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

[Rob Lippert]

On Wed, Jan 11, 2017 at 3:43 AM, Cédric Le Goater <clg at kaod.org> wrote:
> 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 ?

Yea it is about twice as much bandwidth, as I mentioned in the cover
letter it drops the time to dump an entire 64MB flash from 12s to 7s.

With a companion change to u-boot to double the SPI frequency to
104Mhz that time drops to 3s and speeds up the entire bmc boot process
(including uboot) by about 15s.

Thanks,
-Rob

>
> 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;
>>>>
>>>>
>>>
>