linux-kernel - Re: [PATCH 2/4] drm/bridge: add Microchip DSI controller support for sam9x7 SoC series

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Message-ID: <597d49f6-7b25-434f-b14d-17ce17abb212@microchip.com>
Date: Thu, 11 Jul 2024 10:08:03 +0000
From: <Manikandan.M@...rochip.com>
To: <conor@...nel.org>, <krzk@...nel.org>
CC: <Hari.PrasathGE@...rochip.com>, <andrzej.hajda@...el.com>,
	<neil.armstrong@...aro.org>, <rfoss@...nel.org>,
	<Laurent.pinchart@...asonboard.com>, <jonas@...boo.se>,
	<jernej.skrabec@...il.com>, <airlied@...il.com>, <daniel@...ll.ch>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <robh@...nel.org>, <krzk+dt@...nel.org>,
	<conor+dt@...nel.org>, <linux@...linux.org.uk>,
	<Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
	<claudiu.beznea@...on.dev>, <arnd@...db.de>, <Jason@...c4.com>,
	<palmer@...osinc.com>, <mpe@...erman.id.au>, <rdunlap@...radead.org>,
	<dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/4] drm/bridge: add Microchip DSI controller support for
 sam9x7 SoC series

On 11/07/24 3:28 pm, Conor Dooley wrote:
> On Thu, Jul 11, 2024 at 11:05:37AM +0200, Krzysztof Kozlowski wrote:
>> On 11/07/2024 10:30,Manikandan.M@...rochip.com  wrote:
>>> Hi Krzysztof,
>>>
>>> On 04/07/24 4:27 pm, Krzysztof Kozlowski wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> On 04/07/2024 10:48, Manikandan Muralidharan wrote:
>>>>> Add the Microchip's DSI controller wrapper driver that uses
>>>>> the Synopsys DesignWare MIPI DSI host controller bridge.
>>>>>
>>>>> Signed-off-by: Manikandan Muralidharan<manikandan.m@...rochip.com>
>>>>> ---
>>>>
>>>> ...
>>>>
>>>>> +
>>>>> +#define HSTT(_maxfreq, _c_lp2hs, _c_hs2lp, _d_lp2hs, _d_hs2lp)       \
>>>>> +{                                    \
>>>>> +     .maxfreq = _maxfreq,            \
>>>>> +     .timing = {                     \
>>>>> +             .clk_lp2hs = _c_lp2hs,  \
>>>>> +             .clk_hs2lp = _c_hs2lp,  \
>>>>> +             .data_lp2hs = _d_lp2hs, \
>>>>> +             .data_hs2lp = _d_hs2lp, \
>>>>> +     }                               \
>>>>> +}
>>>>> +
>>>>> +struct hstt hstt_table[] = {
>>>> So more globals? No.
>>> In the sam9x7 datasheet, the high speed transition time for data and
>>> clock lane at different freq for the DSI controller ranges are tabulated
>>> with constant values.
>>> I referred other similar platforms for the functionality and found
>>> similar way of implementation,  only a few had equations to derive the
>>> low power and high speed timings.I am not able to come up with a more
>>> efficient method. If there is something I am missing, please suggest.
>>> TIA
>> Yeah, this should not be a global. Nothing above suggests it.
> I think what Krzysztof is suggesting here is use of the static
> keyword...
Yes, after looking at the implementation in similar platforms, I did 
find out.
Thank you Conor.
> 
>> BTW, no W=1 clang warnings? Are you sure?
>>
>> Best regards,
>> Krzysztof

-- 
Thanks and Regards,
Manikandan M.