Re: [PATCH v3 01/13] spi: atmel-quadspi: cache MR value to avoid a write access

Tudor.Ambarus
2019-02-02T08:39:12Z

On 02/02/2019 09:06 AM, Boris Brezillon wrote:
> On Sat, 2 Feb 2019 04:07:13 +0000
> <Tudor.Ambarus@microchip.com> wrote:
>
>> From: Tudor Ambarus <tudor.ambarus@microchip.com>
>>
>> Cache Serial Memory Mode (SMM) value to avoid write access when
>> setting the controller in serial memory mode. SMM is set in
>> exec_op() and not at probe time, to let room for future regular
>> SPI support.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
>> ---
>> v3: update smm value when different. rename mr/smm
>> v2: cache MR value instead of moving the write access at probe
>>
>> drivers/spi/atmel-quadspi.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
>> index ddc712410812..645284c6ec9a 100644
>> --- a/drivers/spi/atmel-quadspi.c
>> +++ b/drivers/spi/atmel-quadspi.c
>> @@ -155,6 +155,7 @@ struct atmel_qspi {
>> struct clk *clk;
>> struct platform_device *pdev;
>> u32 pending;
>> + u32 smm;
>> struct completion cmd_completion;
>> };
>>
>> @@ -238,7 +239,11 @@ static int atmel_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
>> icr = QSPI_ICR_INST(op->cmd.opcode);
>> ifr = QSPI_IFR_INSTEN;
>>
>> - qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
>> + /* Set the QSPI controller in Serial Memory Mode */
>> + if (aq->smm != QSPI_MR_SMM) {
>
> Sorry, I think I misunderstood your previous suggestion, I thought the
> reg was called SMM. If the reg is called MR and the value you expect in
> there is SMM, then the field should be named ->mr as it caches the
> whole reg, not only the SMM bit. So it's actually:
>
> if (aq->mr != QSPI_MR_SMM) {

No worries. When keeping the reg name, and not the bit itself, I would expect to
do the check as in v2, to let room for checking other bits too:

+ if (!(aq->mr & QSPI_MR_SMM))

I don't have any problems to keep "mr" name, but I would like to understand your
reasons.

Thanks,
ta

>
>> + qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
>> + aq->smm = QSPI_MR_SMM;
>> + }
>>
>> mode = find_mode(op);
>> if (mode < 0)
>
>
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