The multiplication ratio for the PLL is required to be even due to the use of a "by 2 pre-scaler". Currently we are likely to end up with an odd multiplier even though there is an equivalent set of parameters with an even multiplier.
For example, using the 324MHz bit rate with a reference clock of 24MHz we end up with M = 27, N = 2 whereas the example in the PHY databook gives M = 54, N = 4 for this bit rate and reference clock.
By walking down through the available multiplier instead of up we are more likely to hit an even multiplier. With the above example we do now get M = 54, N = 4 as given by the databook.
While doing this, change the loop limits to encode the actual limits on the divisor, which are:
40MHz >= (pllref / N) >= 5MHz
Signed-off-by: John Keeping john@metanate.com --- Unchanged in v3 Unchanged in v2
drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c index 85edf6dd2bac..dcb66a21e1f1 100644 --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c @@ -522,7 +522,7 @@ static int dw_mipi_dsi_get_lane_bps(struct dw_mipi_dsi *dsi, pllref = DIV_ROUND_UP(clk_get_rate(dsi->pllref_clk), USEC_PER_SEC); tmp = pllref;
- for (i = 1; i < 6; i++) { + for (i = pllref / 5; i > (pllref / 40); i--) { pre = pllref / i; if ((tmp > (target_mbps % pre)) && (target_mbps / pre < 512)) { tmp = target_mbps % pre;