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Message-ID: <a19de8d5-2b01-cb62-38a2-b0732068025c@samsung.com>
Date: Fri, 28 Aug 2020 15:30:04 +0900
From: Hoegeun Kwon <hoegeun.kwon@...sung.com>
To: Stefan Wahren <stefan.wahren@...e.com>, nsaenzjulienne@...e.de,
eric@...olt.net, maxime@...no.tech
Cc: devicetree@...r.kernel.org, tim.gover@...pberrypi.com,
dave.stevenson@...pberrypi.com, sboyd@...nel.org,
mturquette@...libre.com, kdasu.kdev@...il.com,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-clk@...r.kernel.org, robh+dt@...nel.org,
bcm-kernel-feedback-list@...adcom.com,
linux-rpi-kernel@...ts.infradead.org, phil@...pberrypi.com,
linux-arm-kernel@...ts.infradead.org,
Hoegeun Kwon <hoegeun.kwon@...sung.com>
Subject: Re: [PATCH 3/3] drm/vc4: hdmi: Add pixel bvb clock control
On 8/27/20 6:49 PM, Stefan Wahren wrote:
> Am 27.08.20 um 06:35 schrieb Hoegeun Kwon:
>> Hi Stefan,
>>
>> Thank you for your review.
>>
>>
>> On 8/26/20 7:04 PM, Stefan Wahren wrote:
>>> Hi Hoeguen,
>>>
>>> Am 21.08.20 um 09:10 schrieb Hoegeun Kwon:
>>>> 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.
>>> this patch introduces a mandatory clock, please update
>>> brcm,bcm2835-hdmi.yaml first.
>>>
>>> Is this clock physically available on BCM283x or only on BCM2711?
>> As far as I know, BCM2711 raspberry pi 4 supports 4k,
>>
>> don't supported on pi 3 and pi 3+.
>>
>> Since 4k is not supported in versions prior to Raspberry Pi 4,
>>
>> I don't think we need to modify the bvb clock.
>>
>>
>> So I think it is better to update 'brcm,bcm2711-hdmi.yaml'
>>
>> instead of 'brcm,bcm2835-hdmi.yaml'.
> You are correct please update only brcm,bcm2711-hdmi.yaml.
>
> My concern was that the function vc4_hdmi_encoder_pre_crtc_configure()
> is called on a non-bcm2711 platform or on a Raspberry Pi 4 with an older
> DTB. So making the BVB clock optional might be better?
You are right, if use old dtb, we have a problem with the hdmi driver.
So how about modifying it like this?
@@ -1614,8 +1614,8 @@ static int vc5_hdmi_init_resources(struct vc4_hdmi
*vc4_hdmi)
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);
+ DRM_WARN("Failed to get pixel bvb clock\n");
+ vc4_hdmi->pixel_bvb_clock = NULL;
}
vc4_hdmi->reset = devm_reset_control_get(dev, NULL);
If we modify like this, if there is no bvb clock in dtb, then
pixel_bvb_clock will be null
and it will not affect the clk control function below.
- clk_set_rate()
- clk_prepare_enable()
- clk_disable_unprepare()
Best regards
Hoegeun
>
>> Please comment, what do you think?
>>
>>> I'm a little bit afraid, this change could break with older firmware
>>> versions on BCM283x.
>> Tested it several times with libdrm modetest.
>>
>> I expect there will be no problem.
>>
>>
>> Best regards,
>>
>> Hoegeun
>>
>>> Best regards
>>> Stefan
>>>
>>>> Signed-off-by: Hoegeun Kwon <hoegeun.kwon@...sung.com>
>>>> ---
>>>> 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 40000
>>>> +#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 ? 150000000 : 75000000));
>>>> + 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;
>>>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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