Re: [PATCH] video: mxsfb: Make sure axi clock is enabled when accessing registers

Peter Chen
2015-03-04T06:36:07Z

On Wed, Mar 04, 2015 at 01:58:55PM +0800, Liu Ying wrote:
> The LCDIF engines embedded in i.MX6sl and i.MX6sx SoCs need the axi clock
> as the engine's system clock. The clock should be enabled when accessing
> LCDIF registers, otherwise the kernel would hang up. We should also keep
> the clock being enabled when the engine is being active to scan out frames
> from memory. This patch makes sure the axi clock is enabled when accessing
> registers so that the kernel hang up issue can be fixed.
>
> Reported-by: Peter Chen <peter.chen@freescale.com>
> Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
> ---
> drivers/video/fbdev/mxsfb.c | 70 ++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 56 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/video/fbdev/mxsfb.c b/drivers/video/fbdev/mxsfb.c
> index f8ac4a4..a8cf3b2 100644
> --- a/drivers/video/fbdev/mxsfb.c
> +++ b/drivers/video/fbdev/mxsfb.c
> @@ -316,6 +316,18 @@ static int mxsfb_check_var(struct fb_var_screeninfo *var,
> return 0;
> }
>
> +static inline void mxsfb_enable_axi_clk(struct mxsfb_info *host)
> +{
> + if (host->clk_axi)
> + clk_prepare_enable(host->clk_axi);
> +}
> +
> +static inline void mxsfb_disable_axi_clk(struct mxsfb_info *host)
> +{
> + if (host->clk_axi)
> + clk_disable_unprepare(host->clk_axi);
> +}
> +
> static void mxsfb_enable_controller(struct fb_info *fb_info)
> {
> struct mxsfb_info *host = to_imxfb_host(fb_info);
> @@ -333,14 +345,13 @@ static void mxsfb_enable_controller(struct fb_info *fb_info)
> }
> }
>
> - if (host->clk_axi)
> - clk_prepare_enable(host->clk_axi);
> -
> if (host->clk_disp_axi)
> clk_prepare_enable(host->clk_disp_axi);
> clk_prepare_enable(host->clk);
> clk_set_rate(host->clk, PICOS2KHZ(fb_info->var.pixclock) * 1000U);
>
> + mxsfb_enable_axi_clk(host);
> +
> /* if it was disabled, re-enable the mode again */
> writel(CTRL_DOTCLK_MODE, host->base + LCDC_CTRL + REG_SET);
>
> @@ -380,11 +391,11 @@ static void mxsfb_disable_controller(struct fb_info *fb_info)
> reg = readl(host->base + LCDC_VDCTRL4);
> writel(reg & ~VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4);
>
> + mxsfb_disable_axi_clk(host);
> +
> clk_disable_unprepare(host->clk);
> if (host->clk_disp_axi)
> clk_disable_unprepare(host->clk_disp_axi);
> - if (host->clk_axi)
> - clk_disable_unprepare(host->clk_axi);
>
> host->enabled = 0;
>
> @@ -421,6 +432,8 @@ static int mxsfb_set_par(struct fb_info *fb_info)
> mxsfb_disable_controller(fb_info);
> }
>
> + mxsfb_enable_axi_clk(host);
> +
> /* clear the FIFOs */
> writel(CTRL1_FIFO_CLEAR, host->base + LCDC_CTRL1 + REG_SET);
>
> @@ -438,6 +451,7 @@ static int mxsfb_set_par(struct fb_info *fb_info)
> ctrl |= CTRL_SET_WORD_LENGTH(3);
> switch (host->ld_intf_width) {
> case STMLCDIF_8BIT:
> + mxsfb_disable_axi_clk(host);
> dev_err(&host->pdev->dev,
> "Unsupported LCD bus width mapping\n");
> return -EINVAL;
> @@ -451,6 +465,7 @@ static int mxsfb_set_par(struct fb_info *fb_info)
> writel(CTRL1_SET_BYTE_PACKAGING(0x7), host->base + LCDC_CTRL1);
> break;
> default:
> + mxsfb_disable_axi_clk(host);
> dev_err(&host->pdev->dev, "Unhandled color depth of %u\n",
> fb_info->var.bits_per_pixel);
> return -EINVAL;
> @@ -504,6 +519,8 @@ static int mxsfb_set_par(struct fb_info *fb_info)
