diff options
| author | Parker Newman <pnewman@connecttech.com> | 2024-10-02 18:12:33 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-14 22:00:16 +0300 |
| commit | 3fbde702748db366d9cbd25938cd7c6cdb15854a (patch) | |
| tree | e2a3c52846687a71bd56a123214e146a5d380d77 /drivers/misc | |
| parent | 691284c2cd33ffaa0b35ce53b3286b90621e9dc9 (diff) | |
| download | linux-3fbde702748db366d9cbd25938cd7c6cdb15854a.tar.xz | |
misc: eeprom: eeprom_93cx6: Add quirk for extra read clock cycle
[ Upstream commit 7738a7ab9d12c5371ed97114ee2132d4512e9fd5 ]
Add a quirk similar to eeprom_93xx46 to add an extra clock cycle before
reading data from the EEPROM.
The 93Cx6 family of EEPROMs output a "dummy 0 bit" between the writing
of the op-code/address from the host to the EEPROM and the reading of
the actual data from the EEPROM.
More info can be found on page 6 of the AT93C46 datasheet (linked below).
Similar notes are found in other 93xx6 datasheets.
In summary the read operation for a 93Cx6 EEPROM is:
Write to EEPROM: 110[A5-A0] (9 bits)
Read from EEPROM: 0[D15-D0] (17 bits)
Where:
110 is the start bit and READ OpCode
[A5-A0] is the address to read from
0 is a "dummy bit" preceding the actual data
[D15-D0] is the actual data.
Looking at the READ timing diagrams in the 93Cx6 datasheets the dummy
bit should be clocked out on the last address bit clock cycle meaning it
should be discarded naturally.
However, depending on the hardware configuration sometimes this dummy
bit is not discarded. This is the case with Exar PCI UARTs which require
an extra clock cycle between sending the address and reading the data.
Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-5193-SEEPROM-AT93C46D-Datasheet.pdf
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Parker Newman <pnewman@connecttech.com>
Link: https://lore.kernel.org/r/0f23973efefccd2544705a0480b4ad4c2353e407.1727880931.git.pnewman@connecttech.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/misc')
| -rw-r--r-- | drivers/misc/eeprom/eeprom_93cx6.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/misc/eeprom/eeprom_93cx6.c b/drivers/misc/eeprom/eeprom_93cx6.c index 9627294fe3e9..4c9827fe9217 100644 --- a/drivers/misc/eeprom/eeprom_93cx6.c +++ b/drivers/misc/eeprom/eeprom_93cx6.c @@ -186,6 +186,11 @@ void eeprom_93cx6_read(struct eeprom_93cx6 *eeprom, const u8 word, eeprom_93cx6_write_bits(eeprom, command, PCI_EEPROM_WIDTH_OPCODE + eeprom->width); + if (has_quirk_extra_read_cycle(eeprom)) { + eeprom_93cx6_pulse_high(eeprom); + eeprom_93cx6_pulse_low(eeprom); + } + /* * Read the requested 16 bits. */ @@ -252,6 +257,11 @@ void eeprom_93cx6_readb(struct eeprom_93cx6 *eeprom, const u8 byte, eeprom_93cx6_write_bits(eeprom, command, PCI_EEPROM_WIDTH_OPCODE + eeprom->width + 1); + if (has_quirk_extra_read_cycle(eeprom)) { + eeprom_93cx6_pulse_high(eeprom); + eeprom_93cx6_pulse_low(eeprom); + } + /* * Read the requested 8 bits. */ |