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qi-fix-i2c-multiread-nack-nak.patch
On the last read, master must NAK, on intermediate reads it must ACK. If you get this wrong, communication with device is screwed even in Linux. Signed-off-by: Andy Green <andy@openmoko.com>
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@ -53,14 +53,17 @@ int i2c_next_state(struct i2c_bitbang * bb)
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case IBS_INIT:
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bb->index = 0;
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bb->index_read = 0;
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/* fall thru */
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(bb->set)(1, 1);
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bb->state = IBS_START1;
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break;
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case IBS_START1:
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(bb->set)(1, 0);
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(bb->set)(0, 0); /* start */
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bb->state = IBS_START2;
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break;
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case IBS_START2:
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(bb->set)(0, 0); /* start */
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bb->count = 8;
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bb->state = IBS_ADS_TX_S;
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break;
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@ -137,25 +140,34 @@ int i2c_next_state(struct i2c_bitbang * bb)
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case IBS_DATA_RX_L:
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bb->data[bb->index_read] <<= 1;
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bb->data[bb->index_read] |= !!(bb->read_sda)();
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(bb->set)(0, 1);
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bb->count--;
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if (bb->count) {
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(bb->set)(0, 1);
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bb->state = IBS_DATA_RX_S;
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break;
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}
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/* slave has released SDA now, bang down ACK */
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(bb->set)(0, 0);
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if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
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(bb->set)(0, 1);
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else
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(bb->set)(0, 0);
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bb->state = IBS_DATA_RX_ACK_H;
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break;
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case IBS_DATA_RX_ACK_H:
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(bb->set)(1, 0);
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if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
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(bb->set)(1, 1); /* NAK */
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else
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(bb->set)(1, 0); /* ACK */
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bb->state = IBS_DATA_RX_ACK_L;
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break;
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case IBS_DATA_RX_ACK_L:
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(bb->set)(0, 1);
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if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
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(bb->set)(0, 1); /* NAK */
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else
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(bb->set)(0, 0); /* ACK */
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bb->index_read++;
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bb->index++;
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switch (bb->data[bb->index]) {
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@ -214,6 +226,11 @@ static int i2c_complete_synchronously(struct i2c_bitbang * bb)
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(bb->spin)();
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}
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if (ret < 0) {
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puts("i2c transaction failed ");
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printdec(ret);
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puts("\n");
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}
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return ret;
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}
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