> fb_info->fix.line_length * fb_info->var.yoffset,
> host->base + host->devdata->next_buf);
>
> + mxsfb_disable_axi_clk(host);
> +
> if (reenable)
> mxsfb_enable_controller(fb_info);
>
> @@ -582,10 +599,16 @@ static int mxsfb_pan_display(struct fb_var_screeninfo *var,
>
> offset = fb_info->fix.line_length * var->yoffset;
>
> + if (!host->enabled)
> + mxsfb_enable_axi_clk(host);
> +
> /* update on next VSYNC */
> writel(fb_info->fix.smem_start + offset,
> host->base + host->devdata->next_buf);
>
> + if (!host->enabled)
> + mxsfb_disable_axi_clk(host);
> +
> return 0;
> }
>
> @@ -608,13 +631,17 @@ static int mxsfb_restore_mode(struct mxsfb_info *host,
> unsigned line_count;
> unsigned period;
> unsigned long pa, fbsize;
> - int bits_per_pixel, ofs;
> + int bits_per_pixel, ofs, ret = 0;
> u32 transfer_count, vdctrl0, vdctrl2, vdctrl3, vdctrl4, ctrl;
>
> + mxsfb_enable_axi_clk(host);
> +
> /* Only restore the mode when the controller is running */
> ctrl = readl(host->base + LCDC_CTRL);
> - if (!(ctrl & CTRL_RUN))
> - return -EINVAL;
> + if (!(ctrl & CTRL_RUN)) {
> + ret = -EINVAL;
> + goto err;
> + }
>
> vdctrl0 = readl(host->base + LCDC_VDCTRL0);
> vdctrl2 = readl(host->base + LCDC_VDCTRL2);
> @@ -635,7 +662,8 @@ static int mxsfb_restore_mode(struct mxsfb_info *host,
> break;
> case 1:
> default:
> - return -EINVAL;
> + ret = -EINVAL;
> + goto err;
> }
>
> fb_info->var.bits_per_pixel = bits_per_pixel;
> @@ -673,10 +701,14 @@ static int mxsfb_restore_mode(struct mxsfb_info *host,
>
> pa = readl(host->base + host->devdata->cur_buf);
> fbsize = fb_info->fix.line_length * vmode->yres;
> - if (pa < fb_info->fix.smem_start)
> - return -EINVAL;
> - if (pa + fbsize > fb_info->fix.smem_start + fb_info->fix.smem_len)
> - return -EINVAL;
> + if (pa < fb_info->fix.smem_start) {
> + ret = -EINVAL;
> + goto err;
> + }
> + if (pa + fbsize > fb_info->fix.smem_start + fb_info->fix.smem_len) {
> + ret = -EINVAL;
> + goto err;
> + }
> ofs = pa - fb_info->fix.smem_start;
> if (ofs) {
> memmove(fb_info->screen_base, fb_info->screen_base + ofs, fbsize);
> @@ -689,7 +721,11 @@ static int mxsfb_restore_mode(struct mxsfb_info *host,
> clk_prepare_enable(host->clk);
> host->enabled = 1;
>
> - return 0;
> +err:
> + if (ret)
> + mxsfb_disable_axi_clk(host);
> +
> + return ret;
> }
>
> static int mxsfb_init_fbinfo_dt(struct mxsfb_info *host,
> @@ -915,7 +951,9 @@ static int mxsfb_probe(struct platform_device *pdev)
> }
>
> if (!host->enabled) {
> + mxsfb_enable_axi_clk(host);
> writel(0, host->base + LCDC_CTRL);
> + mxsfb_disable_axi_clk(host);
> mxsfb_set_par(fb_info);
> mxsfb_enable_controller(fb_info);
> }
> @@ -954,11 +992,15 @@ static void mxsfb_shutdown(struct platform_device *pdev)
> struct fb_info *fb_info = platform_get_drvdata(pdev);
> struct mxsfb_info *host = to_imxfb_host(fb_info);
>
> + mxsfb_enable_axi_clk(host);
> +
> /*
> * Force stop the LCD controller as keeping it running during reboot
> * might interfere with the BootROM's boot mode pads sampling.
> */
> writel(CTRL_RUN, host->base + LCDC_CTRL + REG_CLR);
> +
> + mxsfb_disable_axi_clk(host);
> }
>
> static struct platform_driver mxsfb_driver = {
> --
> 2.1.0
>

It fixed the system hang issue at yocto rootfs at imx6sx sdb
and imx6sl sdb boards.

Tested-by: Peter Chen <peter.chen@freescale.com>

--

Best Regards,
Peter Chen