From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933094AbcLIDvc (ORCPT ); Thu, 8 Dec 2016 22:51:32 -0500 Received: from mail.kmu-office.ch ([178.209.48.109]:40661 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753198AbcLIDvb (ORCPT ); Thu, 8 Dec 2016 22:51:31 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Thu, 08 Dec 2016 19:44:56 -0800 From: Stefan Agner To: Marek Vasut Cc: airlied@linux.ie, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/mxsfb: use bus_format to determine LCD bus width In-Reply-To: <878d504a-5689-1dd9-2e5e-fad085b7406e@denx.de> References: <20161208225243.19792-1-stefan@agner.ch> <878d504a-5689-1dd9-2e5e-fad085b7406e@denx.de> Message-ID: <5674d93cf27dbb027f8a5ec448169b0c@agner.ch> User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016-12-08 15:33, Marek Vasut wrote: > On 12/08/2016 11:52 PM, Stefan Agner wrote: >> The LCD bus width does not need to align with the pixel format. The >> LCDIF controller automatically converts between pixel formats and >> bus width by padding or dropping LSBs. >> >> The DRM subsystem has the notion of bus_format which allows to >> determine what bus_formats are supported by the display. Choose the >> first available or fallback to 24 bit if none are available. >> >> Signed-off-by: Stefan Agner >> --- >> drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 28 +++++++++++++++++++++++++--- >> drivers/gpu/drm/mxsfb/mxsfb_regs.h | 1 + >> 2 files changed, 26 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c >> index 4bcc8a3..00fa244 100644 >> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c >> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c >> @@ -65,13 +65,11 @@ static int mxsfb_set_pixel_fmt(struct mxsfb_drm_private *mxsfb) > > You should probably drop the WARNING: comment in this function too. > >> switch (format) { >> case DRM_FORMAT_RGB565: >> dev_dbg(drm->dev, "Setting up RGB565 mode\n"); >> - ctrl |= CTRL_SET_BUS_WIDTH(STMLCDIF_16BIT); >> ctrl |= CTRL_SET_WORD_LENGTH(0); >> ctrl1 |= CTRL1_SET_BYTE_PACKAGING(0xf); >> break; >> case DRM_FORMAT_XRGB8888: >> dev_dbg(drm->dev, "Setting up XRGB8888 mode\n"); >> - ctrl |= CTRL_SET_BUS_WIDTH(STMLCDIF_24BIT); >> ctrl |= CTRL_SET_WORD_LENGTH(3); >> /* Do not use packed pixels = one pixel per word instead. */ >> ctrl1 |= CTRL1_SET_BYTE_PACKAGING(0x7); >> @@ -89,6 +87,9 @@ static int mxsfb_set_pixel_fmt(struct mxsfb_drm_private *mxsfb) >> >> static void mxsfb_enable_controller(struct mxsfb_drm_private *mxsfb) >> { >> + struct drm_crtc *crtc = &mxsfb->pipe.crtc; >> + struct drm_device *drm = crtc->dev; >> + u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24; > > So why do you move the bus width configuration from > mxsfb_set_pixel_fmt() to here ? Is there any reason > for it? > To emphasize that it is not related to pixel format. Also, if you have a controller with multiple framebuffers/layers, mxsfb_set_pixel_fmt would get called per layer... In a full DRM driver it probably would be part of a encoder function, I feel here it seems to map best to enable controller. It could probably also be in mxsfb_crtc_enable (or even mxsfb_crtc_mode_set_nofb I guess), but we do not touch LCDC_CTRL there... >> u32 reg; >> >> if (mxsfb->clk_disp_axi) >> @@ -97,7 +98,28 @@ static void mxsfb_enable_controller(struct mxsfb_drm_private *mxsfb) >> mxsfb_enable_axi_clk(mxsfb); >> >> /* If it was disabled, re-enable the mode again */ >> - writel(CTRL_DOTCLK_MODE, mxsfb->base + LCDC_CTRL + REG_SET); >> + reg = readl(mxsfb->base + LCDC_CTRL); > > Wouldn't it make more sense to cache the LCDC_CTRL content rather than > doing R-M-W on it ? > Not sure what you mean by cache? Isn't the variable reg counting as a cache? >> + reg |= CTRL_DOTCLK_MODE; >> + >> + if (mxsfb->connector.display_info.num_bus_formats) >> + bus_format = mxsfb->connector.display_info.bus_formats[0]; >> + >> + reg &= ~CTRL_BUS_WIDTH_MASK; >> + switch (bus_format) { >> + case MEDIA_BUS_FMT_RGB565_1X16: >> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_16BIT); >> + break; >> + case MEDIA_BUS_FMT_RGB666_1X18: >> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_18BIT); >> + break; >> + case MEDIA_BUS_FMT_RGB888_1X24: >> + reg |= CTRL_SET_BUS_WIDTH(STMLCDIF_24BIT); >> + break; >> + default: >> + dev_err(drm->dev, "Unknown media bus format %d\n", bus_format); >> + break; >> + } >> + writel(reg, mxsfb->base + LCDC_CTRL); > > On MX6SX: > Tested-by: Marek Vasut Thx! -- Stefan