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Message-ID: <aNQNn9EwZzCjapB6@lizhi-Precision-Tower-5810>
Date: Wed, 24 Sep 2025 11:26:23 -0400
From: Frank Li <Frank.li@....com>
To: Liu Ying <victor.liu@....com>
Cc: Philipp Zabel <p.zabel@...gutronix.de>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
Dmitry Baryshkov <lumag@...nel.org>,
dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/14] drm/imx: dc: Add DPR channel support
On Wed, Sep 24, 2025 at 02:41:50PM +0800, Liu Ying wrote:
> On 09/23/2025, Frank Li wrote:
> > On Tue, Sep 23, 2025 at 10:07:57AM +0800, Liu Ying wrote:
> >> Display Prefetch Resolve Channel(DPRC) is a part of a prefetch engine.
> >> It fetches display data, transforms it to linear format and stores it
> >> to DPRC's RTRAM. PRG, as the other part of a prefetch engine, acts as
> >> a gasket between the RTRAM controller and a FetchUnit. Add a platform
> >> driver to support the DPRC.
> >>
> >> Signed-off-by: Liu Ying <victor.liu@....com>
> >> ---
> >> v2:
> >> - Manage clocks with bulk interfaces. (Frank)
> >> - Sort variables in probe function in reverse Christmas tree fashion. (Frank)
> >> ---
> >> drivers/gpu/drm/imx/dc/Kconfig | 1 +
> >> drivers/gpu/drm/imx/dc/Makefile | 6 +-
> >> drivers/gpu/drm/imx/dc/dc-dprc.c | 465 +++++++++++++++++++++++++++++++++++++++
> >> drivers/gpu/drm/imx/dc/dc-dprc.h | 35 +++
> >> drivers/gpu/drm/imx/dc/dc-drv.c | 1 +
> >> drivers/gpu/drm/imx/dc/dc-drv.h | 1 +
> >> drivers/gpu/drm/imx/dc/dc-prg.c | 12 +
> >> drivers/gpu/drm/imx/dc/dc-prg.h | 4 +
> >> 8 files changed, 522 insertions(+), 3 deletions(-)
> >>
> > ...
> >> +
> >> +static void dc_dprc_reset(struct dc_dprc *dprc)
> >> +{
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0 + SET, SOFT_RESET);
> >> + fsleep(20);
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0 + CLR, SOFT_RESET);
> >> + fsleep(20);
> >> +}
> >> +
> >> +static void dc_dprc_enable(struct dc_dprc *dprc)
> >> +{
> >> + dc_prg_enable(dprc->prg);
> >> +}
> >> +
> >> +static void dc_dprc_reg_update(struct dc_dprc *dprc)
> >> +{
> >> + dc_prg_reg_update(dprc->prg);
> >> +}
> >> +
> >> +static void dc_dprc_enable_ctrl_done_irq(struct dc_dprc *dprc)
> >> +{
> >> + guard(spinlock_irqsave)(&dprc->lock);
> >> + regmap_write(dprc->reg, IRQ_MASK + CLR, IRQ_DPR_CRTL_DONE);
> >> +}
> >> +
> >> +void dc_dprc_configure(struct dc_dprc *dprc, unsigned int stream_id,
> >> + unsigned int width, unsigned int height,
> >> + unsigned int stride,
> >> + const struct drm_format_info *format,
> >> + dma_addr_t baddr, bool start)
> >> +{
> >> + unsigned int prg_stride = width * format->cpp[0];
> >> + unsigned int bpp = format->cpp[0] * 8;
> >> + struct device *dev = dprc->dev;
> >> + unsigned int p1_w, p1_h;
> >> + u32 val;
> >> + int ret;
> >> +
> >> + if (start) {
> >> + ret = pm_runtime_resume_and_get(dev);
> >> + if (ret < 0) {
> >> + dev_err(dev, "failed to get RPM: %d\n", ret);
> >> + return;
> >> + }
> >> +
> >> + dc_dprc_set_stream_id(dprc, stream_id);
> >> + }
> >> +
> >> + p1_w = round_up(width, format->cpp[0] == 2 ? 32 : 16);
> >> + p1_h = round_up(height, 4);
> >> +
> >> + regmap_write(dprc->reg, FRAME_CTRL0, PITCH(stride));
> >> + regmap_write(dprc->reg, FRAME_1P_CTRL0, BYTE_1K);
> >> + regmap_write(dprc->reg, FRAME_1P_PIX_X_CTRL, NUM_X_PIX_WIDE(p1_w));
> >> + regmap_write(dprc->reg, FRAME_1P_PIX_Y_CTRL, NUM_Y_PIX_HIGH(p1_h));
> >> + regmap_write(dprc->reg, FRAME_1P_BASE_ADDR_CTRL0, baddr);
> >> + regmap_write(dprc->reg, FRAME_PIX_X_ULC_CTRL, CROP_ULC_X(0));
> >> + regmap_write(dprc->reg, FRAME_PIX_Y_ULC_CTRL, CROP_ULC_Y(0));
> >> +
> >> + regmap_write(dprc->reg, RTRAM_CTRL0, THRES_LOW(3) | THRES_HIGH(7));
> >
> > Is it okay to access register if start is false since
> > pm_runtime_resume_and_get() have not called.
