Re: [PATCH v2 19/19] media: ti-vpe: cal: fix stop state timeout

[Benoit Parrot <bparrot@ti.com>]

Tomi,

Thanks for the patch.

On 3/19/20 2:50 AM, Tomi Valkeinen wrote:
> The stop-state timeout needs to be over 100us as per CSI spec. With the
> CAL fclk of 266 MHZ on DRA76, with the current value the driver uses,
> the timeout is 24us. Too small timeout will cause failure to enable the
> streaming.
> 
> Also, the fclk can be different on other SoCs, as is the case with AM65x
> where the fclk is 250 MHz.
> 
> This patch fixes the timeout by calculating it correctly based on the
> fclk rate.
> 

Isn't this in relation to the clock sourcing the PHY module which is fixed
at 96Mhz (LVDSRX_96M_GFCLK)?

Benoit

> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Tested-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  drivers/media/platform/ti-vpe/cal.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
> index 0f90078ee8c2..d935c628597b 100644
> --- a/drivers/media/platform/ti-vpe/cal.c
> +++ b/drivers/media/platform/ti-vpe/cal.c
> @@ -6,6 +6,7 @@
>   * Benoit Parrot, <bparrot@ti.com>
>   */
>  
> +#include <linux/clk.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/ioctl.h>
> @@ -340,6 +341,7 @@ static const struct cal_data am654_cal_data = {
>   * all instances.
>   */
>  struct cal_dev {
> +	struct clk		*fclk;
>  	int			irq;
>  	void __iomem		*base;
>  	struct resource		*res;
> @@ -767,6 +769,7 @@ static void csi2_phy_config(struct cal_ctx *ctx);
>  static void csi2_phy_init(struct cal_ctx *ctx)
>  {
>  	u32 val;
> +	u32 sscounter;
>  
>  	/* Steps
>  	 *  1. Configure D-PHY mode and enable required lanes
> @@ -803,10 +806,20 @@ static void csi2_phy_init(struct cal_ctx *ctx)
>  	csi2_phy_config(ctx);
>  
>  	/* 3.B. Program Stop States */
> +	/*
> +	 * The stop-state-counter is based on fclk cycles, and we always use
> +	 * the x16 and x4 settings, so stop-state-timeout =
> +	 * fclk-cycle * 16 * 4 * counter.
> +	 *
> +	 * Stop-state-timeout must be more than 100us as per CSI2 spec, so we
> +	 * calculate a timeout that's 100us (rounding up).
> +	 */
> +	sscounter = DIV_ROUND_UP(clk_get_rate(ctx->dev->fclk), 10000 *  16 * 4);
> +
>  	val = reg_read(ctx->dev, CAL_CSI2_TIMING(ctx->csi2_port));
>  	set_field(&val, 1, CAL_CSI2_TIMING_STOP_STATE_X16_IO1_MASK);
> -	set_field(&val, 0, CAL_CSI2_TIMING_STOP_STATE_X4_IO1_MASK);
> -	set_field(&val, 407, CAL_CSI2_TIMING_STOP_STATE_COUNTER_IO1_MASK);
> +	set_field(&val, 1, CAL_CSI2_TIMING_STOP_STATE_X4_IO1_MASK);
> +	set_field(&val, sscounter, CAL_CSI2_TIMING_STOP_STATE_COUNTER_IO1_MASK);
>  	reg_write(ctx->dev, CAL_CSI2_TIMING(ctx->csi2_port), val);
>  	ctx_dbg(3, ctx, "CAL_CSI2_TIMING(%d) = 0x%08x Stop States\n",
>  		ctx->csi2_port,
> @@ -2257,6 +2270,12 @@ static int cal_probe(struct platform_device *pdev)
>  	/* save pdev pointer */
>  	dev->pdev = pdev;
>  
> +	dev->fclk = devm_clk_get(&pdev->dev, "fck");
> +	if (IS_ERR(dev->fclk)) {
> +		dev_err(&pdev->dev, "cannot get CAL fclk\n");
> +		return PTR_ERR(dev->fclk);
> +	}
> +
>  	syscon_camerrx = syscon_regmap_lookup_by_phandle(parent,
>  							 "ti,camerrx-control");
>  	ret = of_property_read_u32_index(parent, "ti,camerrx-control", 1,
>