drm/amdgpu: Fix unnecessary else after return in 'amdgpu_eeprom_xfer'

Fixes the following:

WARNING: else is not generally useful after a break or return
+ return -EINVAL;
+ } else {

Cc: Guchun Chen <guchun.chen@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Allow non-standard EEPROM I2C address

Allow non-standard EEPROM I2C address of 0x58, where the Device Type
Identifier is 1011b, where we form 1011000b = 0x58 I2C address, as on some
ASICs the FRU data lives there.

Cc: Alex Deucher <Alexander.Deucher@amd.com>
Cc: Kent Russell <kent.russell@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Tested-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Remove redundant I2C EEPROM address

Remove redundant EEPROM_I2C_MADDR_54H address, since we already have it
represented (ARCTURUS), and since we don't include the I2C device type
identifier in EEPROM memory addresses, i.e. that high up in the device
abstraction--we only use EEPROM memory addresses, as memory is continuously
represented by EEPROM device(s) on the I2C bus.

Add a comment describing what these memory addresses are, how they come
about and how they're usually extracted from the device address byte.

Cc: Candice Li <candice.li@amd.com>
Cc: Tao Zhou <tao.zhou1@amd.com>
Cc: Alex Deucher <Alexander.Deucher@amd.com>
Fixes: c9bdc6c3cf39df ("drm/amdgpu: Add EEPROM I2C address support for ip discovery")
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Fix signedness bug in __amdgpu_eeprom_xfer()

The i2c_transfer() function returns negatives or else the number of
messages transferred. This code does not work because ARRAY_SIZE()
is type size_t and so that means negative values of "r" are type
promoted to high positive values which are greater than the ARRAY_SIZE().

Fix this by changing the < to != which works regardless of type
promotion.

Fixes: 746b584762e452 ("drm/amdgpu: Fixes to the AMDGPU EEPROM driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Optimize EEPROM RAS table I/O

Split functionality between read and write, which
simplifies the code and exposes areas of
optimization and more or less complexity, and take
advantage of that.

Read and write the table in one go; use a separate
stage to decode or encode the data, as opposed to
on the fly, which keeps the I2C bus busy. Use a
single read/write to read/write the table or at
most two if the number of records we're
reading/writing wraps around.

Check the check-sum of a table in EEPROM on init.

Update the checksum at the same time as when
updating the table header signature, when the
threshold was increased on boot.

Take advantage of arithmetic modulo 256, that is,
use a byte!, to greatly simplify checksum
arithmetic.

Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Return result fix in RAS

The low level EEPROM write method, doesn't return
1, but the number of bytes written. Thus do not
compare to 1, instead, compare to greater than 0
for success.

Other cleanup: if the lower layers returned
-errno, then return that, as opposed to
overwriting the error code with one-fits-all
-EINVAL. For instance, some return -EAGAIN.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: I2C EEPROM full memory addressing

* "eeprom_addr" is now 32-bit wide.
* Remove "slave_addr" from the I2C EEPROM driver
interface. The I2C EEPROM Device Type Identifier
is fixed at 1010b, and the rest of the bits
of the Device Address Byte/Device Select Code,
are memory address bits, where the first three
of those bits are the hardware selection bits.
All this is now a 19-bit address and passed
as "eeprom_addr". This abstracts the I2C bus
for EEPROM devices for this I2C EEPROM driver.
Now clients only pass the 19-bit EEPROM memory
address, to the I2C EEPROM driver, as the 32-bit
"eeprom_addr", from which they want to read from
or write to.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: EEPROM respects I2C quirks

Consult the i2c_adapter.quirks table for
the maximum read/write data length per bus
transaction. Do not exceed this transaction
limit.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Fixes to the AMDGPU EEPROM driver

* When reading from the EEPROM device, there is no
device limitation on the number of bytes
read--they're simply sequenced out. Thus, read
the whole data requested in one go.

* When writing to the EEPROM device, there is a
256-byte page limit to write to before having to
generate a STOP on the bus, as well as the
address written to mustn't cross over the page
boundary (it actually rolls over). Maximize the
data written to per bus acquisition.

* Return the number of bytes read/written, or -errno.

* Add kernel doc.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Fix Vega20 I2C to be agnostic (v2)

Teach Vega20 I2C to be agnostic. Allow addressing
different devices while the master holds the bus.
Set STOP as per the controller's specification.

v2: Qualify generating ReSTART before the 1st byte
of the message, when set by the caller, as
those functions are separated, as caught by
Andrey G.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amdgpu: Remember to wait 10ms for write buffer flush v2

EEPROM spec requests this.

v2: Only to be done for write data transactions.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>

drm/amdgpu: add new helper for handling EEPROM i2c transfers

Encapsulates the i2c protocol handling so other parts of the
driver can just tell it the offset and size of data to write.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>