>
> Yes, it is okay, because dc_dprc_configure() is supposed to be called
> continously for multiple times(OFC, fine for only once as well). For
> the first time, start is true in order to enable the DPRC. After the
> first time(DPRC is running), it is called with start == false to do
> things like page-flip(update frame buffer address).
>
> >
> >> +
> >> + val = LINE4 | BUF2;
> >> + switch (format->format) {
> >> + case DRM_FORMAT_XRGB8888:
> >> + /*
> >> + * It turns out pixel components are mapped directly
> >> + * without position change via DPR processing with
> >> + * the following color component configurations.
> >> + * Leave the pixel format to be handled by the
> >> + * display controllers.
> >> + */
> >> + val |= A_COMP_SEL(3) | R_COMP_SEL(2) |
> >> + G_COMP_SEL(1) | B_COMP_SEL(0);
> >> + val |= PIX_SIZE_32BIT;
> >> + break;
> >> + default:
> >> + dev_err(dev, "unsupported format 0x%08x\n", format->format);
> >> + return;
> >> + }
> >> + regmap_write(dprc->reg, MODE_CTRL0, val);
> >> +
> >> + if (start) {
> >> + /* software shadow load for the first frame */
> >> + val = SW_SHADOW_LOAD_SEL | SHADOW_LOAD_EN;
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0, val);
> >> +
> >> + /* and then, run... */
> >> + val |= RUN_EN | REPEAT_EN;
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0, val);
> >> + }
> >> +
> >> + dc_prg_configure(dprc->prg, width, height, prg_stride, bpp, baddr, start);
> >> +
> >> + dc_dprc_enable(dprc);
> >> +
> >> + dc_dprc_reg_update(dprc);
> >> +
> >> + if (start)
> >> + dc_dprc_enable_ctrl_done_irq(dprc);
> >> +
> >> + dev_dbg(dev, "w: %u, h: %u, s: %u, fmt: 0x%08x\n",
> >> + width, height, stride, format->format);
> >> +}
> >> +
> >> +void dc_dprc_disable_repeat_en(struct dc_dprc *dprc)
> >> +{
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0 + CLR, REPEAT_EN);
> >> + dev_dbg(dprc->dev, "disable REPEAT_EN\n");
> >> +}
> >> +
> >> +void dc_dprc_disable(struct dc_dprc *dprc)
> >> +{
> >> + dc_prg_disable(dprc->prg);
> >> +
> >> + pm_runtime_put(dprc->dev);
> >
> > You call pm_runtime_put() in dc_dprc_disable(), but not call
> > pm_runtime_resume_and_get() at dc_dprc_enable().
>
> Yes, dc_dprc_configure()(start == true) is designed to get RPM and
> dc_dprc_disable() to put RPM.
>
> dc_dprc_enable() just sets PRG to non-bypass mode.
>
> >
> > Is it more reasonable to call pm_runtime_resume_and_get() in dc_dprc_enable()
> >
> > dc_dprc_enable()
> > {
> > ...
> > pm_runtime_resume_and_get();
> > }
> >
> > dc_dprc_configure()
> > {
> > unconditional call
> > pm_runtime_resume_and_get()
> > ...
> > pm_runtime_put()
>
> Here, as RPM is put, it's possible to actually disable the power domain,
> hence possibly lose all the DPRC configuration done between RPM get and
> RPM put. So, this doesn't make sense.
