Re: [PATCH v6 07/10] drm/mediatek: add dsi transfer function

CK Hu
2016-08-11T07:10:21Z

Hi, YT:

On Wed, 2016-08-10 at 15:24 +0800, YT Shen wrote:
> Hi CK,
>
> On Fri, 2016-08-05 at 18:08 +0800, CK Hu wrote:
> > Hi, YT:
> >
> > On Thu, 2016-08-04 at 19:07 +0800, YT Shen wrote:
> > > From: shaoming chen <shaoming.chen@mediatek.com>
> > >
> > > add dsi read/write commands for transfer function
> > >
> > > Signed-off-by: shaoming chen <shaoming.chen@mediatek.com>
> > > ---
> > > drivers/gpu/drm/mediatek/mtk_dsi.c | 261 ++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 261 insertions(+)
> > >

[snip...]

> > > +
> > > +static void mtk_dsi_cmdq(struct mtk_dsi *dsi, const struct mipi_dsi_msg *msg)
> > > +{
> > > + const char *tx_buf = msg->tx_buf;
> > > + u32 reg_val, i;
> > > + u16 wc16;
> > > + u8 config, data0, data1, type;
> > > +
> > > + if (MTK_DSI_HOST_IS_READ(type)) {
> >
> > 'type' is used before assigned.
> Will fix.
>
> >
> > > + config = 4;
> > > + data0 = tx_buf[0];
> > > +
> > > + if (msg->rx_len < 3)
> > > + type = MIPI_DSI_DCS_READ;
> > > + else
> > > + type = MIPI_DSI_GENERIC_READ_REQUEST_1_PARAM;
> > > +
> > > + data1 = 0;
> > > + reg_val = (data1 << 24) | (data0 << 16) | (type << 8) | config;
> > > +
> > > + writel(reg_val, dsi->regs + DSI_CMDQ0);
> > > + mtk_dsi_mask(dsi, DSI_CMDQ_SIZE, CMDQ_SIZE, 1);
> >
> > I think this part looks like 'else' part. The difference is type and
> > config. I think type should be msg->type and you can independently set
> > BIT(2) of config.
> msg->type only tells about read or write, for the details we need to
> check other parameters. This part is for read, the else part is for
> write short packet. Not only BIT(2) of config is different, but also
> type and data1 is changed. Such a change would lead to difficult to
> understand.
>
> >
> > > + } else if (msg->tx_len > 2) { /* send long packet */
> > > + config = 2;
> > > + type = msg->type;
> > > + wc16 = msg->tx_len;
> > > +
> > > + reg_val = (wc16 << 16) | (type << 8) | config;
> > > +
> > > + writel(reg_val, dsi->regs + DSI_CMDQ0);
> > > +
> > > + for (i = 0; i < msg->tx_len; i++)
> > > + writeb(tx_buf[i], dsi->regs + DSI_CMDQ0 + 4 + i);
> > > +
> > > + mtk_dsi_mask(dsi, DSI_CMDQ_SIZE, CMDQ_SIZE,
> > > + 1 + (msg->tx_len + 3) / 4);
> > > + } else { /* send short packet */
> > > + config = 0;
> > > + data0 = tx_buf[0];
> > > +
> > > + if (msg->tx_len == 2) {
> > > + type = MIPI_DSI_DCS_SHORT_WRITE_PARAM;
> >
> > Why do you not set type as msg->type? This behavior looks like you
> > modify transfer type, but is this acceptable?
> msg->type only tells about read or write, for the details we need to
> check other parameters.

I think you could rewrite mtk_dsi_cmdq() as follow:

static void mtk_dsi_cmdq(struct mtk_dsi *dsi, const struct mipi_dsi_msg
*msg)
{
u32 i;
u32 src_off = (msg->tx_len > 2) ? 4 : 2;
u32 cmdq_size = (msg->tx_len > 2) ? 1 + (msg->tx_len + 3) / 4 : 1;
u32 config = (msg->tx_len > 2) ? BIT(1) : 0;
u32 type = msg->type;

if (MTK_DSI_HOST_IS_READ(type))
config |= BIT(2);

writel((type << 8) || config, dsi->regs + DSI_CMDQ0);
for (i = 0; i < msg->tx_len; i++)
writeb(msg->tx_buf[i], dsi->regs + DSI_CMDQ0 + src_off + i);
mtk_dsi_mask(dsi, DSI_CMDQ_SIZE, CMDQ_SIZE, cmdq_size);
}

If DSI HW does not support some type and it can be transferred to other
type, you could add a transfer function like this

static u8 mtk_dsi_map_to_supported_type(u8 type)
{
switch(type) {
case MIPI_DSI_DCS_SHORT_WRITE:
return MIPI_DSI_DCS_SHORT_WRITE_PARAM;
}

return type;
}

and then

u32 type = mtk_dsi_map_to_supported_type(msg->type);

>
> >
> > > + data1 = tx_buf[1];
> > > + } else {
> > > + type = MIPI_DSI_DCS_SHORT_WRITE;
> > > + data1 = 0;
> > > + }
> > > +
> > > + reg_val = (data1 << 24) | (data0 << 16) | (type << 8) | config;
> > > +
> > > + writel(reg_val, dsi->regs + DSI_CMDQ0);
> > > + mtk_dsi_mask(dsi, DSI_CMDQ_SIZE, CMDQ_SIZE, 1);
> > > + }
> > > +}
> > > +

[snip...]

> >
> > Regards,
> > CK
> >
>
>

Regards,
CK