From: "Noralf Trønnes" <noralf@tronnes.org> To: Eric Anholt <eric@anholt.net>, dri-devel@lists.freedesktop.org, Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>, devicetree@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Heiner Kallweit <hkallweit1@gmail.com> Subject: Re: [PATCH 0/3] drm: tinydrm driver for adafruit PiTFT 3.5" touchscreen Date: Thu, 25 Oct 2018 23:52:35 +0200 [thread overview] Message-ID: <2e548bd7-81f3-5952-b5de-96c26c9f6b19@tronnes.org> (raw) In-Reply-To: <87h8harnv4.fsf@anholt.net> Den 25.10.2018 18.29, skrev Eric Anholt: > Eric Anholt <eric@anholt.net> writes: > >> I was going to start working on making the vc4 driver work with >> tinydrm panels, but it turned out tinydrm didn't have the panel I had >> previously bought. So, last night I ported the fbtft staging >> driver over to DRM. >> >> It seems to work (with DT at >> https://github.com/anholt/linux/commits/drm-misc-next-hx8357d) -- >> fbdev works great including rotated, and so does modetest. However, >> when X11 comes up at 16bpp, I get: >> >> https://photos.app.goo.gl/8tuhzPFFoDGamEfk8 >> >> If I have tinydrm set a preferred bpp of 24, X looks great. Noralf, >> any ideas? > Also, with these patches and the format modifier patch I just sent, mesa > with vc4 is now working with this driver on this branch: > > https://gitlab.freedesktop.org/anholt/mesa/commits/kmsro Ah, nice to see this happening! Getting hw rendering was one of the advantages I saw DRM could provide over fbdev on these displays. Little did I know how complicated graphics was outside fbdev, so I was unable to realise this myself. The current solution to get hw rendering is to have a userspace process that continously copies the framebuffer: https://github.com/tasanakorn/rpi-fbcp It's used by some of the small DIY handheld game consoles that run emulators which requires hw rendering. > Now I wonder how we can improve performance of the SPI updates. At what SPI speed are you running? The datasheet for most of these display controllers list the max speed as 10MHz, but almost all of them can go faster. Some are reported going as high as 70-80MHz. That's for the pixel data transfer, not the commands. tinydrm/mipi-dbi.c sends commands at 10MHz and pixels at full speed (mipi_dbi_spi_cmd_max_speed()). Most panels I have run at 32MHz or 48MHz. Almost all the time is spent in the SPI transfer, so every hz counts. On the Pi there's byte swapping because the DMA capable SPI controller can't do 16-bit (tinydrm_swab16()). If I remember correctly this has negligible impact on performance. The SPI controller/driver on the Pi has some restrictions on the speeds to choose from because the divisor has to be a multiple of two (bcm2835_spi_transfer_one()). A full update on a 320x480 RGB565 panel is 262.5kB, so it's a lot to push over SPI. A 2.8" 320x240 panel is more suitable for video fps, because of the lower resolution. I'll look at the patches during the weekend. Noralf.
