Re: [RFC PATCH v2 09/12] spi: cadence-quadspi: add PHY tuning infrastructure

[Miquel Raynal]

On 07/02/2026 at 00:55:49 +0530, Santhosh Kumar K <s-k6@xxxxxx> wrote:

> On 05/02/26 23:09, Miquel Raynal wrote:
>> On 13/01/2026 at 19:46:14 +0530, Santhosh Kumar K <s-k6@xxxxxx> wrote:
>> 
>>> Implement the spi_controller_mem_ops execute_tuning callback to enable
>>> PHY tuning support for the Cadence controller. PHY tuning optimizes data
>>> capture timing at high frequencies by calibrating the read data capture
>>> delay through the controller's PHY interface.
>>>
>>> Tuning algorithm functions (cqspi_phy_tuning_ddr/sdr and
>>> cqspi_phy_pre/post_config) are placeholders to be implemented
>>> in subsequent commits.
>>>
>>> Signed-off-by: Santhosh Kumar K <s-k6@xxxxxx>
>>> ---
>>>   drivers/spi/spi-cadence-quadspi.c | 241 ++++++++++++++++++++++++++++++
>>>   1 file changed, 241 insertions(+)
>>>
>>> diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
>>> index 0df286d24256..b8b0e85f4f68 100644
>>> --- a/drivers/spi/spi-cadence-quadspi.c
>>> +++ b/drivers/spi/spi-cadence-quadspi.c
>>> @@ -32,6 +32,7 @@
>>>     #define CQSPI_NAME			"cadence-qspi"
>>>   #define CQSPI_MAX_CHIPSELECT		4
>>> +#define CQSPI_AM654_NON_PHY_CLK_RATE	25000000
>>>     static_assert(CQSPI_MAX_CHIPSELECT <= SPI_DEVICE_CS_CNT_MAX);
>>>   @@ -65,6 +66,7 @@ struct cqspi_st;
>>>   struct cqspi_flash_pdata {
>>>   	struct cqspi_st	*cqspi;
>>>   	u32		clk_rate;
>>> +	u32		non_phy_clk_rate;
>> This is the second (and last) main issue I have with the series as it
>> is
>> right now. We cannot set this type of frequency in the driver IMO, it is
>> too board specific.
>> We currently have a DT property for the SPI maximum supported
>> frequency. I believe this is no longer enough. Why not making this
>> frequency property an array? First frequency would be the default,
>> non tuned maximum frequency. The second would be the maximum frequency
>> reachable when tuning the PHY.
>
> If the concern is only about where this is set, we could introduce a DT
> property such as "non-phy-max-freq" to carry this information. This
> would allow us to avoid any changes to the existing "spi-max-frequency"
> handling. Let me know your thoughts on this.

Naming is difficult, non-phy-max-freq is too TI specific. I was
proposing the evolution of spi-max-frequency because it is backward
compatible. The naming can be discussed after you send a proposal, but
do not include "non-phy" in it. It shall reflect the fact that with fine
tuning we can reach higher frequencies on certain operations.

Mark, any take on this?

> I'll also test the approach you suggested and share my inputs based on
> the results. By the way, where are you insisting to adjust/switch to
> the maximum frequency - within the controller driver or in the
> spi-core?

It is preferable to make the decisions in the core and avoid being smart
in controller drivers, if possible.

Thanks,
Miquèl