On 7/19/21 10:20 AM, Uwe Kleine-König wrote:
[...]
@@ -505,7 +505,9 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx,
struct spi_message *msg)
{
struct spi_device *spi = msg->spi;
+ struct spi_transfer *xfer;
u32 ctrl = MX51_ECSPI_CTRL_ENABLE;
+ u32 min_speed_hz = ~0U;
u32 testreg, delay;
u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG);
@@ -578,7 +580,13 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx,
* the SPI communication as the device on the other end would consider
* the change of SCLK polarity as a clock tick already.
*/
- delay = (2 * 1000000) / spi_imx->spi_bus_clk;
+ list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+ if (!xfer->speed_hz)
+ continue;
+ min_speed_hz = min(xfer->speed_hz, min_speed_hz);
+ }
Can it happen that all transfer's spped_hz are zero?
I don't think so, what kind of spi_message would that be ?
And even if it was zero, the delay would be 2000000/~0U , so zero as
well, which I suppose is the best we can do in such a case.
+
+ delay = (2 * 1000000) / min_speed_hz;
Orthogonal to your change: I wonder if we need to round up the division
here.
That is not necessary, since the delay here is twice what it needs to be
(because we really do not know what happens in the hardware internally).
if (likely(delay < 10)) /* SCLK is faster than 100 kHz */
udelay(delay);
else /* SCLK is _very_ slow */
Also the comments are wrong here. Is SCLK is 150 kHz we have
min_speed_hz = 150000, right? Then delay becomes 13 and the slow freq
path is entered. The right comment (when keeping delay = (2 * 1000000) /
min_speed_hz) would be
if (likely(delay < 10)) /* SCLK is faster than 181.818 kHz */
This whole if/else is in fact based on
Documentation/timers/timers-howto.rst , which says use usleep_range()
for delays above 10uS or so.
The comment should be updated, but that's a separate patch.
--
Best regards,
Marek Vasut
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-56 Email: marex@xxxxxxx
