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Message-ID: <CAHCN7xL4+9NogrnXA1PEWorwY7JpSGBozDtHT83JvzjfinmS+A@mail.gmail.com>
Date: Mon, 17 Apr 2023 06:55:30 -0500
From: Adam Ford <aford173@...il.com>
To: Lucas Stach <l.stach@...gutronix.de>
Cc: dri-devel@...ts.freedesktop.org,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
aford@...conembedded.com,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
Andrzej Hajda <andrzej.hajda@...el.com>,
Fabio Estevam <festevam@...il.com>, m.szyprowski@...sung.com,
marex@...x.de, Robert Foss <rfoss@...nel.org>,
David Airlie <airlied@...il.com>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Jagan Teki <jagan@...rulasolutions.com>,
NXP Linux Team <linux-imx@....com>,
devicetree@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
Jonas Karlman <jonas@...boo.se>,
Sascha Hauer <s.hauer@...gutronix.de>,
Inki Dae <inki.dae@...sung.com>,
Rob Herring <robh+dt@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
Neil Armstrong <neil.armstrong@...aro.org>,
linux-kernel@...r.kernel.org,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH 1/6] drm: bridge: samsung-dsim: Support multi-lane calculations
On Mon, Apr 17, 2023 at 3:43 AM Lucas Stach <l.stach@...gutronix.de> wrote:
>
> Hi Adam,
>
> Am Samstag, dem 15.04.2023 um 05:40 -0500 schrieb Adam Ford:
> > If there is more than one lane, the HFP, HBP, and HSA is calculated in
> > bytes/pixel, then they are divided amongst the different lanes with some
> > additional overhead. This is necessary to achieve higher resolutions while
> > keeping the pixel clocks lower as the number of lanes increase.
> >
>
> In the testing I did to come up with my patch "drm: bridge: samsung-
> dsim: fix blanking packet size calculation" the number of lanes didn't
> make any difference. My testing might be flawed, as I could only
> measure the blanking after translation from MIPI DSI to DPI, so I'm
> interested to know what others did here. How did you validate the
> blanking with your patch? Would you have a chance to test my patch and
> see if it works or breaks in your setup?
Mine was purely by trial and error. I don't have a scope, nor do I
have a copy of the MIPI DSI spec, so if the image sync'd with my
monitor, I treated it as successful.
I can give yours a try, but it might be a few days since I've only
been working on this stuff a bit in my spare time.
adam
>
> Regards,
> Lucas
>
> > Signed-off-by: Adam Ford <aford173@...il.com>
> > ---
> > drivers/gpu/drm/bridge/samsung-dsim.c | 40 +++++++++++++++++++++++----
> > 1 file changed, 34 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> > index e0a402a85787..1ccbad4ea577 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -215,6 +215,7 @@
> > #define DSI_RX_FIFO_SIZE 256
> > #define DSI_XFER_TIMEOUT_MS 100
> > #define DSI_RX_FIFO_EMPTY 0x30800002
> > +#define DSI_HSYNC_PKT_OVERHEAD 6
> >
> > #define OLD_SCLK_MIPI_CLK_NAME "pll_clk"
> >
> > @@ -879,13 +880,40 @@ static void samsung_dsim_set_display_mode(struct samsung_dsim *dsi)
> > | DSIM_MAIN_VBP(m->vtotal - m->vsync_end);
> > samsung_dsim_write(dsi, DSIM_MVPORCH_REG, reg);
> >
> > - reg = DSIM_MAIN_HFP(m->hsync_start - m->hdisplay)
> > - | DSIM_MAIN_HBP(m->htotal - m->hsync_end);
> > - samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
> > + /*
> > + * If there is more than one lane, the HFP, HBP, and HSA
> > + * is calculated in bytes/pixel, then they are divided
> > + * amongst the different lanes with some additional
> > + * overhead correction
> > + */
> > + if (dsi->lanes > 1) {
> > + u32 hfp, hbp, hsa;
> > + int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format) / 8;
> > +
> > + hfp = ((m->hsync_start - m->hdisplay) * bpp) / dsi->lanes;
> > + hfp -= (hfp > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
> > +
> > + hbp = ((m->htotal - m->hsync_end) * bpp) / dsi->lanes;
> > + hbp -= (hbp > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
> >
> > - reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
> > - | DSIM_MAIN_HSA(m->hsync_end - m->hsync_start);
> > - samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
> > + hsa = ((m->hsync_end - m->hsync_start) * bpp) / dsi->lanes;
> > + hsa -= (hsa > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
> > +
> > + reg = DSIM_MAIN_HFP(hfp) | DSIM_MAIN_HBP(hbp);
> > + samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
> > +
> > + reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
> > + | DSIM_MAIN_HSA(hsa);
> > + samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
> > + } else {
> > + reg = DSIM_MAIN_HFP(m->hsync_start - m->hdisplay)
> > + | DSIM_MAIN_HBP(m->htotal - m->hsync_end);
> > + samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
> > +
> > + reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
> > + | DSIM_MAIN_HSA(m->hsync_end - m->hsync_start);
> > + samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
> > + }
> > }
> > reg = DSIM_MAIN_HRESOL(m->hdisplay, num_bits_resol) |
> > DSIM_MAIN_VRESOL(m->vdisplay, num_bits_resol);
>
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