spi: Reintroduce spi_set_cs_timing()

commit 4ccf359849ce ("spi: remove spi_set_cs_timing()"), removed the
method as noboby used it. Nobody used it probably because some SPI
controllers use some default large cs-setup time that covers the usual
cs-setup time required by the spi devices. There are though SPI controllers
that have a smaller granularity for the cs-setup time and their default
value can't fulfill the spi device requirements. That's the case for the
at91 QSPI IPs where the default cs-setup time is half of the QSPI clock
period. This was observed when using an sst26vf064b SPI NOR flash which
needs a spi-cs-setup-ns = <7>; in order to be operated close to its maximum
104 MHz frequency.

Call spi_set_cs_timing() in spi_setup() just before calling spi_set_cs(),
as the latter needs the CS timings already set.
If spi->controller->set_cs_timing is not set, the method will return 0.
There's no functional impact expected for the existing drivers. Even if the
spi-mt65xx.c and spi-tegra114.c drivers set the set_cs_timing method,
there's no user for them as of now. The only tested user of this support
will be a SPI NOR flash that comunicates with the Atmel QSPI controller for
which the support follows in the next patches.

One will notice that this support is a bit different from the one that was
removed in commit 4ccf359849ce ("spi: remove spi_set_cs_timing()"),
because this patch adapts to the changes done after the removal: the move
of the cs delays to the spi device, the retirement of the lelgacy GPIO
handling. The mutex handling was removed from spi_set_cs_timing() because
we now always call spi_set_cs_timing() in spi_setup(), which already
handles the spi->controller->io_mutex, so use the mutex handling from
spi_setup().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20221117105249.115649-4-tudor.ambarus@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b93a608..3cc7bb4 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3622,6 +3622,37 @@ static int __spi_validate_bits_per_word(struct spi_controller *ctlr,
 }
 
 /**
+ * spi_set_cs_timing - configure CS setup, hold, and inactive delays
+ * @spi: the device that requires specific CS timing configuration
+ *
+ * Return: zero on success, else a negative error code.
+ */
+static int spi_set_cs_timing(struct spi_device *spi)
+{
+       struct device *parent = spi->controller->dev.parent;
+       int status = 0;
+
+       if (spi->controller->set_cs_timing && !spi->cs_gpiod) {
+               if (spi->controller->auto_runtime_pm) {
+                       status = pm_runtime_get_sync(parent);
+                       if (status < 0) {
+                               pm_runtime_put_noidle(parent);
+                               dev_err(&spi->controller->dev, "Failed to power device: %d\n",
+                                       status);
+                               return status;
+                       }
+
+                       status = spi->controller->set_cs_timing(spi);
+                       pm_runtime_mark_last_busy(parent);
+                       pm_runtime_put_autosuspend(parent);
+               } else {
+                       status = spi->controller->set_cs_timing(spi);
+               }
+       }
+       return status;
+}
+
+/**
  * spi_setup - setup SPI mode and clock rate
  * @spi: the device whose settings are being modified
  * Context: can sleep, and no requests are queued to the device
@@ -3717,6 +3748,12 @@ int spi_setup(struct spi_device *spi)
                }
        }
 
+       status = spi_set_cs_timing(spi);
+       if (status) {
+               mutex_unlock(&spi->controller->io_mutex);
+               return status;
+       }
+
        if (spi->controller->auto_runtime_pm && spi->controller->set_cs) {
                status = pm_runtime_resume_and_get(spi->controller->dev.parent);
                if (status < 0) {