linux-kernel - Re: [PATCH v6 5/9] drm/meson: gate px

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Date:   Mon, 3 Jul 2023 09:24:23 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     George Stark <gnstark@...rdevices.ru>,
        Jerome Brunet <jbrunet@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Nicolas Belin <nbelin@...libre.com>
Cc:     linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v6 5/9] drm/meson: gate px_clk when setting rate

On 30/06/2023 20:10, George Stark wrote:
> Hello Neil
> 
> On 6/30/23 19:29, Neil Armstrong wrote:
>> Disable the px_clk when setting the rate to recover a fully
>> configured and correctly reset VCLK clock tree after the rate
>> is set.
>>
>> Fixes: 77d9e1e6b846 ("drm/meson: add support for MIPI-DSI transceiver")
>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>> ---
>>   drivers/gpu/drm/meson/meson_dw_mipi_dsi.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/meson/meson_dw_mipi_dsi.c b/drivers/gpu/drm/meson/meson_dw_mipi_dsi.c
>> index 57447abf1a29..dc63d2d813a9 100644
>> --- a/drivers/gpu/drm/meson/meson_dw_mipi_dsi.c
>> +++ b/drivers/gpu/drm/meson/meson_dw_mipi_dsi.c
>> @@ -94,6 +94,7 @@ static int dw_mipi_dsi_phy_init(void *priv_data)
>>           return ret;
>>       }
>> +    clk_disable_unprepare(mipi_dsi->px_clk);
>>       ret = clk_set_rate(mipi_dsi->px_clk, mipi_dsi->mode->clock * 1000);
>>       if (ret) {
>> @@ -102,6 +103,12 @@ static int dw_mipi_dsi_phy_init(void *priv_data)
>>           return ret;
>>       }
>> +    clk_prepare_enable(mipi_dsi->px_clk);
> probably should be:
> ret = clk_prepare_enable(mipi_dsi->px_clk);

Indeed, thx for noticing :-)

>> +    if (ret) {
>> +        dev_err(mipi_dsi->dev, "Failed to enable DSI Pixel clock (ret %d)\n", ret);
>> +        return ret;
>> +    }
>> +
>>       switch (mipi_dsi->dsi_device->format) {
>>       case MIPI_DSI_FMT_RGB888:
>>           dpi_data_format = DPI_COLOR_24BIT;
>>