The patch checks whether the Quad Enable bit is already set in the Status
Register. If so, the function exits immediately with a successful return
code.
Signed-off-by: Cyrille Pitchen <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>
---
drivers/mtd/spi-nor/spi-nor.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index da7cd69d4857..1fd32b991eb7 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1216,6 +1216,9 @@ static int macronix_quad_enable(struct spi_nor *nor)
val = read_sr(nor);
if (val < 0)
return val;
+ if (val & SR_QUAD_EN_MX)
+ return 0;
+
write_enable(nor);
write_sr(nor, val | SR_QUAD_EN_MX);
--
2.7.4
On 12/06/2016 05:01 PM, Cyrille Pitchen wrote:
> The patch checks whether the Quad Enable bit is already set in the Status
> Register. If so, the function exits immediately with a successful return
> code.
Performance optimization I presume ?
Acked-by: Marek Vasut <[email protected]>
> Signed-off-by: Cyrille Pitchen <[email protected]>
> Reviewed-by: Jagan Teki <[email protected]>
> ---
> drivers/mtd/spi-nor/spi-nor.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index da7cd69d4857..1fd32b991eb7 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -1216,6 +1216,9 @@ static int macronix_quad_enable(struct spi_nor *nor)
> val = read_sr(nor);
> if (val < 0)
> return val;
> + if (val & SR_QUAD_EN_MX)
> + return 0;
> +
> write_enable(nor);
>
> write_sr(nor, val | SR_QUAD_EN_MX);
>
--
Best regards,
Marek Vasut
Le 06/12/2016 ? 20:01, Marek Vasut a ?crit :
> On 12/06/2016 05:01 PM, Cyrille Pitchen wrote:
>> The patch checks whether the Quad Enable bit is already set in the Status
>> Register. If so, the function exits immediately with a successful return
>> code.
>
> Performance optimization I presume ?
Performance optimization is one benefit but this real purpose of the
patch is to avoid writing over and over a non-volatile bit at each boot,
actually each time spi_nor_scan() is called.
To be honest, I don't know whether internally the SPI memory is clever
enough not to perform the actual write when it sees the bit value has
not changed. I wanted to improve the memory lifetime by avoiding the
update of the bit from software just to be sure :)
Anyway, thanks for your review!
>
> Acked-by: Marek Vasut <[email protected]>
>
>> Signed-off-by: Cyrille Pitchen <[email protected]>
>> Reviewed-by: Jagan Teki <[email protected]>
>> ---
>> drivers/mtd/spi-nor/spi-nor.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index da7cd69d4857..1fd32b991eb7 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -1216,6 +1216,9 @@ static int macronix_quad_enable(struct spi_nor *nor)
>> val = read_sr(nor);
>> if (val < 0)
>> return val;
>> + if (val & SR_QUAD_EN_MX)
>> + return 0;
>> +
>> write_enable(nor);
>>
>> write_sr(nor, val | SR_QUAD_EN_MX);
>>
>
>
On 12/07/2016 12:05 AM, Cyrille Pitchen wrote:
> Le 06/12/2016 ? 20:01, Marek Vasut a ?crit :
>> On 12/06/2016 05:01 PM, Cyrille Pitchen wrote:
>>> The patch checks whether the Quad Enable bit is already set in the Status
>>> Register. If so, the function exits immediately with a successful return
>>> code.
>>
>> Performance optimization I presume ?
>
> Performance optimization is one benefit but this real purpose of the
> patch is to avoid writing over and over a non-volatile bit at each boot,
> actually each time spi_nor_scan() is called.
>
> To be honest, I don't know whether internally the SPI memory is clever
> enough not to perform the actual write when it sees the bit value has
> not changed. I wanted to improve the memory lifetime by avoiding the
> update of the bit from software just to be sure :)
Well the bit is in some sort of internal SRAM or silicon register , no?
> Anyway, thanks for your review!
np
>> Acked-by: Marek Vasut <[email protected]>
>>
>>> Signed-off-by: Cyrille Pitchen <[email protected]>
>>> Reviewed-by: Jagan Teki <[email protected]>
>>> ---
>>> drivers/mtd/spi-nor/spi-nor.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>>> index da7cd69d4857..1fd32b991eb7 100644
>>> --- a/drivers/mtd/spi-nor/spi-nor.c
>>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>>> @@ -1216,6 +1216,9 @@ static int macronix_quad_enable(struct spi_nor *nor)
>>> val = read_sr(nor);
>>> if (val < 0)
>>> return val;
>>> + if (val & SR_QUAD_EN_MX)
>>> + return 0;
>>> +
>>> write_enable(nor);
>>>
>>> write_sr(nor, val | SR_QUAD_EN_MX);
>>>
>>
>>
>
--
Best regards,
Marek Vasut
Le 06/12/2016 ? 20:01, Marek Vasut a ?crit :
> On 12/06/2016 05:01 PM, Cyrille Pitchen wrote:
>> The patch checks whether the Quad Enable bit is already set in the Status
>> Register. If so, the function exits immediately with a successful return
>> code.
>
> Performance optimization I presume ?
>
> Acked-by: Marek Vasut <[email protected]>
>
>> Signed-off-by: Cyrille Pitchen <[email protected]>
>> Reviewed-by: Jagan Teki <[email protected]>
Applied to git://github.com/spi-nor/linux.git
>> ---
>> drivers/mtd/spi-nor/spi-nor.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index da7cd69d4857..1fd32b991eb7 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -1216,6 +1216,9 @@ static int macronix_quad_enable(struct spi_nor *nor)
>> val = read_sr(nor);
>> if (val < 0)
>> return val;
>> + if (val & SR_QUAD_EN_MX)
>> + return 0;
>> +
>> write_enable(nor);
>>
>> write_sr(nor, val | SR_QUAD_EN_MX);
>>
>
>