[PATCH] mtd: revert "spi-nor: intel: provide a range for poll_timout"

[Tudor.Ambarus at microchip.com]

Hi, Alexander,

On 7/22/20 7:37 PM, Alexander Sverdlin wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Hello Luis,
> 
> thank you for the patch!
> 
> On 11/06/2020 00:46, Luis Alberto Herrera wrote:
>> This change reverts aba3a882a178: "mtd: spi-nor: intel: provide a range
>> for poll_timout". That change introduces a performance regression when
>> reading sequentially from flash. Logging calls to intel_spi_read without
>> this change we get:
>>
>> Start MTD read
>> [   20.045527] intel_spi_read(from=1800000, len=400000)
>> [   20.045527] intel_spi_read(from=1800000, len=400000)
>> [  282.199274] intel_spi_read(from=1c00000, len=400000)
>> [  282.199274] intel_spi_read(from=1c00000, len=400000)
>> [  544.351528] intel_spi_read(from=2000000, len=400000)
>> [  544.351528] intel_spi_read(from=2000000, len=400000)
>> End MTD read
>>
>> With this change:
>>
>> Start MTD read
>> [   21.942922] intel_spi_read(from=1c00000, len=400000)
>> [   21.942922] intel_spi_read(from=1c00000, len=400000)
>> [   23.784058] intel_spi_read(from=2000000, len=400000)
>> [   23.784058] intel_spi_read(from=2000000, len=400000)
>> [   25.625006] intel_spi_read(from=2400000, len=400000)
>> [   25.625006] intel_spi_read(from=2400000, len=400000)
>> End MTD read
> 
> I've performed my testing as well and got the following results:
> 
> Vanilla Linux 4.9 (i.e. before the introduction of the offending
> patch):
> 
> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k
> 1280+0 records in
> 1280+0 records out
> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 3.91981 s, 1.3 MB/s
> 
> Vanilla 4.19 (i.e. with offending patch):
> 
> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k
> 1280+0 records in
> 1280+0 records out
> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 6.70891 s, 781 kB/s
> 
> 4.19 + revert:
> 
> dd if=/dev/flash/by-name/XXX of=/dev/null bs=4k
> 1280+0 records in
> 1280+0 records out
> 5242880 bytes (5.2 MB, 5.0 MiB) copied, 3.90503 s, 1.3 MB/s
> 
> Therefore it looks good from my PoV:
> 
> Tested-by: Alexander Sverdlin <alexander.sverdlin at gmail.com>
> 
>> Signed-off-by: Luis Alberto Herrera <luisalberto at google.com>
>> Acked-by: Mika Westerberg <mika.westerberg at linux.intel.com>
>> ---
>>  drivers/mtd/spi-nor/controllers/intel-spi.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/controllers/intel-spi.c b/drivers/mtd/spi-nor/controllers/intel-spi.c
>> index 61d2a0ad2131..2b89361a0d3a 100644
>> --- a/drivers/mtd/spi-nor/controllers/intel-spi.c
>> +++ b/drivers/mtd/spi-nor/controllers/intel-spi.c
>> @@ -292,7 +292,7 @@ static int intel_spi_wait_hw_busy(struct intel_spi *ispi)
>>       u32 val;
>>
>>       return readl_poll_timeout(ispi->base + HSFSTS_CTL, val,
>> -                               !(val & HSFSTS_CTL_SCIP), 40,>> +                               !(val & HSFSTS_CTL_SCIP), 0,

would you put 10 us here
>>                                 INTEL_SPI_TIMEOUT * 1000);
>>  }
>>
>> @@ -301,7 +301,7 @@ static int intel_spi_wait_sw_busy(struct intel_spi *ispi)
>>       u32 val;
>>
>>       return readl_poll_timeout(ispi->sregs + SSFSTS_CTL, val,
>> -                               !(val & SSFSTS_CTL_SCIP), 40,
>> +                               !(val & SSFSTS_CTL_SCIP), 0,

also here, and re-do a test? I'm curios if the performance will be
as it was before.

Thanks!

>>                                 INTEL_SPI_TIMEOUT * 1000);
>>  }
>>
>>
> 
> --
> Best regards,
> Alexander Sverdlin.
>