>
Okay,
dc_dprc_enable()
{
...
pm_runtime_resume_and_get();
}
dc_dpdr_disable()
{
pm_runtime_put();
}
dc_dprc_configure()
{
pm_runtime_resume_and_get();
if (start)
dc_dprc_enable(dprc);
pm_runtime_put();
}
Look more reasonable for pair get()/put(). after first start, ref count
will not reduce 0 by pm_runtime_put();.
> >
> > if (start) //look like only need enable when start is true
>
> I may add this check in next version.
>
> > dc_dprc_enable(dprc);
> > }
> >
> >> +
> >> + dev_dbg(dprc->dev, "disable\n");
> >> +}
> >> +
> >> +void dc_dprc_disable_at_boot(struct dc_dprc *dprc)
> >> +{
> >> + dc_prg_disable_at_boot(dprc->prg);
> >> +
> >> + clk_bulk_disable_unprepare(dprc->num_clks, dprc->clks);
> >> +
> >
> > you have runtime functions dc_dprc_runtime_suspend()
> >
> > If runtime pm status is correct, needn't call clk_bulk_disable_unprepare().
> >
> > Look like call pm_runtime_put() here to let runtime pm management clks.
> >
> > otherwise, runtime pm state will not match clock enable/disable state.
> >
> >> + dev_dbg(dprc->dev, "disable at boot\n");
> >> +}
> >> +
> >> +static void dc_dprc_ctrl_done_handle(struct dc_dprc *dprc)
> >> +{
> >> + regmap_write(dprc->reg, SYSTEM_CTRL0, REPEAT_EN);
> >> +
> >> + dc_prg_shadow_enable(dprc->prg);
> >> +
> >> + dev_dbg(dprc->dev, "CTRL done handle\n");
> >> +}
> >> +
> > ...
> >> +
> >> +static int dc_dprc_probe(struct platform_device *pdev)
> >> +{
> >> + struct device *dev = &pdev->dev;
> >> + struct device_node *np = dev->of_node;
> >> + struct resource *res;
> >> + struct dc_dprc *dprc;
> >> + void __iomem *base;
> >> + int ret, wrap_irq;
> >> +
> >> + dprc = devm_kzalloc(dev, sizeof(*dprc), GFP_KERNEL);
> >> + if (!dprc)
> >> + return -ENOMEM;
> >> +
> >> + ret = imx_scu_get_handle(&dprc->ipc_handle);
> >> + if (ret)
> >> + return dev_err_probe(dev, ret, "failed to get SCU ipc handle\n");
> >> +
> >> + base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> >> + if (IS_ERR(base))
> >> + return PTR_ERR(base);
> >> +
> >> + dprc->reg = devm_regmap_init_mmio(dev, base, &dc_dprc_regmap_config);
> >> + if (IS_ERR(dprc->reg))
> >> + return PTR_ERR(dprc->reg);
> >> +
> >> + wrap_irq = platform_get_irq_byname(pdev, "dpr_wrap");
> >> + if (wrap_irq < 0)
> >> + return -ENODEV;
> >> +
> >> + dprc->num_clks = devm_clk_bulk_get_all(dev, &dprc->clks);
> >> + if (dprc->num_clks < 0)
> >> + return dev_err_probe(dev, dprc->num_clks, "failed to get clocks\n");
> >> +
> >> + ret = of_property_read_u32(np, "fsl,sc-resource", &dprc->sc_resource);
> >> + if (ret) {
> >> + dev_err(dev, "failed to get SC resource %d\n", ret);
> >> + return ret;
> >> + }
> >> +
> >> + dprc->prg = dc_prg_lookup_by_phandle(dev, "fsl,prgs", 0);
> >> + if (!dprc->prg)
> >> + return dev_err_probe(dev, -EPROBE_DEFER,
> >> + "failed to lookup PRG\n");
> >> +
> >> + dc_prg_set_dprc(dprc->prg, dprc);
> >> +
> >> + dprc->dev = dev;
> >> + spin_lock_init(&dprc->lock);
> >> +
> >> + ret = devm_request_irq(dev, wrap_irq, dc_dprc_wrap_irq_handler,
> >> + IRQF_SHARED, dev_name(dev), dprc);
> >> + if (ret < 0) {
