[PATCH RESEND] drm: mxsfb_crtc: Reset the eLCDIF controller

[Fabio Estevam]

On Mon, May 22, 2017 at 5:53 PM, Fabio Estevam <festevam at gmail.com> wrote:
> From: Fabio Estevam <fabio.estevam at nxp.com>
>
> According to the eLCDIF initialization steps listed in the MX6SX
> Reference Manual the eLCDIF block reset is mandatory.
>
> Without performing the eLCDIF reset the display shows garbage content
> when the kernel boots.
>
> In earlier tests this issue has not been observed because the bootloader
> was previously showing a splash screen and the bootloader display driver
> does properly implement the eLCDIF reset.
>
> Add the eLCDIF reset to the driver, so that it can operate correctly
> independently of the bootloader.
>
> Tested on a imx6sx-sdb board.
>
> Cc: <stable at vger.kernel.org> #4.11.x
> Signed-off-by: Fabio Estevam <fabio.estevam at nxp.com>
> Reviewed-by: Marek Vasut <marex at denx.de>
> ---
> Daniel,
>
> Marek suggested that this goes via drm-misc.

Sean/Jani/Daniel,

Any chance this could go via drm-misc?

Without this change the mxsfb driver is unusable on some platforms.

Thanks


>
> Thanks
>
>  drivers/gpu/drm/mxsfb/mxsfb_crtc.c | 42 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 42 insertions(+)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> index 1144e0c..0abe776 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> @@ -35,6 +35,13 @@
>  #include "mxsfb_drv.h"
>  #include "mxsfb_regs.h"
>
> +#define MXS_SET_ADDR           0x4
> +#define MXS_CLR_ADDR           0x8
> +#define MODULE_CLKGATE         BIT(30)
> +#define MODULE_SFTRST          BIT(31)
> +/* 1 second delay should be plenty of time for block reset */
> +#define RESET_TIMEOUT          1000000
> +
>  static u32 set_hsync_pulse_width(struct mxsfb_drm_private *mxsfb, u32 val)
>  {
>         return (val & mxsfb->devdata->hs_wdth_mask) <<
> @@ -159,6 +166,36 @@ static void mxsfb_disable_controller(struct mxsfb_drm_private *mxsfb)
>                 clk_disable_unprepare(mxsfb->clk_disp_axi);
>  }
>
> +/*
> + * Clear the bit and poll it cleared.  This is usually called with
> + * a reset address and mask being either SFTRST(bit 31) or CLKGATE
> + * (bit 30).
> + */
> +static int clear_poll_bit(void __iomem *addr, u32 mask)
> +{
> +       u32 reg;
> +
> +       writel(mask, addr + MXS_CLR_ADDR);
> +       return readl_poll_timeout(addr, reg, !(reg & mask), 0, RESET_TIMEOUT);
> +}
> +
> +static int mxsfb_reset_block(void __iomem *reset_addr)
> +{
> +       int ret;
> +
> +       ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
> +       if (ret)
> +               return ret;
> +
> +       writel(MODULE_CLKGATE, reset_addr + MXS_CLR_ADDR);
> +
> +       ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
> +       if (ret)
> +               return ret;
> +
> +       return clear_poll_bit(reset_addr, MODULE_CLKGATE);
> +}
> +
>  static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
>  {
>         struct drm_display_mode *m = &mxsfb->pipe.crtc.state->adjusted_mode;
> @@ -173,6 +210,11 @@ static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb)
>          */
>         mxsfb_enable_axi_clk(mxsfb);
>
> +       /* Mandatory eLCDIF reset as per the Reference Manual */
> +       err = mxsfb_reset_block(mxsfb->base);
> +       if (err)
> +               return;
> +
>         /* Clear the FIFOs */
>         writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_SET);
>
> --
> 2.7.4
>