spi: img-spfi: check for max speed supported by the spfi block

Maximum speed supported by spfi is limited to 1/4 of the spfi clock.

But in some SoCs the maximum speed supported by the spfi block can
be limited to less than 1/4 of the spfi clock. In such cases we have
to define the limit in the device tree so that the driver can pick
it up.

Signed-off-by: Sifan Naeem <sifan.naeem@imgtec.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/spi/spi-img-spfi.c b/drivers/spi/spi-img-spfi.c
index 788e2b176a4f..f31d792a4662 100644
--- a/drivers/spi/spi-img-spfi.c
+++ b/drivers/spi/spi-img-spfi.c
@@ -546,6 +546,7 @@ static int img_spfi_probe(struct platform_device *pdev)
         struct img_spfi *spfi;
         struct resource *res;
         int ret;
+        u32 max_speed_hz;
 
         master = spi_alloc_master(&pdev->dev, sizeof(*spfi));
         if (!master)
@@ -610,6 +611,19 @@ static int img_spfi_probe(struct platform_device *pdev)
         master->max_speed_hz = clk_get_rate(spfi->spfi_clk) / 4;
         master->min_speed_hz = clk_get_rate(spfi->spfi_clk) / 512;
 
+        /*
+         * Maximum speed supported by spfi is limited to the lower value
+         * between 1/4 of the SPFI clock or to "spfi-max-frequency"
+         * defined in the device tree.
+         * If no value is defined in the device tree assume the maximum
+         * speed supported to be 1/4 of the SPFI clock.
+         */
+        if (!of_property_read_u32(spfi->dev->of_node, "spfi-max-frequency",
+                                  &max_speed_hz)) {
+                if (master->max_speed_hz > max_speed_hz)
+                        master->max_speed_hz = max_speed_hz;
+        }
+
         master->setup = img_spfi_setup;
         master->cleanup = img_spfi_cleanup;
         master->transfer_one = img_spfi_transfer_one;