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Kernel/Storage: Wait a few microseconds after selecting the IDE drive

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We need to do it to let real hardware to put the correct voltages
on the wire.
Apparently my ICH7 machine refused to boot, and was reading lots of
garbage from an unconnected IDE channel. It was fixed after I added a
delay of 20 microseconds. It probably can be reduced, I just took a safe
value and it seems to work correctly without any problems :)
This commit is contained in:
Liav A 2021-04-05 21:24:05 +03:00 committed by Andreas Kling
parent 210754a93a
commit da109eeab8
Notes: sideshowbarker 2024-07-18 20:40:31 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/da109eeab81
Pull-request: https://github.com/SerenityOS/serenity/pull/6121
Reviewed-by: https://github.com/tomuta
1 changed files with 8 additions and 0 deletions
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8
Kernel/Storage/IDEChannel.cpp
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@ -288,8 +288,14 @@ UNMAP_AFTER_INIT void IDEChannel::detect_disks()
// There are only two possible disks connected to a channel
for (auto i = 0; i < 2; i++) {
// We need to select the drive and then we wait 20 microseconds... and it doesn't hurt anything so let's just do it.
m_io_group.io_base().offset(ATA_REG_HDDEVSEL).out<u8>(0xA0 | (i << 4)); // First, we need to select the drive itself
IO::delay(20);
m_io_group.io_base().offset(ATA_REG_SECCOUNT0).out<u8>(0);
m_io_group.io_base().offset(ATA_REG_LBA0).out<u8>(0);
m_io_group.io_base().offset(ATA_REG_LBA1).out<u8>(0);
m_io_group.io_base().offset(ATA_REG_LBA2).out<u8>(0);
m_io_group.io_base().offset(ATA_REG_COMMAND).out<u8>(ATA_CMD_IDENTIFY); // Send the ATA_IDENTIFY command
// Wait for the BSY flag to be reset
@ -389,7 +395,9 @@ void IDEChannel::ata_access(Direction direction, bool slave_request, u64 lba, u8
wait_until_not_busy();
// We need to select the drive and then we wait 20 microseconds... and it doesn't hurt anything so let's just do it.
m_io_group.io_base().offset(ATA_REG_HDDEVSEL).out<u8>(0xE0 | (static_cast<u8>(slave_request) << 4) | head);
IO::delay(20);
if (lba_mode == LBAMode::FortyEightBit) {
m_io_group.io_base().offset(ATA_REG_SECCOUNT1).out<u8>(0);