[PATCH v2] spi: img-spfi: check for max speed supported by the spfi block

From: Sifan Naeem
Date: Thu Jun 18 2015 - 08:25:42 EST


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@xxxxxxxxxx>
---
changes from v1: coding style fix.
.../devicetree/bindings/spi/spi-img-spfi.txt | 1 +
drivers/spi/spi-img-spfi.c | 14 ++++++++++++++
2 files changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/spi/spi-img-spfi.txt b/Documentation/devicetree/bindings/spi/spi-img-spfi.txt
index e02fbf1..494db60 100644
--- a/Documentation/devicetree/bindings/spi/spi-img-spfi.txt
+++ b/Documentation/devicetree/bindings/spi/spi-img-spfi.txt
@@ -21,6 +21,7 @@ Required properties:
Optional properties:
- img,supports-quad-mode: Should be set if the interface supports quad mode
SPI transfers.
+- spfi-max-frequency: Maximum speed supported by the spfi block.

Example:

diff --git a/drivers/spi/spi-img-spfi.c b/drivers/spi/spi-img-spfi.c
index acce90a..00f1ac3 100644
--- a/drivers/spi/spi-img-spfi.c
+++ b/drivers/spi/spi-img-spfi.c
@@ -548,6 +548,7 @@ 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)
@@ -612,6 +613,19 @@ 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;
--
1.7.9.5

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