Hi,
(2015/03/16 16:50), Geert Uytterhoeven wrote:
Hi Iwamatsu-san,
On Mon, Mar 16, 2015 at 2:18 AM, Nobuhiro Iwamatsu
<nobuhiro.iwamatsu.yj@xxxxxxxxxxx> wrote:
2015-03-12 21:35 GMT+09:00 Geert Uytterhoeven<geert@xxxxxxxxxxxxxx>:
On Thu, Mar 12, 2015 at 3:31 AM, Nobuhiro Iwamatsu
<nobuhiro.iwamatsu.yj@xxxxxxxxxxx> wrote:
- /* limit maximum word transfer to rx/tx fifo size */
- if (tx_buf)
- words = min_t(int, words, p->tx_fifo_size);
- if (rx_buf)
- words = min_t(int, words, p->rx_fifo_size);
Sorry, I fail to see what exactly this is fixing.
If SPI_MASTER_MUST_TX is set, all hardware SPI transfers are either
a) transmit-only.
b) bidirectional (transmit buffer may be a dummy, provided by the SPI core).
For case a, only the TX FIFO size matters.
- The original code ignored the RX FIFO size (rx_buf == NULL),
- After your change, it always uses the minimum of the TX and RX FIFO sizes
(granted, the RX FIFO size is larger, so this doesn't make a difference on
current hardware).
Yes.
For case b, both FIFO sizes matter, and the original code handled that fine
(tx_buf != NULL, rx_buf != NULL).
What am I missing?
Are you using a backport with broken SPI_MASTER_MUST_TX handling in the SPI
core?
When tx_buf != NULL and rx_buf != NULL, current code uses FIFO size of
rx_buffer.
Since TX FIFO size is smaller than RX FIFO size, corrent code set the
wrong value to SITMDR2 register.
if tx_buf != NULL and rx_buf != NULL, current code does:
words = min_t(int, words, p->tx_fifo_size);
words = min_t(int, words, p->rx_fifo_size);
Hence words will be the minimum of the original value of words, tx_fifo_size,
and rx_fifo_size. What's wrong about that?
I see. I understood about this.
Sorry, my bad.
Mark, if you do not apply this patch to your repository, could you ignore this?
Therefore, this patch selects a smaller FIFO size, adds the function to set.
Does this has become a description?
I've just verified that with today's tree (renesas-drivers-2015-03-12-v4.0-rc3),
SPI_MASTER_MUST_TX works fine, and a dummy tx_buf is passed when needed.
I think correctly work on hardware. However, driver has been set to
the correct register value?
I printed the value of words, which is passed to sh_msiof_spi_set_mode_regs().
Gr{oetje,eeting}s,
Geert
Best regards,
Nobuhiro
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