WARNING: multiple messages have this Message-ID (diff)
From: "Noralf Trønnes" <noralf@tronnes.org> To: Eric Anholt <eric@anholt.net>, dri-devel@lists.freedesktop.org, Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>, devicetree@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Heiner Kallweit <hkallweit1@gmail.com> Subject: Re: [PATCH 0/3] drm: tinydrm driver for adafruit PiTFT 3.5" touchscreen Date: Thu, 25 Oct 2018 23:52:35 +0200 [thread overview] Message-ID: <2e548bd7-81f3-5952-b5de-96c26c9f6b19@tronnes.org> (raw) In-Reply-To: <87h8harnv4.fsf@anholt.net> Den 25.10.2018 18.29, skrev Eric Anholt: > Eric Anholt <eric@anholt.net> writes: > >> I was going to start working on making the vc4 driver work with >> tinydrm panels, but it turned out tinydrm didn't have the panel I had >> previously bought. So, last night I ported the fbtft staging >> driver over to DRM. >> >> It seems to work (with DT at >> https://github.com/anholt/linux/commits/drm-misc-next-hx8357d) -- >> fbdev works great including rotated, and so does modetest. However, >> when X11 comes up at 16bpp, I get: >> >> https://photos.app.goo.gl/8tuhzPFFoDGamEfk8 >> >> If I have tinydrm set a preferred bpp of 24, X looks great. Noralf, >> any ideas? > Also, with these patches and the format modifier patch I just sent, mesa > with vc4 is now working with this driver on this branch: > > https://gitlab.freedesktop.org/anholt/mesa/commits/kmsro Ah, nice to see this happening! Getting hw rendering was one of the advantages I saw DRM could provide over fbdev on these displays. Little did I know how complicated graphics was outside fbdev, so I was unable to realise this myself. The current solution to get hw rendering is to have a userspace process that continously copies the framebuffer: https://github.com/tasanakorn/rpi-fbcp It's used by some of the small DIY handheld game consoles that run emulators which requires hw rendering. > Now I wonder how we can improve performance of the SPI updates. At what SPI speed are you running? The datasheet for most of these display controllers list the max speed as 10MHz, but almost all of them can go faster. Some are reported going as high as 70-80MHz. That's for the pixel data transfer, not the commands. tinydrm/mipi-dbi.c sends commands at 10MHz and pixels at full speed (mipi_dbi_spi_cmd_max_speed()). Most panels I have run at 32MHz or 48MHz. Almost all the time is spent in the SPI transfer, so every hz counts. On the Pi there's byte swapping because the DMA capable SPI controller can't do 16-bit (tinydrm_swab16()). If I remember correctly this has negligible impact on performance. The SPI controller/driver on the Pi has some restrictions on the speeds to choose from because the divisor has to be a multiple of two (bcm2835_spi_transfer_one()). A full update on a 320x480 RGB565 panel is 262.5kB, so it's a lot to push over SPI. A 2.8" 320x240 panel is more suitable for video fps, because of the lower resolution. I'll look at the patches during the weekend. Noralf. _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2018-10-25 21:52 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-10-24 18:43 [PATCH 0/3] drm: tinydrm driver for adafruit PiTFT 3.5" touchscreen Eric Anholt 2018-10-24 18:43 ` [PATCH 1/3] dt-bindings: new binding for Himax HX8357D display panels Eric Anholt 2018-10-25 21:42 ` Rob Herring 2018-10-27 16:10 ` Noralf Trønnes 2018-10-27 16:10 ` Noralf Trønnes 2018-10-24 18:43 ` [PATCH 2/3] drm: Add an hx8367d tinydrm driver Eric Anholt 2018-10-27 16:12 ` Noralf Trønnes 2018-10-27 16:12 ` Noralf Trønnes 2018-10-30 22:46 ` Eric Anholt 2018-10-30 22:46 ` Eric Anholt 2018-10-24 18:43 ` [PATCH 3/3] drm/tinydrm: Fix setting of the column/page end addresses Eric Anholt 2018-10-27 16:13 ` Noralf Trønnes 2018-10-27 16:13 ` Noralf Trønnes 2018-10-25 16:29 ` [PATCH 0/3] drm: tinydrm driver for adafruit PiTFT 3.5" touchscreen Eric Anholt 2018-10-25 16:29 ` Eric Anholt 2018-10-25 21:52 ` Noralf Trønnes [this message] 2018-10-25 21:52 ` Noralf Trønnes 2018-10-26 2:30 ` Eric Anholt 2018-10-26 2:30 ` Eric Anholt 2018-10-26 19:16 ` Noralf Trønnes 2018-10-26 19:16 ` Noralf Trønnes 2018-10-26 20:57 ` Noralf Trønnes 2018-10-26 20:57 ` Noralf Trønnes 2018-10-31 16:27 ` Noralf Trønnes
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=2e548bd7-81f3-5952-b5de-96c26c9f6b19@tronnes.org \ --to=noralf@tronnes.org \ --cc=devicetree@vger.kernel.org \ --cc=dri-devel@lists.freedesktop.org \ --cc=eric@anholt.net \ --cc=hkallweit1@gmail.com \ --cc=linux-kernel@vger.kernel.org \ --cc=mark.rutland@arm.com \ --cc=robh+dt@kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.