @@ static int zfad_zio_probe(struct zio_device *zdev)
 	/* Save also the pointer to the real zio_device */
 	fa->zdev = zdev;

-	/* Retrieve calibration data from the eeprom. FIXME: verify it */
+	/* Retrieve calibration data from the eeprom, then verify it */
 	memcpy(&fa->calib, fa->fmc->eeprom + FA_CAL_OFFSET, sizeof(fa->calib));
+	zfad_verify_calib(&fa->fmc->dev, &fa->calib, &fa_identity_calib);

 	/* Configure GPIO for IRQ */
 	fa->fmc->op->gpio_config(fa->fmc, zfat_gpio_cfg,