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Kernel: Fixed fdc read/write problem

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Fixed an issue with operator precedence in calls to `send_byte()`, in
which a value of `1` was being sent to the function. This had the
nasty side-effect of selecting the slave drive if the value of
`head` was equal to one. A read/write would fail in the case, as
it would attempt to read from the slave drive (not good).

I've also added a seek to the top of the read/write code, which seems
to have fixed an issue with Linux not detecting the disk images after
they have been unmounted from Serenity. This isn't specified in the
datasheet, but a few other drivers have it so we should too :^)
This commit is contained in:
Jesse Buhagiar 2019-10-21 01:04:08 +11:00 committed by Andreas Kling
parent 98c86e5109
commit c12d153894
Notes: sideshowbarker 2024-07-19 11:34:34 +09:00 
Author: https://github.com/Quaker762 🔰
Commit: https://github.com/SerenityOS/serenity/commit/c12d1538945
Pull-request: https://github.com/SerenityOS/serenity/pull/676
Reviewed-by: https://github.com/awesomekling
2 changed files with 49 additions and 17 deletions
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58
Kernel/Devices/FloppyDiskDevice.cpp
View file

@ -122,9 +122,14 @@ bool FloppyDiskDevice::read_sectors_with_dma(u16 lba, u16 count, u8* outbuf)
kprintf("fdc: read_sectors_with_dma lba = %d count = %d\n", lba, count);
#endif
motor_enable(is_slave() ? 1 : 0); // Should I bother casting this?!
motor_enable(is_slave()); // Should I bother casting this?!
write_ccr(0);
recalibrate(); // Recalibrate the drive
recalibrate();
if (!seek(lba)) {
kprintf("fdc: failed to seek to lba = %d!\n", lba);
return false;
}
// We have to wait for about 300ms for the drive to spin up, because of
// the inertia of the motor and diskette. This is only
@ -155,13 +160,13 @@ bool FloppyDiskDevice::read_sectors_with_dma(u16 lba, u16 count, u8* outbuf)
for (int i = 0; i < 3; i++) {
// Now actually send the command to the drive. This is a big one!
send_byte(FLOPPY_MFM | FLOPPY_MT | FLOPPY_SK | static_cast<u8>(FloppyCommand::ReadData));
send_byte(head << 2 | is_slave() ? 1 : 0);
send_byte((head << 2) | is_slave());
send_byte(cylinder);
send_byte(head);
send_byte(sector);
send_byte(SECTORS_PER_CYLINDER >> 8); // Yikes!
send_byte((sector + 1) >= SECTORS_PER_CYLINDER ? SECTORS_PER_CYLINDER : sector + 1);
send_byte(0x27); // GPL3 value. The Datasheet doesn't really specify the values for this properly...
send_byte(((sector + 1) >= SECTORS_PER_CYLINDER) ? SECTORS_PER_CYLINDER : sector + 1);
send_byte(0x1b); // GPL3 value. The Datasheet doesn't really specify the values for this properly...
send_byte(0xff);
enable_irq();
@ -170,8 +175,20 @@ bool FloppyDiskDevice::read_sectors_with_dma(u16 lba, u16 count, u8* outbuf)
m_interrupted = false;
// Flush FIFO
read_byte();
read_byte();
// Let's check the value of Status Register 1 to ensure that
// the command executed correctly
u8 cmd_st0 = read_byte();
if ((cmd_st0 & 0xc0) != 0) {
kprintf("fdc: read failed with error code (st0) 0x%x\n", cmd_st0 >> 6);
return false;
}
u8 cmd_st1 = read_byte();
if (cmd_st1 != 0) {
kprintf("fdc: read failed with error code (st1) 0x%x\n", cmd_st1);
return false;
}
read_byte();
u8 cyl = read_byte();
read_byte();
@ -214,6 +231,11 @@ bool FloppyDiskDevice::write_sectors_with_dma(u16 lba, u16 count, const u8* inbu
write_ccr(0);
recalibrate(); // Recalibrate the drive
if (!seek(lba)) {
kprintf("fdc: failed to seek to lba = %d!\n", lba);
return false;
}
// We have to wait for about 300ms for the drive to spin up, because of
// the inertia of the motor and diskette.
// TODO: Fix this abomination please!
@ -238,13 +260,13 @@ bool FloppyDiskDevice::write_sectors_with_dma(u16 lba, u16 count, const u8* inbu
for (int i = 0; i < 3; i++) {
// Now actually send the command to the drive. This is a big one!
send_byte(FLOPPY_MFM | FLOPPY_MT | static_cast<u8>(FloppyCommand::WriteData));
send_byte(head << 2 | is_slave() ? 1 : 0);
send_byte(head << 2 | is_slave());
send_byte(cylinder);
send_byte(head);
send_byte(sector);
send_byte(SECTORS_PER_CYLINDER >> 8); // Yikes!
send_byte((sector + 1) >= SECTORS_PER_CYLINDER ? SECTORS_PER_CYLINDER : sector + 1);
send_byte(0x27); // GPL3 value. The Datasheet doesn't really specify the values for this properly...
send_byte(0x1b); // GPL3 value. The Datasheet doesn't really specify the values for this properly...
send_byte(0xff);
enable_irq();
@ -253,8 +275,18 @@ bool FloppyDiskDevice::write_sectors_with_dma(u16 lba, u16 count, const u8* inbu
m_interrupted = false;
// Flush FIFO
read_byte();
read_byte();
u8 cmd_st0 = read_byte();
if ((cmd_st0 & 0xc0) != 0) {
kprintf("fdc: write failed! Error code 0x%x\n", cmd_st0 >> 6);
return false;
}
u8 cmd_st1 = read_byte();
if (cmd_st1 != 0) {
kprintf("fdc: write failed with error code (st1) 0x%x\n", cmd_st1);
return false;
}
read_byte();
u8 cyl = read_byte();
read_byte();
@ -385,7 +417,7 @@ bool FloppyDiskDevice::recalibrate()
kprintf("fdc: recalibrating drive...\n");
#endif
u8 slave = is_slave() ? 1 : 0;
u8 slave = is_slave();
motor_enable(slave);
for (int i = 0; i < 16; i++) {
@ -413,7 +445,7 @@ bool FloppyDiskDevice::seek(u16 lba)
{
u8 head = lba2head(lba) & 0x01;
u8 cylinder = lba2cylinder(lba) & 0xff;
u8 slave = is_slave() ? 1 : 0;
u8 slave = is_slave();
// First, we need to enable the correct drive motor
motor_enable(slave);

