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How can I modify the mux during runtime?

Question asked by Jose Argao on Jul 11, 2018
Latest reply on Jul 31, 2018 by gusarambula

I am working with a custom imx6dlsabresd board and I want to dynamically change the clk line to a GPIO and then back again as needed. By default the pin is muxed as an SPI clk on the dtb and controlled by the spi-imx.c driver. I modified this driver to write to the IOMUXC register and change the clk pin to a GPIO, then I requested this GPIO and did some test value modifications. All of the operations reported success but the changes were not being reflected on the line. Here is the code I tried as a proof of concept:


static void spi_imx_clk_debug(void)


       void __iomem *clkmux = ioremap(0x020E0144, 4);

       uint32_t spimux= ioread32(clkmux);

       printk("[SPI] IOMUXC Before DEBUG: 0x%08X\n", spimux);


       uint32_t gpiomux = spimux & 0xFFFFFFF0;

       gpiomux |= 0x5;

       iowrite32(gpiomux, clkmux);


       printk("[SPI] IOMUXC DURING DEBUG: 0x%08X\n", ioread32(clkmux));


       iowrite32(spimux, clkmux);


       int ret = gpio_request(80, "spi_clk_gpio");

       printk("[SPI] gpio_request: %d\n", ret);

       ret = gpio_direction_output(80, 0);

       printk("[SPI] gpio_direction_output: %d\n", ret);


       gpio_set_value(80, 1);


       gpio_set_value(80, 0);


       gpio_set_value(80, 1);


       gpio_set_value(80, 0);




       printk("[SPI] IOMUXC AFTER DEBUG: 0x%08X\n", ioread32(clkmux));




I called this function within the spi_imx_prepare_message function and it seemed to be executed successfully, but I could not see any changes on the clk line. Am I missing something here?