diff options
Diffstat (limited to 'arch/powerpc/platforms/512x/mpc512x_shared.c')
| -rw-r--r-- | arch/powerpc/platforms/512x/mpc512x_shared.c | 169 |
1 files changed, 92 insertions, 77 deletions
diff --git a/arch/powerpc/platforms/512x/mpc512x_shared.c b/arch/powerpc/platforms/512x/mpc512x_shared.c index 36b5652aada2..adb95f03d4d4 100644 --- a/arch/powerpc/platforms/512x/mpc512x_shared.c +++ b/arch/powerpc/platforms/512x/mpc512x_shared.c @@ -12,6 +12,7 @@ * (at your option) any later version. */ +#include <linux/clk.h> #include <linux/kernel.h> #include <linux/io.h> #include <linux/irq.h> @@ -68,98 +69,112 @@ struct fsl_diu_shared_fb { bool in_use; }; -#define DIU_DIV_MASK 0x000000ff +/* receives a pixel clock spec in pico seconds, adjusts the DIU clock rate */ static void mpc512x_set_pixel_clock(unsigned int pixclock) { - unsigned long bestval, bestfreq, speed, busfreq; - unsigned long minpixclock, maxpixclock, pixval; - struct mpc512x_ccm __iomem *ccm; struct device_node *np; - u32 temp; - long err; - int i; + struct clk *clk_diu; + unsigned long epsilon, minpixclock, maxpixclock; + unsigned long offset, want, got, delta; - np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-clock"); + /* lookup and enable the DIU clock */ + np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-diu"); if (!np) { - pr_err("Can't find clock control module.\n"); + pr_err("Could not find DIU device tree node.\n"); return; } - - ccm = of_iomap(np, 0); + clk_diu = of_clk_get(np, 0); + if (IS_ERR(clk_diu)) { + /* backwards compat with device trees that lack clock specs */ + clk_diu = clk_get_sys(np->name, "ipg"); + } of_node_put(np); - if (!ccm) { - pr_err("Can't map clock control module reg.\n"); + if (IS_ERR(clk_diu)) { + pr_err("Could not lookup DIU clock.\n"); return; } - - np = of_find_node_by_type(NULL, "cpu"); - if (np) { - const unsigned int *prop = - of_get_property(np, "bus-frequency", NULL); - - of_node_put(np); - if (prop) { - busfreq = *prop; - } else { - pr_err("Can't get bus-frequency property\n"); - return; - } - } else { - pr_err("Can't find 'cpu' node.\n"); + if (clk_prepare_enable(clk_diu)) { + pr_err("Could not enable DIU clock.\n"); return; } - /* Pixel Clock configuration */ - pr_debug("DIU: Bus Frequency = %lu\n", busfreq); - speed = busfreq * 4; /* DIU_DIV ratio is 4 * CSB_CLK / DIU_CLK */ - - /* Calculate the pixel clock with the smallest error */ - /* calculate the following in steps to avoid overflow */ - pr_debug("DIU pixclock in ps - %d\n", pixclock); - temp = (1000000000 / pixclock) * 1000; - pixclock = temp; - pr_debug("DIU pixclock freq - %u\n", pixclock); - - temp = temp / 20; /* pixclock * 0.05 */ - pr_debug("deviation = %d\n", temp); - minpixclock = pixclock - temp; - maxpixclock = pixclock + temp; - pr_debug("DIU minpixclock - %lu\n", minpixclock); - pr_debug("DIU maxpixclock - %lu\n", maxpixclock); - pixval = speed/pixclock; - pr_debug("DIU pixval = %lu\n", pixval); - - err = LONG_MAX; - bestval = pixval; - pr_debug("DIU bestval = %lu\n", bestval); - - bestfreq = 0; - for (i = -1; i <= 1; i++) { - temp = speed / (pixval+i); - pr_debug("DIU test pixval i=%d, pixval=%lu, temp freq. = %u\n", - i, pixval, temp); - if ((temp < minpixclock) || (temp > maxpixclock)) - pr_debug("DIU exceeds monitor range (%lu to %lu)\n", - minpixclock, maxpixclock); - else if (abs(temp - pixclock) < err) { - pr_debug("Entered the else if block %d\n", i); - err = abs(temp - pixclock); - bestval = pixval + i; - bestfreq = temp; - } + /* + * convert the picoseconds spec into the desired clock rate, + * determine the acceptable clock range for the monitor (+/- 5%), + * do the calculation in steps to avoid integer overflow + */ + pr_debug("DIU pixclock in ps - %u\n", pixclock); + pixclock = (1000000000 / pixclock) * 1000; + pr_debug("DIU pixclock freq - %u\n", pixclock); + epsilon = pixclock / 20; /* pixclock * 0.05 */ + pr_debug("DIU deviation - %lu\n", epsilon); + minpixclock = pixclock - epsilon; + maxpixclock = pixclock + epsilon; + pr_debug("DIU minpixclock - %lu\n", minpixclock); + pr_debug("DIU maxpixclock - %lu\n", maxpixclock); + + /* + * check whether the DIU supports the desired pixel clock + * + * - simply request the desired clock and see what the + * platform's clock driver will make of it, assuming that it + * will setup the best approximation of the requested value + * - try other candidate frequencies in the order of decreasing + * preference (i.e. with increasing distance from the desired + * pixel clock, and checking the lower frequency before the + * higher frequency to not overload the hardware) until the + * first match is found -- any potential subsequent match + * would only be as good as the former match or typically + * would be less preferrable + * + * the offset increment of pixelclock divided by 64 is an + * arbitrary choice -- it's simple to calculate, in the typical + * case we expect the first check to succeed already, in the + * worst case seven frequencies get tested (the exact center and + * three more values each to the left and to the right) before + * the 5% tolerance window is exceeded, resulting in fast enough + * execution yet high enough probability of finding a suitable + * value, while the error rate will be in the order of single + * percents + */ + for (offset = 0; offset <= epsilon; offset += pixclock / 64) { + want = pixclock - offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; + if (!offset) + continue; + want = pixclock + offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; } + if (offset <= epsilon) { + pr_debug("DIU clock accepted - %lu\n", want); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); + return; + } + pr_warn("DIU pixclock auto search unsuccessful\n"); - pr_debug("DIU chose = %lx\n", bestval); - pr_debug("DIU error = %ld\n NomPixClk ", err); - pr_debug("DIU: Best Freq = %lx\n", bestfreq); - /* Modify DIU_DIV in CCM SCFR1 */ - temp = in_be32(&ccm->scfr1); - pr_debug("DIU: Current value of SCFR1: 0x%08x\n", temp); - temp &= ~DIU_DIV_MASK; - temp |= (bestval & DIU_DIV_MASK); - out_be32(&ccm->scfr1, temp); - pr_debug("DIU: Modified value of SCFR1: 0x%08x\n", temp); - iounmap(ccm); + /* + * what is the most appropriate action to take when the search + * for an available pixel clock which is acceptable to the + * monitor has failed? disable the DIU (clock) or just provide + * a "best effort"? we go with the latter + */ + pr_warn("DIU pixclock best effort fallback (backend's choice)\n"); + clk_set_rate(clk_diu, pixclock); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); } static enum fsl_diu_monitor_port |