Re: [PATCH 1/2] ARM: EXYNOS: Get current parent clock for power domain on/off

Javier Martinez Canillas
2015-04-02T12:29:41Z

Hello Krzysztof,

On 04/02/2015 10:06 AM, Krzysztof Kozlowski wrote:
> Using a fixed (by DTS) parent for clocks when turning on the power domain
> may introduce issues in other drivers. For example when such driver
> changes the parent during runtime and expects that he is the only place
> of such change.
>
> Do not rely entirely on DTS providing the fixed parent for such clocks.
> Instead if "pclkN" clock name is missing, grab a current parent of clock
> with clk_get_parent().
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> ---
> Documentation/devicetree/bindings/arm/exynos/power_domain.txt | 8 +++++---
> arch/arm/mach-exynos/pm_domains.c | 9 ++++++---
> 2 files changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/arm/exynos/power_domain.txt b/Documentation/devicetree/bindings/arm/exynos/power_domain.txt
> index 5da38c5ed476..0fc1312f6fd5 100644
> --- a/Documentation/devicetree/bindings/arm/exynos/power_domain.txt
> +++ b/Documentation/devicetree/bindings/arm/exynos/power_domain.txt
> @@ -19,9 +19,11 @@ Optional Properties:
> domains.
> - clock-names: The following clocks can be specified:
> - oscclk: Oscillator clock.
> - - pclkN, clkN: Pairs of parent of input clock and input clock to the
> - devices in this power domain. Maximum of 4 pairs (N = 0 to 3)
> - are supported currently.
> + - pclkN, clkN: Input clocks (clkN) to the devices in this power domain.
> + Optionally with parrents (pclkN). If such parent is provided
> + it will be used for reparenting the given clock when domain
> + is turned on. Otherwise the parent before power down will be
> + used. Maximum of 4 pairs (N = 0 to 3) are supported currently.
> - asbN: Clocks required by asynchronous bridges (ASB) present in
> the power domain. These clock should be enabled during power
> domain on/off operations.
> diff --git a/arch/arm/mach-exynos/pm_domains.c b/arch/arm/mach-exynos/pm_domains.c
> index cbe56b35aea0..c55bcf52a6ad 100644
> --- a/arch/arm/mach-exynos/pm_domains.c
> +++ b/arch/arm/mach-exynos/pm_domains.c
> @@ -37,6 +37,7 @@ struct exynos_pm_domain {
> struct clk *oscclk;
> struct clk *clk[MAX_CLK_PER_DOMAIN];
> struct clk *pclk[MAX_CLK_PER_DOMAIN];
> + unsigned int pclk_dynamic:MAX_CLK_PER_DOMAIN;
> struct clk *asb_clk[MAX_CLK_PER_DOMAIN];
> };
>
> @@ -62,6 +63,9 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
> for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
> if (IS_ERR(pd->clk[i]))
> break;
> + /* If parent was not set in DT, save current parent */
> + if (pd->pclk_dynamic & (1 << i))

Small nit: I personally think that using the BIT(i) macro for shifting bits
is more readable but I guess is a matter of personal taste.

> + pd->pclk[i] = clk_get_parent(pd->clk[i]);
> if (clk_set_parent(pd->clk[i], pd->oscclk))
> pr_err("%s: error setting oscclk as parent to clock %d\n",
> pd->name, i);
> @@ -164,9 +168,8 @@ static __init int exynos4_pm_init_power_domain(void)
> snprintf(clk_name, sizeof(clk_name), "pclk%d", i);
> pd->pclk[i] = clk_get(dev, clk_name);
> if (IS_ERR(pd->pclk[i])) {
> - clk_put(pd->clk[i]);
> - pd->clk[i] = ERR_PTR(-EINVAL);
> - break;
> + pd->pclk_dynamic |= (1 << i);
> + pd->pclk[i] = clk_get_parent(pd->clk[i]);
> }
> }
>
>

Patch looks good to me:

Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>

I tested $subject along with 2/2 on an Exynos5420 Peach Pit and I see
that display comes up correctly on boot. Also after disabling the display:

$ echo 1 > /sys/devices/platform/exynos-drm/graphics/fb0/blank

the DISP1 power domain is off in /sys/kernel/debug/pm_genpd/pm_genpd_summary
and after enabling it again with:

$ echo 0 > /sys/devices/platform/exynos-drm/graphics/fb0/blank

the DISP1 power domain is on again and the display is working correctly.

Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>

Best regards,
Javier