[PATCH 4/4] mtd: spi-nor: aspeed: use command mode for reads

[Cédric Le Goater]

On 04/20/2017 03:31 PM, Marek Vasut wrote:
> On 04/20/2017 01:56 PM, Cédric Le Goater wrote:
>> When reading flash contents, try to use the "command mode" if the AHB
>> window configured for the flash module is big enough. Else, just fall
>> back to the "user mode" to perform the read.
>>
>> Signed-off-by: Cédric Le Goater <clg at kaod.org>
>> ---
>>
>>  Changes since initial version :
>>
>>  - rebased on current patchset which removed DMA support
>>
>>  drivers/mtd/spi-nor/aspeed-smc.c | 27 ++++++++++++++++++++++++++-
>>  1 file changed, 26 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/spi-nor/aspeed-smc.c b/drivers/mtd/spi-nor/aspeed-smc.c
>> index 60c020482946..43015aec4557 100644
>> --- a/drivers/mtd/spi-nor/aspeed-smc.c
>> +++ b/drivers/mtd/spi-nor/aspeed-smc.c
>> @@ -394,6 +394,31 @@ static ssize_t aspeed_smc_read_user(struct spi_nor *nor, loff_t from,
>>  
>>  	aspeed_smc_read_from_ahb(read_buf, chip->ahb_base, len);
>>  	aspeed_smc_stop_user(nor);
>> +	return 0;
>> +}
>> +
>> +static ssize_t aspeed_smc_read(struct spi_nor *nor, loff_t from, size_t len,
>> +			       u_char *read_buf)
>> +{
>> +	struct aspeed_smc_chip *chip = nor->priv;
>> +
>> +	/*
>> +	 * The AHB window configured for the chip is too small for the
>> +	 * read offset. Use the "User mode" of the controller to
>> +	 * perform the read.
>> +	 */
>> +	if (from >= chip->ahb_window_size) {
>> +		aspeed_smc_read_user(nor, from, len, read_buf);
>> +		goto out;
> 
> What about turning this into dumb if () {} else {} and dropping the goto ?

yes, well, this is because I have other patches adding DMAs :

	https://github.com/legoater/linux/commit/6880924dc2cf7a47c446a708df528b72d9bf9134#diff-e466368d609006970aab53a7b840221fR575

but as of today, the benefits in speed are to be proven and the current 
implementation does not support vmalloc'ed buffers. So I can drop the 
goto without too much regrets (if you insist :)

Cheers,

C.  
 
>> +	}
>> +
>> +	/*
>> +	 * Use the "Command mode" to do a direct read from the AHB
>> +	 * window configured for the chip. This should be the default.
>> +	 */
>> +	memcpy_fromio(read_buf, chip->ahb_base + from, len);
>> +
>> +out:
>>  	return len;
>>  }
>>  
>> @@ -817,7 +842,7 @@ static int aspeed_smc_setup_flash(struct aspeed_smc_controller *controller,
>>  		nor->dev = dev;
>>  		nor->priv = chip;
>>  		spi_nor_set_flash_node(nor, child);
>> -		nor->read = aspeed_smc_read_user;
>> +		nor->read = aspeed_smc_read;
>>  		nor->write = aspeed_smc_write_user;
>>  		nor->read_reg = aspeed_smc_read_reg;
>>  		nor->write_reg = aspeed_smc_write_reg;
>>
> 
>