> >> + dev_err(dev, "failed to request dpr_wrap IRQ(%d): %d\n",
> >> + wrap_irq, ret);
> >> + return ret;
> >> + }
> >> +
> >> + dev_set_drvdata(dev, dprc);
> >> +
> >> + ret = devm_pm_runtime_enable(dev);
> >> + if (ret)
> >> + return dev_err_probe(dev, ret, "failed to enable PM runtime\n");
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int dc_dprc_runtime_suspend(struct device *dev)
> >> +{
> >> + struct dc_dprc *dprc = dev_get_drvdata(dev);
> >> +
> >> + clk_bulk_disable_unprepare(dprc->num_clks, dprc->clks);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int dc_dprc_runtime_resume(struct device *dev)
> >> +{
> >> + struct dc_dprc *dprc = dev_get_drvdata(dev);
> >> + int ret;
> >> +
> >> + ret = clk_bulk_prepare_enable(dprc->num_clks, dprc->clks);
> >> + if (ret) {
> >> + dev_err(dev, "failed to enable clocks: %d\n", ret);
> >> + return ret;
> >> + }
> >> +
> >> + dc_dprc_reset(dprc);
> >> +
> >> + /* disable all control IRQs and enable all error IRQs */
> >> + guard(spinlock_irqsave)(&dprc->lock);
> >> + regmap_write(dprc->reg, IRQ_MASK, IRQ_CTRL_MASK);
> >
> > write one 32bit register is atomic, look like needn't spinlock.
> >
> > Only other place use dprc->lock is in dc_dprc_enable_ctrl_done_irq(), which
> > write 32bit clr register.
>
> No, dc_dprc_wrap_irq_handler() uses the lock to protect register access too,
> so it's needed.
guard only protect after it.
in dc_dprc_runtime_resume()
+ /* disable all control IRQs and enable all error IRQs */
+ guard(spinlock_irqsave)(&dprc->lock);
+ regmap_write(dprc->reg, IRQ_MASK, IRQ_CTRL_MASK);
+
+ return 0;
+static void dc_dprc_enable_ctrl_done_irq(struct dc_dprc *dprc)
+{
+ guard(spinlock_irqsave)(&dprc->lock);
+ regmap_write(dprc->reg, IRQ_MASK + CLR, IRQ_DPR_CRTL_DONE);
+}
How spin lock protect register access?
1: IRQ_MASK <= IRQ_CTRL_MASK;
2: IRQ_MASK + CLR <= IRQ_DPR_CRTL_DONE;
2 possilbe result:
1 happen after 2
2 happen after 1
Frank
>
> >
> > Frank
> >> +
> >> + return 0;
> >> +}
> >> +
> > ...
> >> +void dc_prg_set_dprc(struct dc_prg *prg, struct dc_dprc *dprc)
> >> +{
> >> + prg->dprc = dprc;
> >> +}
> >> +
> >> +struct dc_dprc *dc_prg_get_dprc(struct dc_prg *prg)
> >> +{
> >> + return prg->dprc;
> >> +}
> >> +
> >> static int dc_prg_probe(struct platform_device *pdev)
> >> {
> >> struct device *dev = &pdev->dev;
> >> diff --git a/drivers/gpu/drm/imx/dc/dc-prg.h b/drivers/gpu/drm/imx/dc/dc-prg.h
> >> index 6fd9b050bfa12334720f83ff9ceaf337e3048a54..f29d154f7de597b9d20d5e71303049f6f8b022d6 100644
> >> --- a/drivers/gpu/drm/imx/dc/dc-prg.h
> >> +++ b/drivers/gpu/drm/imx/dc/dc-prg.h
> >> @@ -32,4 +32,8 @@ bool dc_prg_stride_supported(struct dc_prg *prg,
> >> struct dc_prg *
> >> dc_prg_lookup_by_phandle(struct device *dev, const char *name, int index);
> >>
> >> +void dc_prg_set_dprc(struct dc_prg *prg, struct dc_dprc *dprc);
> >> +
> >> +struct dc_dprc *dc_prg_get_dprc(struct dc_prg *prg);
> >> +
> >> #endif
> >>
> >> --
> >> 2.34.1
> >>
>
>
> --
> Regards,
> Liu Ying
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