Re: [PATCH 1/3] spi/qspi: Add memory mapped read support.

[Sourav Poddar <sourav.poddar@ti.com>]

On Tuesday 15 October 2013 06:16 PM, Mark Brown wrote:
> On Tue, Oct 15, 2013 at 05:19:07PM +0530, Sourav Poddar wrote:
>> On Tuesday 15 October 2013 04:46 PM, Mark Brown wrote:
>>> Can you fix this by enabling the clock is enabled when you return the
>>> buffer to the MTD layer and then disabling the clock when the buffer is
>>> released?
>> Sorry, I did not get you here. With memory mapped read, there is no
>> buffer exchanged, everything takes place at the mtd layer only, what gets
>> exchanged is just the memory mapped address.
> The buffer is the memory mapped address - part of getting the address
> should be preparing the hardware for it.
>
>>       if (spi->mode&&  SPI_RX_MMAP) {
>>           printk("memory mapped mode set\n");
>> -        flash->mmap_read = true;
>> +        flash->mmap_read = spi->memory_map;
> So this probably needs to be a function call to get the buffer (and a
> corresponding one to free it).
So, the flow can be something like this:

drivers/mtd/devices/m25p80.c
get_flash_buf()
{
     lock();

      t[0] = GET_BUFFER;
      t[1] = buf;
      ......

      spi_sync();

     unlock();
}

mtd_read
{
     get_flash_buf();

     if (flash->buf) {
         memcpy();
        return 0;
   }
}

Not sure, if free buf is needed as devm_* variant is used to allocate that
memory.


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