Re: [PATCH v3 2/2] mtd: spi-nor: cadence-quadspi: Add support for Octal SPI controller

[Vignesh R]

On 20/01/19 8:58 PM, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> Vignesh,
> 
> On 01/20/2019 04:56 PM, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
>> Looks good.
> 
> one more thing: in cqspi_read_setup() I see that the dummy cycles are adjusted
> if (f_pdata->inst_width != CQSPI_INST_TYPE_QUAD).
> 
> Should you adjust the dummy cycles for octo too? 

Driver does not claim support for SNOR_HWCAPS_PP_4_4_4 mode or
SNOR_HWCAPS_PP_8_8_8 mode. Therefore inst_width is always be
CQSPI_INST_TYPE_SINGLE (cqspi_set_protocol() always sets inst_width and
addr_width to CQSPI_INST_TYPE_SINGLE).
Code to support 4_4_4 or 8_8_8 mode is incomplete in the driver. Also,
using mode bits to satisfy dummy clk cycles does not seem right. My
guess is driver is broken, if inst_width is indeed CQSPI_INST_TYPE_QUAD
as we end up sending additional 8 dummy clock cycles over what is asked
in nor->read_dummy.
I will plan to fix these as part of moving driver over to spi-mem. But
above code should not impact 1-1-8 mode support.

> I tried to find a datasheet for the controller, without success though ...
> 

You can find Octal SPI controller datasheet in AM65x SoC TRM here:
http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf
Page 9449: 12.3.2 Octal Serial Peripheral Interface (OSPI)



-- 
Regards
Vignesh