8
Kernel/Devices/FloppyDiskDevice.h
View file

@ -101,7 +101,7 @@ class FloppyDiskDevice final : public IRQHandler
AK_MAKE_ETERNAL
static constexpr u8 SECTORS_PER_CYLINDER = 18;
static constexpr u8 CCYLINDERS_PER_HEAD = 80;
static constexpr u8 CYLINDERS_PER_HEAD = 80;
static constexpr u16 BYTES_PER_SECTOR = 512;
public:
@ -158,9 +158,9 @@ private:
virtual const char* class_name() const override;
// Helper functions
inline u16 lba2cylinder(u16 lba) const { return lba / (2 * SECTORS_PER_CYLINDER); } // Convert an LBA into a cylinder value
inline u16 lba2head(u16 lba) const { return ((lba / SECTORS_PER_CYLINDER) % 2); } // Convert an LBA into a head value
inline u16 lba2sector(u16 lba) const { return ((lba % SECTORS_PER_CYLINDER) + 1); } // Convert an LBA into a sector value
inline u16 lba2head(u16 lba) const { return (lba % (SECTORS_PER_CYLINDER * 2)) / SECTORS_PER_CYLINDER; } // Convert an LBA into a head value
inline u16 lba2cylinder(u16 lba) const { return lba / (2 * SECTORS_PER_CYLINDER); } // Convert an LBA into a cylinder value
inline u16 lba2sector(u16 lba) const { return ((lba % SECTORS_PER_CYLINDER) + 1); } // Convert an LBA into a sector value
void initialize();
bool read_sectors_with_dma(u16, u16, u8*);