Re: [PATCH v2 2/4] drm/vc4: hdmi: Add pixel bvb clock control
Hi Chanwoo,
On 9/1/20 1:27 PM, Chanwoo Choi wrote:
> Hi Hoegeun,
>
> It looks good to me. But, just one comment.
>
> On 9/1/20 1:07 PM, Hoegeun Kwon wrote:
>> There is a problem that the output does not work at a resolution
>> exceeding FHD. To solve this, we need to adjust the bvb clock at a
>> resolution exceeding FHD.
>>
>> Signed-off-by: Hoegeun Kwon
>> ---
>> drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +
>> drivers/gpu/drm/vc4/vc4_hdmi.h | 1 +
>> 2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> index 95ec5eedea39..eb3192d1fd86 100644
>> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
>> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
>> @@ -80,6 +80,7 @@
>> # define VC4_HD_M_ENABLE BIT(0)
>>
>> #define CEC_CLOCK_FREQ 4
>> +#define VC4_HSM_MID_CLOCK 149985000
>>
>> static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
>> {
>> @@ -380,6 +381,7 @@ static void vc4_hdmi_encoder_post_crtc_powerdown(struct
>> drm_encoder *encoder)
>> HDMI_WRITE(HDMI_VID_CTL,
>> HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
>>
>> +clk_disable_unprepare(vc4_hdmi->pixel_bvb_clock);
>> clk_disable_unprepare(vc4_hdmi->hsm_clock);
>> clk_disable_unprepare(vc4_hdmi->pixel_clock);
>>
>> @@ -638,6 +640,23 @@ static void vc4_hdmi_encoder_pre_crtc_configure(struct
>> drm_encoder *encoder)
>> return;
>> }
>>
>> +ret = clk_set_rate(vc4_hdmi->pixel_bvb_clock,
>> +(hsm_rate > VC4_HSM_MID_CLOCK ? 15000 : 7500));
>> +if (ret) {
>> +DRM_ERROR("Failed to set pixel bvb clock rate: %d\n", ret);
>> +clk_disable_unprepare(vc4_hdmi->hsm_clock);
>> +clk_disable_unprepare(vc4_hdmi->pixel_clock);
>> +return;
>> +}
>> +
>> +ret = clk_prepare_enable(vc4_hdmi->pixel_bvb_clock);
>> +if (ret) {
>> +DRM_ERROR("Failed to turn on pixel bvb clock: %d\n", ret);
>> +clk_disable_unprepare(vc4_hdmi->hsm_clock);
>> +clk_disable_unprepare(vc4_hdmi->pixel_clock);
>> +return;
>> +}
> Generally, enable the clock before using clk and then change the clock rate.
> I think that you better to change the order between clk_prepare_enable and
> clk_set_rate.
Thank you for your comment.
As Maxime answered in another patch [1], there is no clear rule of order
here.
[1] https://lkml.org/lkml/2020/9/1/327
Best regards,
Hoegeun
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Re: [PATCH v2 2/4] drm/vc4: hdmi: Add pixel bvb clock control
Hi Hoegeun,
It looks good to me. But, just one comment.
On 9/1/20 1:07 PM, Hoegeun Kwon wrote:
> There is a problem that the output does not work at a resolution
> exceeding FHD. To solve this, we need to adjust the bvb clock at a
> resolution exceeding FHD.
>
> Signed-off-by: Hoegeun Kwon
> ---
> drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +
> drivers/gpu/drm/vc4/vc4_hdmi.h | 1 +
> 2 files changed, 26 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 95ec5eedea39..eb3192d1fd86 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -80,6 +80,7 @@
> # define VC4_HD_M_ENABLE BIT(0)
>
> #define CEC_CLOCK_FREQ 4
> +#define VC4_HSM_MID_CLOCK 149985000
>
> static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
> {
> @@ -380,6 +381,7 @@ static void vc4_hdmi_encoder_post_crtc_powerdown(struct
> drm_encoder *encoder)
> HDMI_WRITE(HDMI_VID_CTL,
> HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
>
> + clk_disable_unprepare(vc4_hdmi->pixel_bvb_clock);
> clk_disable_unprepare(vc4_hdmi->hsm_clock);
> clk_disable_unprepare(vc4_hdmi->pixel_clock);
>
> @@ -638,6 +640,23 @@ static void vc4_hdmi_encoder_pre_crtc_configure(struct
> drm_encoder *encoder)
> return;
> }
>
> + ret = clk_set_rate(vc4_hdmi->pixel_bvb_clock,
> + (hsm_rate > VC4_HSM_MID_CLOCK ? 15000 : 7500));
> + if (ret) {
> + DRM_ERROR("Failed to set pixel bvb clock rate: %d\n", ret);
> + clk_disable_unprepare(vc4_hdmi->hsm_clock);
> + clk_disable_unprepare(vc4_hdmi->pixel_clock);
> + return;
> + }
> +
> + ret = clk_prepare_enable(vc4_hdmi->pixel_bvb_clock);
> + if (ret) {
> + DRM_ERROR("Failed to turn on pixel bvb clock: %d\n", ret);
> + clk_disable_unprepare(vc4_hdmi->hsm_clock);
> + clk_disable_unprepare(vc4_hdmi->pixel_clock);
> + return;
> + }
Generally, enable the clock before using clk and then change the clock rate.
