Re: [PATCH] drm/tegra: gr2d: Explicitly control module reset

[Dmitry Osipenko <digetx@gmail.com>]

08.07.2021 17:37, Thierry Reding пишет:
> From: Thierry Reding <treding@nvidia.com>
> 
> As of commit 4782c0a5dd88 ("clk: tegra: Don't deassert reset on enabling
> clocks"), module resets are no longer automatically deasserted when the
> module clock is enabled. To make sure that the gr2d module continues to
> work, we need to explicitly control the module reset.
> 
> Fixes: 4782c0a5dd88 ("clk: tegra: Don't deassert reset on enabling clocks")
> Signed-off-by: Thierry Reding <treding@nvidia.com>

On which board do see this problem?

TRM says that 2d should be in reset by default, but somehow it's not a
problem on devices that use fastboot.. why would it touch the 2d reset?

> ---
>  drivers/gpu/drm/tegra/gr2d.c | 33 +++++++++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tegra/gr2d.c b/drivers/gpu/drm/tegra/gr2d.c
> index de288cba3905..ba3722f1b865 100644
> --- a/drivers/gpu/drm/tegra/gr2d.c
> +++ b/drivers/gpu/drm/tegra/gr2d.c
> @@ -4,9 +4,11 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/delay.h>
>  #include <linux/iommu.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
> +#include <linux/reset.h>
>  
>  #include "drm.h"
>  #include "gem.h"
> @@ -19,6 +21,7 @@ struct gr2d_soc {
>  struct gr2d {
>  	struct tegra_drm_client client;
>  	struct host1x_channel *channel;
> +	struct reset_control *rst;

Unused variable?

>  	struct clk *clk;
>  
>  	const struct gr2d_soc *soc;
> @@ -208,6 +211,12 @@ static int gr2d_probe(struct platform_device *pdev)
>  	if (!syncpts)
>  		return -ENOMEM;
>  
> +	gr2d->rst = devm_reset_control_get(dev, NULL);
> +	if (IS_ERR(gr2d->rst)) {
> +		dev_err(dev, "cannot get reset\n");
> +		return PTR_ERR(gr2d->rst);
> +	}
> +
>  	gr2d->clk = devm_clk_get(dev, NULL);
>  	if (IS_ERR(gr2d->clk)) {
>  		dev_err(dev, "cannot get clock\n");
> @@ -220,6 +229,14 @@ static int gr2d_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> +	usleep_range(2000, 4000);
> +
> +	err = reset_control_deassert(gr2d->rst);
> +	if (err < 0) {
> +		dev_err(dev, "failed to deassert reset: %d\n", err);
> +		goto disable_clk;
> +	}
> +
>  	INIT_LIST_HEAD(&gr2d->client.base.list);
>  	gr2d->client.base.ops = &gr2d_client_ops;
>  	gr2d->client.base.dev = dev;
> @@ -234,8 +251,7 @@ static int gr2d_probe(struct platform_device *pdev)
>  	err = host1x_client_register(&gr2d->client.base);
>  	if (err < 0) {
>  		dev_err(dev, "failed to register host1x client: %d\n", err);
> -		clk_disable_unprepare(gr2d->clk);
> -		return err;
> +		goto assert_rst;
>  	}
>  
>  	/* initialize address register map */
> @@ -245,6 +261,13 @@ static int gr2d_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, gr2d);
>  
>  	return 0;
> +
> +assert_rst:
> +	(void)reset_control_assert(gr2d->rst);

(void)?