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

[Marek Vasut <marek.vasut@gmail.com>]

On 04/20/2017 03:53 PM, Cédric Le Goater wrote:
> 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@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 :)

Nah, if you have further plans with this code, I don't mind either way.

-- 
Best regards,
Marek Vasut