linux-kernel - Re: [EXT] Re: [PATCH] media: imx-jpeg: Leave a blank space before the configuration data

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Date:   Fri, 27 May 2022 12:05:53 +0200
From:   Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
To:     Ming Qian <ming.qian@....com>
Cc:     "mchehab@...nel.org" <mchehab@...nel.org>,
        "Mirela Rabulea (OSS)" <mirela.rabulea@....nxp.com>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXT] Re: [PATCH] media: imx-jpeg: Leave a blank space before
 the configuration data

On Fri, May 27, 2022 at 09:52:48AM +0000, Ming Qian wrote:
> > From: Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
> > Sent: 2022年5月27日 17:38
> > To: Ming Qian <ming.qian@....com>
> > Cc: mchehab@...nel.org; Mirela Rabulea (OSS)
> > <mirela.rabulea@....nxp.com>; hverkuil-cisco@...all.nl;
> > shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> > festevam@...il.com; dl-linux-imx <linux-imx@....com>;
> > linux-media@...r.kernel.org; linux-kernel@...r.kernel.org;
> > devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
> > Subject: [EXT] Re: [PATCH] media: imx-jpeg: Leave a blank space before the
> > configuration data
> > 
> > Caution: EXT Email
> > 
> > Hi Ming,
> > I think have some comments on the code for this would be nice for the future
> > 
> > On Fri, May 27, 2022 at 03:54:35PM +0800, Ming Qian wrote:
> > > There is a hardware bug that it will load the first 128 bytes of
> > > configuration data twice, it will led to some configure error.
> > > so shift the configuration data 128 bytes, and make the first 128
> > > bytes all zero, then hardware will load the 128 zero twice,
> > 
> > From what I've understood you initialize cfg_stm with zeros then you start to
> > write the configuration from 0x80 (128 bytes), avoiding the hw issue right?
> > 
> 

Hi Ming,

> HI Tommaso,
>     Yes, you're right, there is a hardware bug.
> I want to write the configuration data from the offset 0x80,
> And set the first 128 bytes to zero.
> Then the hardware bug can be avoided.

Thanks for your clarification!
Unfortunately I can't test this on a real board but the implementation looks
good to me. Only thing is missing I think we need some notes to keep
track of this known issue (for the sake of clarity just a note on why we
start to write from 0x80)

Reviewed-by: Tommaso Merciai <tommaso.merciai@...rulasolutions.com>

Thanks,
Tommaso

> 
> Ming.
> 
> 
> > > and ignore them as garbage.
> > > then the configuration data can be loaded correctly
> > >
> > > Signed-off-by: Ming Qian <ming.qian@....com>
> > > Reviewed-by: Mirela Rabulea <mirela.rabulea@....com>
> > > ---
> > >  drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > > b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > > index 734e1b65fbc7..ad4213e020f3 100644
> > > --- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > > +++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
> > > @@ -519,6 +519,7 @@ static bool mxc_jpeg_alloc_slot_data(struct
> > mxc_jpeg_dev *jpeg,
> > >                                    GFP_ATOMIC);
> > >       if (!cfg_stm)
> > >               goto err;
> > > +     memset(cfg_stm, 0, MXC_JPEG_MAX_CFG_STREAM);
> > >       jpeg->slot_data[slot].cfg_stream_vaddr = cfg_stm;
> > >
> > >  skip_alloc:
> > > @@ -755,7 +756,7 @@ static unsigned int mxc_jpeg_setup_cfg_stream(void
> > *cfg_stream_vaddr,
> > >                                             u32 fourcc,
> > >                                             u16 w, u16 h)  {
> > > -     unsigned int offset = 0;
> > > +     unsigned int offset = 0x80;
> > >       u8 *cfg = (u8 *)cfg_stream_vaddr;
> > >       struct mxc_jpeg_sof *sof;
> > >       struct mxc_jpeg_sos *sos;
> > > --
> > > 2.36.1
> > >
> > 
> > Thanks,
> > Tommaso
> > 
> > --
> > Tommaso Merciai
> > Embedded Linux Engineer
> > tommaso.merciai@...rulasolutions.com
> > __________________________________
> > 
> > Amarula Solutions SRL
> > Via Le Canevare 30, 31100 Treviso, Veneto, IT T. +39 042 243 5310
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-- 
Tommaso Merciai
Embedded Linux Engineer
tommaso.merciai@...rulasolutions.com
__________________________________

Amarula Solutions SRL
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