diff options
| author | Peter Rosin <peda@axentia.se> | 2018-08-24 11:24:57 +0200 |
|---|---|---|
| committer | Boris Brezillon <boris.brezillon@bootlin.com> | 2018-08-27 21:12:16 +0200 |
| commit | 319711f982084b044d3dac6ae58e3d801ae4ca43 (patch) | |
| tree | 6951c63c46b7ba9cb3d30430fe93ecd11d6e1c8b /drivers/gpu/drm/atmel-hlcdc | |
| parent | bf1178c9893018b77c829215970cf4c6a3cebb34 (diff) | |
| download | linux-319711f982084b044d3dac6ae58e3d801ae4ca43.tar.bz2 | |
drm/atmel-hlcdc: prefer a higher rate clock as pixel-clock base
If the divider used to get the pixel-clock is small, the granularity
of the frequencies possible for the pixel-clock is quite coarse. E.g.
requesting a pixel-clock of 65MHz with a sys_clk of 132MHz results
in the divider being set to 3 ending up with 44MHz.
By preferring the doubled sys_clk as base, the divider instead ends
up as 5 yielding a pixel-clock of 52.8Mhz, which is a definite
improvement.
While at it, clamp the divider so that it does not overflow in case
it gets big.
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180824092458.13165-2-peda@axentia.se
Diffstat (limited to 'drivers/gpu/drm/atmel-hlcdc')
| -rw-r--r-- | drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c index d73281095fac..ec209dec224d 100644 --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c @@ -101,18 +101,22 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c) (adj->crtc_hdisplay - 1) | ((adj->crtc_vdisplay - 1) << 16)); - cfg = 0; + cfg = ATMEL_HLCDC_CLKSEL; - prate = clk_get_rate(crtc->dc->hlcdc->sys_clk); + prate = 2 * clk_get_rate(crtc->dc->hlcdc->sys_clk); mode_rate = adj->crtc_clock * 1000; - if ((prate / 2) < mode_rate) { - prate *= 2; - cfg |= ATMEL_HLCDC_CLKSEL; - } div = DIV_ROUND_UP(prate, mode_rate); - if (div < 2) + if (div < 2) { div = 2; + } else if (ATMEL_HLCDC_CLKDIV(div) & ~ATMEL_HLCDC_CLKDIV_MASK) { + /* The divider ended up too big, try a lower base rate. */ + cfg &= ~ATMEL_HLCDC_CLKSEL; + prate /= 2; + div = DIV_ROUND_UP(prate, mode_rate); + if (ATMEL_HLCDC_CLKDIV(div) & ~ATMEL_HLCDC_CLKDIV_MASK) + div = ATMEL_HLCDC_CLKDIV_MASK; + } cfg |= ATMEL_HLCDC_CLKDIV(div); |