[PATCH linux 2/3] mtd: spi-nor: aspeed: add support for SPI dual IO read mode

[Cédric Le Goater]

On 01/10/2017 11:54 PM, Rob Lippert wrote:
> On Tue, Jan 10, 2017 at 12:10 AM, Cédric Le Goater <clg at kaod.org> wrote:
>>
>> Hello Robert,
>>
>> On 01/10/2017 02:05 AM, Robert Lippert wrote:
>>> Implements support for the dual IO read mode on aspeed SMC/FMC
>>> controllers which uses both MISO and MOSI lines for data during a read
>>> to double the read bandwidth.
>>>
>>> Signed-off-by: Robert Lippert <rlippert at google.com>
>>> ---
>>>
>>>  drivers/mtd/spi-nor/aspeed-smc.c | 28 ++++++++++++++++++++++------
>>>  1 file changed, 22 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/aspeed-smc.c b/drivers/mtd/spi-nor/aspeed-smc.c
>>> index d3bed34f5aa0..a8ca2ab308d7 100644
>>> --- a/drivers/mtd/spi-nor/aspeed-smc.c
>>> +++ b/drivers/mtd/spi-nor/aspeed-smc.c
>>> @@ -540,6 +540,9 @@ static int aspeed_smc_read_user(struct spi_nor *nor, loff_t from, size_t len,
>>>  {
>>>       struct aspeed_smc_chip *chip = nor->priv;
>>>       int ret;
>>> +     u32 ctl;
>>> +     int i;
>>> +     u8 dummy = 0;
>>
>> OxFF would be a better value.
> 
> OK.
> 
>>
>>>       mutex_lock(&chip->controller->mutex);
>>>
>>> @@ -557,6 +560,18 @@ static int aspeed_smc_read_user(struct spi_nor *nor, loff_t from, size_t len,
>>>
>>>       aspeed_smc_start_user(nor);
>>>       aspeed_smc_send_cmd_addr(nor, nor->read_opcode, from);
>>> +
>>> +     /* Send dummy bytes */
>>> +     for (i = 0; i < (chip->nor.read_dummy / 8); ++i)
>>
>> the parentheses are not needed I think.
> 
> Yes not needed, removed.
> 
>>
>>> +             aspeed_smc_write_to_ahb(chip->base, &dummy, 1);
>>> +
>>> +     if (chip->nor.flash_read == SPI_NOR_DUAL) {
>>> +             /* Switch to dual I/O mode for data cycle */
>>> +             ctl = readl(chip->ctl) & ~CONTROL_SPI_IO_MODE_MASK;
>>> +             ctl |= CONTROL_SPI_IO_DUAL_DATA;
>>> +             writel(ctl, chip->ctl);
>>> +     }
>>
>> So why can not we set the controller in aspeed_smc_chip_setup_finish()
>> once and for all ?
> 
> It needs to make sure to only effect the data part of the operation
> (the command+addr writes to the device should not be dual-IO mode),
> and also needs to not interfere with the aspeed_smc_read_reg read
> calls in which the data phase cannot be dual IO mode.

ok. it makes sense. Is it much faster ? 

Thanks, 

C.

>>
>>> +
>>>       aspeed_smc_read_from_ahb(read_buf, chip->base, len);
>>>       aspeed_smc_stop_user(nor);
>>>
>>> @@ -868,6 +883,7 @@ static int aspeed_smc_chip_setup_finish(struct aspeed_smc_chip *chip)
>>>               cmd = CONTROL_SPI_COMMAND_MODE_NORMAL;
>>>               break;
>>>       case SPI_NOR_FAST:
>>> +     case SPI_NOR_DUAL:
>>>               cmd = CONTROL_SPI_COMMAND_MODE_FREAD;
>>>               break;
>>>       default:
>>> @@ -876,9 +892,13 @@ static int aspeed_smc_chip_setup_finish(struct aspeed_smc_chip *chip)
>>>       }
>>>
>>>       chip->ctl_val[smc_read] |= cmd |
>>> +             spi_control_fill_opcode(chip->nor.read_opcode) |
>>>               CONTROL_SPI_IO_DUMMY_CYCLES_SET(chip->nor.read_dummy / 8);
>>>
>>> -     dev_dbg(controller->dev, "base control register: %08x\n",
>>> +     if (chip->nor.flash_read == SPI_NOR_DUAL)
>>> +             chip->ctl_val[smc_read] |= CONTROL_SPI_IO_DUAL_DATA;
>>
>> may be we can move that part in the switch setting above  ?
> 
> Done.
> 
>>
>>> +     dev_info(controller->dev, "read control register: %08x\n",
>>>                chip->ctl_val[smc_read]);
>>
>> may be keep dev_dbg, but the change of 'base' by 'read' is ok.
> 
> OK.
> 
>>
>> Thanks,
>>
>> C.
>>
>>>       return 0;
>>>  }
>>> @@ -980,11 +1000,7 @@ static int aspeed_smc_probe(struct platform_device *pdev)
>>>               if (err)
>>>                       continue;
>>>
>>> -             /*
>>> -              * XXX Add support for SPI_NOR_QUAD and SPI_NOR_DUAL attach
>>> -              * when board support is present as determined by of property.
>>> -              */
>>> -             err = spi_nor_scan(&chip->nor, NULL, SPI_NOR_NORMAL);
>>> +             err = spi_nor_scan(&chip->nor, NULL, SPI_NOR_DUAL);
>>>               if (err)
>>>                       continue;
>>>
>>>
>>