[PATCH RFC 5/5] drm/msm/dsi: Use MSM and DRM DSC helper methods

Fri Mar 31 01:31:11 UTC 2023

On 3/30/2023 6:25 PM, Dmitry Baryshkov wrote:
> On 31/03/2023 04:12, Jessica Zhang wrote:
>>
>>
>> On 3/30/2023 5:16 PM, Dmitry Baryshkov wrote:
>>> On Fri, 31 Mar 2023 at 03:07, Jessica Zhang 
>>> <quic_jesszhan at quicinc.com> wrote:
>>>>
>>>>
>>>>
>>>> On 3/30/2023 4:14 PM, Dmitry Baryshkov wrote:
>>>>> On 31/03/2023 01:49, Jessica Zhang wrote:
>>>>>>
>>>>>>
>>>>>> On 3/29/2023 4:48 PM, Dmitry Baryshkov wrote:
>>>>>>> On 30/03/2023 02:18, Jessica Zhang wrote:
>>>>>>>> Use MSM and DRM DSC helper methods.
>>>>>>>>
>>>>>>>> Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.com>
>>>>>>>> ---
>>>>>>>>    drivers/gpu/drm/msm/dsi/dsi_host.c | 18 ++++++++++++------
>>>>>>>>    1 file changed, 12 insertions(+), 6 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>>>>>> b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>>>>>> index 74d38f90398a..7419fe58a941 100644
>>>>>>>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>>>>>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>>>>>>> @@ -31,6 +31,7 @@
>>>>>>>>    #include "msm_kms.h"
>>>>>>>>    #include "msm_gem.h"
>>>>>>>>    #include "phy/dsi_phy.h"
>>>>>>>> +#include "disp/msm_dsc_helper.h"
>>>>>>>>    #define DSI_RESET_TOGGLE_DELAY_MS 20
>>>>>>>> @@ -841,14 +842,14 @@ static void dsi_update_dsc_timing(struct
>>>>>>>> msm_dsi_host *msm_host, bool is_cmd_mod
>>>>>>>>    {
>>>>>>>>        struct drm_dsc_config *dsc = msm_host->dsc;
>>>>>>>>        u32 reg, reg_ctrl, reg_ctrl2;
>>>>>>>> -    u32 slice_per_intf, total_bytes_per_intf;
>>>>>>>> +    u32 slice_per_intf;
>>>>>>>>        u32 pkt_per_line;
>>>>>>>>        u32 eol_byte_num;
>>>>>>>>        /* first calculate dsc parameters and then program
>>>>>>>>         * compress mode registers
>>>>>>>>         */
>>>>>>>> -    slice_per_intf = DIV_ROUND_UP(hdisplay, dsc->slice_width);
>>>>>>>> +    slice_per_intf = msm_dsc_get_slice_per_intf(dsc, hdisplay);
>>>>>>>
>>>>>>> This looks good
>>>>>>>
>>>>>>>>        /*
>>>>>>>>         * If slice_count is greater than slice_per_intf
>>>>>>>> @@ -858,10 +859,10 @@ static void dsi_update_dsc_timing(struct
>>>>>>>> msm_dsi_host *msm_host, bool is_cmd_mod
>>>>>>>>        if (dsc->slice_count > slice_per_intf)
>>>>>>>>            dsc->slice_count = 1;
>>>>>>>> -    total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;
>>>>>>>> +    eol_byte_num = msm_dsc_get_eol_byte_num(msm_host->dsc, 
>>>>>>>> hdisplay,
>>>>>>>> +            dsi_get_bpp(msm_host->format));
>>>>>>>> -    eol_byte_num = total_bytes_per_intf % 3;
>>>>>>>> -    pkt_per_line = slice_per_intf / dsc->slice_count;
>>>>>>>> +    pkt_per_line = slice_per_intf / MSM_DSC_SLICE_PER_PKT;
>>>>>>>
>>>>>>> And for these values the result is definitely changed. Separate 
>>>>>>> patch
>>>>>>> & description please. Just in case, "values per downstream 
>>>>>>> kernel" is
>>>>>>> not a proper description for such changes.
>>>>>>
>>>>>> Hi Dmitry,
>>>>>>
>>>>>> Sure, I can put this into a separate patch.
>>>>>>
>>>>>> The reason this was changed from slice_count to SLICE_PER_PKT was
>>>>>> because slice count and slice per packet aren't always equivalent.
>>>>>> There can be cases where panel configures DSC to have multiple soft
>>>>>> slices per interface, but the panel only specifies 1 slice per 
>>>>>> packet.
>>>>>
>>>>> Please put this nice description into the commit message. It is 
>>>>> exactly
>>>>> what I was looking for!
>>>>>
>>>>> BTW: Do you expect to change MSM_DSC_SLICE_PER_PKT later or it will 
>>>>> stay
>>>>> at "1"? If so, it might be easier to drop it and instead add a 
>>>>> comment.
>>>>
>>>> MSM_DSC_SLICE_PER_PKT is the default value for panels that don't 
>>>> specify
>>>> a slice_per_pkt value. (Now that I think about it, might be better to
>>>> call it MSM_DSC_DEFAULT_SLICE_PER_PKT instead...)
>>>
>>> Note, there is no slice_per_pkt in drm_dsc_config, so we must come up
>>> with another way to pass this data from the panel or to deduce the
>>> value in our driver.
>>
>> AFAIK we aren't developing on any panels that have a non-default 
>> slice-per-packet count right now, so I'm not sure if it would be worth 
>> the effort to add this if there's no panel we can validate it on.
>>
>> FWIW, downstream reads slice_per_pkt from a custom DT entry [1]
> 
> As you might guess, this approach is frowned upon in upstream kernel. 
> This info should come from panel (e.g. extend drm_dsc_config or deduce 
> the value in msm driver).
> 

Yes, I am already aware slice_per_pkt should come from the panel 
otherwise defaults to 1. Today MSM driver or even drm_panels for that 
matter dont support passing this.

We can extend adding it to the drm_panel and coming from there in 
another series. Let this series first add the support for DSC 1.2 for 
existing DSC 1.1 configurations. Even DSC 1.1 doesnt use custom 
slice_per_pkt today. So nothing broken.

>>
>> [1] 
>> https://android.googlesource.com/kernel/msm-extra/devicetree/+/refs/heads/android-msm-bramble-4.19-android11-qpr1/qcom/dsi-panel-r66451-dsc-fhd-plus-120hz-cmd.dtsi#115 
>>
>>
>>>
>>>>
>>>> I don't expect it to change in the future, but it's a little more
>>>> readable than just dividing by 1 IMO. If you prefer dropping the macro
>>>> and adding a comment, I'm also okay with that.
>>>
>>> There is no need to divide by 1, the value doesn't change. So I'd
>>> probably prefer something like:
>>>
>>> /* Default to 1 slice per packet */
>>> if (panel_slice_per_pkt)
>>>      pkt_per_line = slice_per_intf / panel_slice_per_pkt;
>>> else
>>>      pkt_per_line = slice_per_intf;
>>>
>>> Or:
>>>
>>> /* Default to 1 slice per packet */
>>> slice_per_pkt = 1;
>>> if (panel_slice_per_pkt)
>>>      slice_per_pkt = panel_slice_per_pkt;
>>> pkt_per_line = slice_per_intf / slice_per_pkt;
>>
>> Acked.
>>
> 
> 