From: Chris Zhong <zyw@rock-chips.com>
To: John Keeping <john@metanate.com>, Mark Yao <mark.yao@rock-chips.com>
Cc: linux-rockchip@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 19/26] drm/rockchip: dw-mipi-dsi: improve PLL configuration
Date: Mon, 23 Jan 2017 09:38:54 +0800 [thread overview]
Message-ID: <58855EAE.2010704@rock-chips.com> (raw)
In-Reply-To: <20170121163128.22240-20-john@metanate.com>
Hi John
On 01/22/2017 12:31 AM, John Keeping wrote:
> 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
This formula is limit for N, but we still can not guarantee to get an
even M.
Do you think we should do a check for M.
such as:
if (m % 2)
continue;
...
for (i = pllref / 5; i > (pllref / 40); i--) {
pre = pllref / i;
if ((tmp > (target_mbps % pre)) && (target_mbps / pre < 512)) {
tmp = target_mbps % pre;
n = i;
m = target_mbps / pre;
if (m % 2)
continue;
}
if (tmp == 0)
break;
}
if (m % 2)
m++;
dsi->lane_mbps = pllref / n * m;
dsi->input_div = n;
dsi->feedback_div = m;
>
> Signed-off-by: John Keeping <john@metanate.com>
> ---
> 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 12432e41971b..f2320cf1366c 100644
> --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> @@ -519,7 +519,7 @@ 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;
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next prev parent reply other threads:[~2017-01-23 1:38 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-21 16:31 [PATCH v2 00/26] drm/rockchip: MIPI fixes & improvements John Keeping
2017-01-21 16:31 ` [PATCH v2 01/26] drm/rockchip: dw-mipi-dsi: don't configure hardware in mode_set for MIPI John Keeping
2017-01-22 3:58 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 02/26] drm/rockchip: dw-mipi-dsi: rename commit hook to enable John Keeping
2017-01-21 16:31 ` [PATCH v2 03/26] drm/rockchip: dw-mipi-dsi: pass mode in where needed John Keeping
2017-01-22 4:00 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 04/26] drm/rockchip: dw-mipi-dsi: remove mode_set hook John Keeping
2017-01-22 6:08 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 05/26] drm/rockchip: dw-mipi-dsi: fix command header writes John Keeping
2017-01-21 16:31 ` [PATCH v2 06/26] drm/rockchip: dw-mipi-dsi: fix generic packet status check John Keeping
2017-01-22 6:24 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 07/26] drm/rockchip: dw-mipi-dsi: avoid out-of-bounds read on tx_buf John Keeping
2017-01-22 6:42 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 08/26] drm/rockchip: dw-mipi-dsi: include bad value in error message John Keeping
2017-01-22 6:44 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 09/26] drm/rockchip: dw-mipi-dsi: respect message flags John Keeping
2017-01-22 7:14 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 10/26] drm/rockchip: dw-mipi-dsi: only request HS clock when required John Keeping
2017-01-22 8:10 ` Chris Zhong
[not found] ` <20170121163128.22240-1-john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>
2017-01-21 16:31 ` [PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned John Keeping
2017-01-22 8:16 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 12/26] drm/rockchip: dw-mipi-dsi: prepare panel after phy init John Keeping
2017-01-22 8:22 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 13/26] drm/rockchip: dw-mipi-dsi: allow commands in panel_disable John Keeping
2017-01-22 8:37 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 14/26] drm/rockchip: dw-mipi-dsi: fix escape clock rate John Keeping
2017-01-22 9:37 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 15/26] drm/rockchip: dw-mipi-dsi: ensure PHY is reset John Keeping
2017-01-22 9:37 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 16/26] drm/rockchip: dw-mipi-dsi: configure bias and bandgap before enable John Keeping
2017-01-21 16:31 ` [PATCH v2 17/26] drm/rockchip: dw-mipi-dsi: don't enable PHY PLL until it's configured John Keeping
2017-01-22 10:07 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 18/26] drm/rockchip: dw-mipi-dsi: properly configure PHY timing John Keeping
2017-01-22 3:06 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 19/26] drm/rockchip: dw-mipi-dsi: improve PLL configuration John Keeping
2017-01-23 1:38 ` Chris Zhong [this message]
2017-01-23 12:49 ` John Keeping
2017-01-24 2:42 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 20/26] drm/rockchip: dw-mipi-dsi: use specific poll helper John Keeping
2017-01-23 0:49 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 21/26] drm/rockchip: dw-mipi-dsi: use positive check for N{H, V}SYNC John Keeping
2017-01-21 16:31 ` [PATCH v2 22/26] drm/rockchip: vop: test for P{H,V}SYNC John Keeping
2017-01-23 7:12 ` Mark yao
2017-01-21 16:31 ` [PATCH v2 23/26] drm/rockchip: dw-mipi-dsi: defer probe if panel is not loaded John Keeping
2017-01-21 16:31 ` [PATCH v2 24/26] drm/rockchip: dw-mipi-dsi: support non-burst modes John Keeping
2017-01-23 6:11 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 25/26] drm/rockchip: dw-mipi-dsi: add reset control John Keeping
2017-01-23 6:12 ` Chris Zhong
2017-01-21 16:31 ` [PATCH v2 26/26] drm/rockchip: dw-mipi-dsi: support read commands John Keeping
2017-01-22 3:08 ` Chris Zhong
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