I think that you better to change the order between clk_prepare_enable and
clk_set_rate.
> +
> if (vc4_hdmi->variant->reset)
> vc4_hdmi->variant->reset(vc4_hdmi);
>
> @@ -1593,6 +1612,12 @@ static int vc5_hdmi_init_resources(struct vc4_hdmi
> *vc4_hdmi)
> return PTR_ERR(vc4_hdmi->audio_clock);
> }
>
> + vc4_hdmi->pixel_bvb_clock = devm_clk_get(dev, "bvb");
> + if (IS_ERR(vc4_hdmi->pixel_bvb_clock)) {
> + DRM_ERROR("Failed to get pixel bvb clock\n");
> + return PTR_ERR(vc4_hdmi->pixel_bvb_clock);
> + }
> +
> vc4_hdmi->reset = devm_reset_control_get(dev, NULL);
> if (IS_ERR(vc4_hdmi->reset)) {
> DRM_ERROR("Failed to get HDMI reset line\n");
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> index 0806c6d9f24e..63c6f8bddf1d 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> @@ -147,6 +147,7 @@ struct vc4_hdmi {
> struct clk *pixel_clock;
> struct clk *hsm_clock;
> struct clk *audio_clock;
> + struct clk *pixel_bvb_clock;
>
> struct reset_control *reset;
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
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[PATCH v2 2/4] drm/vc4: hdmi: Add pixel bvb clock control
There is a problem that the output does not work at a resolution
exceeding FHD. To solve this, we need to adjust the bvb clock at a
resolution exceeding FHD.
Signed-off-by: Hoegeun Kwon
---
drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +
drivers/gpu/drm/vc4/vc4_hdmi.h | 1 +
2 files changed, 26 insertions(+)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 95ec5eedea39..eb3192d1fd86 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -80,6 +80,7 @@
# define VC4_HD_M_ENABLE BIT(0)
#define CEC_CLOCK_FREQ 4
+#define VC4_HSM_MID_CLOCK 149985000
static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
{
@@ -380,6 +381,7 @@ static void vc4_hdmi_encoder_post_crtc_powerdown(struct
drm_encoder *encoder)
HDMI_WRITE(HDMI_VID_CTL,
HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
+ clk_disable_unprepare(vc4_hdmi->pixel_bvb_clock);
clk_disable_unprepare(vc4_hdmi->hsm_clock);
clk_disable_unprepare(vc4_hdmi->pixel_clock);
@@ -638,6 +640,23 @@ static void vc4_hdmi_encoder_pre_crtc_configure(struct
drm_encoder *encoder)
return;
}
+ ret = clk_set_rate(vc4_hdmi->pixel_bvb_clock,
+ (hsm_rate > VC4_HSM_MID_CLOCK ? 15000 : 7500));
+ if (ret) {
+ DRM_ERROR("Failed to set pixel bvb clock rate: %d\n", ret);
+ clk_disable_unprepare(vc4_hdmi->hsm_clock);
+ clk_disable_unprepare(vc4_hdmi->pixel_clock);
+ return;
+ }
+
+ ret = clk_prepare_enable(vc4_hdmi->pixel_bvb_clock);
+ if (ret) {
+ DRM_ERROR("Failed to turn on pixel bvb clock: %d\n", ret);
+ clk_disable_unprepare(vc4_hdmi->hsm_clock);
+ clk_disable_unprepare(vc4_hdmi->pixel_clock);
+ return;
+ }
+
if (vc4_hdmi->variant->reset)
vc4_hdmi->variant->reset(vc4_hdmi);
@@ -1593,6 +1612,12 @@ static int vc5_hdmi_init_resources(struct vc4_hdmi
*vc4_hdmi)
return PTR_ERR(vc4_hdmi->audio_clock);
}
+ vc4_hdmi->pixel_bvb_clock = devm_clk_get(dev, "bvb");
+ if (IS_ERR(vc4_hdmi->pixel_bvb_clock)) {
+ DRM_ERROR("Failed to get pixel bvb clock\n");
+ return PTR_ERR(vc4_hdmi->pixel_bvb_clock);
+ }
+
vc4_hdmi->reset = devm_reset_control_get(dev, NULL);
if (IS_ERR(vc4_hdmi->reset)) {
DRM_ERROR("Failed to get HDMI reset line\n");
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
index 0806c6d9f24e..63c6f8bddf1d 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.h
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
@@ -147,6 +147,7 @@ struct vc4_hdmi {
struct clk *pixel_clock;
struct clk *hsm_clock;
struct clk *audio_clock;
+ struct clk *pixel_bvb_clock;
struct reset_control *reset;
--
2.17.1
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