Hi Felipe,
On Thursday 18 July 2013 04:54 PM, Felipe Balbi wrote:
On Thu, Jul 18, 2013 at 04:48:41PM +0530, Sourav Poddar wrote:
+static void qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+{
+ const u8 *txbuf;
+ int wlen, count;
+
+ count = t->len;
+ txbuf = t->tx_buf;
+ wlen = t->bits_per_word;
+
+ while (count--) {
+ dev_dbg(qspi->dev, "tx cmd %08x dc %08x data %02x\n",
+ qspi->cmd | QSPI_WR_SNGL, qspi->dc, *txbuf);
+ ti_qspi_writel_data(qspi, *txbuf++, QSPI_SPI_DATA_REG, wlen);
you always increment by each byte. Here, if you used writel(), you wrote
4 bytes and should increment txbuf by 4.
hmm..got this point. Yes, my mistake, here I agree if wlen is not 8 bits
txbuf++ is not valid.
Same goes for read_data(),
below. Another thing. Even though your wlen might be 8 bits, if you
write 4 bytes to write, you can save a few CPU cycles by using writel().
Do you mean 4 words of 8 bits?
yeah. Say you have wlen = 8 but the transfer length is 8 bytes (64
bits). If you use writeb(), you will do 8 writes, if you use writel()
you'll do 2 writes.
Just some more findings on this, after wlen bits are transferred we need
an WC interrupt.
So, if I try to pack 4 words of 8bits and use readl/writel, there will
be an interrupt after every
wlen bits transferred and things will get screwd up.
So, for 8 bits word we need to use readb, for 16 bits word readw.
+static int ti_qspi_start_transfer_one(struct spi_master *master,
+ struct spi_message *m)
+{
+ struct ti_qspi *qspi = spi_master_get_devdata(master);
+ struct spi_device *spi = m->spi;
+ struct spi_transfer *t;
+ int status = 0, ret;
+ int frame_length;
+
+ /* setup device control reg */
+ qspi->dc = 0;
+
+ if (spi->mode& SPI_CPHA)
+ qspi->dc |= QSPI_CKPHA(spi->chip_select);
+ if (spi->mode& SPI_CPOL)
+ qspi->dc |= QSPI_CKPOL(spi->chip_select);
+ if (spi->mode& SPI_CS_HIGH)
+ qspi->dc |= QSPI_CSPOL(spi->chip_select);
+
+ frame_length = DIV_ROUND_UP(m->frame_length * spi->bits_per_word,
+ spi->bits_per_word);
this calculation doesn't look correct.
(m->frame_length * spi->bits_per_word) /
spi->bits_per_word = m->frame_length
What are you trying to achieve here ? frame_length should be counted in
words right ? And we get that value in bytes. So what's the best
calculation to convert bytes into words ? If you have 8 bits_per_word
you don't need any calculation, but if you have 32 bits_per_word, you
_do_ need something.
Yes, just derive this formulae with 8 bits per word in mind.
Will change.
It should be (m->frame_length * 8) / spi->bits_per_word
right on. To make sure this will execute a little faster (you never know
what several different versions of GCC will do), instead of multiplying
by 8, left shift by 3.
How will you achieve the number you want ? (hint: 1 byte == 8 bits)
And btw, all of these mistakes pretty much tell me that this driver
hasn't been tested. How have you tested this driver ?
After bootup, I checked for deive detting enumerated as /proc/mtd.
After which I am using mtdutils(erase, dump and write utilied to
check for the communication with the flash device.)
alright, make that clear in your commit log.
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