Reply to t113的spi设置clk的频率 on Thu, 12 Oct 2023 02:39:39 GMT

axw_fae — Thu, 12 Oct 2023 02:39:39 GMT

你要注意一下，这儿的 spi 速度值并不是可以随便设置的！因為 cpu 除频后会配不上！会跳到默认的 10Mhz 的速度。

建议你可以在 .... spi 中，加打印，看看你那值是否可以通过！

/driver/spi/spi-sunxi.c 中

/* set spi clock */
static void spi_set_clk(u32 spi_clk, u32 ahb_clk, struct sunxi_spi *sspi)
{
        u32 spi_test = 100000000;
        u32 get_spi;

	dprintk(DEBUG_INFO, "set spi clock %d, mclk %d\n", spi_clk, ahb_clk);


	for(spi_test = 50000000; spi_test >= 20000000; spi_test -= 1000000)
	{
		clk_set_rate(sspi->mclk, spi_test);
		get_spi = clk_get_rate(sspi->mclk);
		printk("spi_test %d  == get %d \n", spi_test, get_spi);

        }

像我以 100Mhz 到 80Mhz ，每 1Mhz 做变化！

[    1.079831] spi_test 100000000  == get 100000000 ␍␊
[    1.093426] spi_test 99000000  == get 96000000 ␍␊
[    1.098527] spi_test 98000000  == get 96000000 ␍␊
[    1.103587] spi_test 97000000  == get 96000000 ␍␊
[    1.108714] spi_test 96000000  == get 96000000 ␍␊
[    1.113807] spi_test 95000000  == get 92307692 ␍␊
[    1.118905] spi_test 94000000  == get 92307692 ␍␊
[    1.123996] spi_test 93000000  == get 92307692 ␍␊
[    1.129127] spi_test 92000000  == get 87771428 ␍␊
[    1.134193] spi_test 91000000  == get 87771428 ␍␊
[    1.139293] spi_test 90000000  == get 87771428 ␍␊
[    1.144406] spi_test 89000000  == get 87771428 ␍␊
[    1.149506] spi_test 88000000  == get 87771428 ␍␊
[    1.154601] spi_test 87000000  == get 85714285 ␍␊
[    1.159739] spi_test 86000000  == get 85714285 ␍␊
[    1.164835] spi_test 85000000  == get 80000000 ␍␊
[    1.169939] spi_test 84000000  == get 80000000 ␍␊
[    1.175074] spi_test 83000000  == get 80000000 ␍␊
[    1.180142] spi_test 82000000  == get 80000000 ␍␊
[    1.185243] spi_test 81000000  == get 80000000 ␍␊
[    1.190346] spi_test 80000000  == get 80000000 ␍␊

就可以知道，有一些值设置是不行的！要特定值才行！