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Fix reading EDID on TVs/monitors without E-DCC support

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Writing segment id to I2C device 0x30 only required if the segment is
non-zero. On the devices without E-DCC support writing to that address
fails and whole transaction then fails too. To avoid this do
not attempt write to the segment selection device unless required.

MFC after:	2 weeks
This commit is contained in:
Oleksandr Tymoshenko 2020-06-10 21:38:35 +00:00
parent 9b6b2f8608
commit cbc596d6bf
1 changed files with 6 additions and 1 deletions
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7
sys/dev/hdmi/dwc_hdmi.c
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@ -658,6 +658,11 @@ hdmi_edid_read(struct dwc_hdmi_softc *sc, int block, uint8_t **edid,
int result;
uint8_t addr = block & 1 ? EDID_LENGTH : 0;
uint8_t segment = block >> 1;
/*
* Some devices do not support E-DDC so attempt
* writing segment address only if it's neccessary
*/
unsigned char xfers = segment ? 3 : 2;
struct iic_msg msg[] = {
{ I2C_DDC_SEGADDR, IIC_M_WR, 1, &segment },
{ I2C_DDC_ADDR, IIC_M_WR, 1, &addr },
@ -687,7 +692,7 @@ hdmi_edid_read(struct dwc_hdmi_softc *sc, int block, uint8_t **edid,
return (result);
}
result = iicbus_transfer(i2c_dev, msg, 3);
result = iicbus_transfer(i2c_dev, &msg[3 - xfers], xfers);
iicbus_release_bus(i2c_dev, sc->sc_dev);
if (result) {