On Thu, Jul 30, 2020 at 10:13:06AM +0200, Linus Walleij wrote:
> The vendor driver makes a few retries on read DSI
> transactions, something that is needed especially in
> case of read (such as reading the panel MTP ID) while
> the panel is running in video mode. This happens on
> the Samsung s6e63m0 panel on the Golden device.
>
So this fixes reads from the panel for samsung-golden?
> Retry reads and writes alike two times.
>
> Cc: Stephan Gerhold <stephan@xxxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> drivers/gpu/drm/mcde/mcde_dsi.c | 21 +++++++++++++++++++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/mcde/mcde_dsi.c b/drivers/gpu/drm/mcde/mcde_dsi.c
> index 337c4c5e3947..76fecd7ab658 100644
> --- a/drivers/gpu/drm/mcde/mcde_dsi.c
> +++ b/drivers/gpu/drm/mcde/mcde_dsi.c
> @@ -207,8 +207,8 @@ static int mcde_dsi_host_detach(struct mipi_dsi_host *host,
> (type == MIPI_DSI_GENERIC_READ_REQUEST_2_PARAM) || \
> (type == MIPI_DSI_DCS_READ))
>
> -static ssize_t mcde_dsi_host_transfer(struct mipi_dsi_host *host,
> - const struct mipi_dsi_msg *msg)
> +static ssize_t mcde_dsi_host_transfer_commit(struct mipi_dsi_host *host,
> + const struct mipi_dsi_msg *msg)
> {
> struct mcde_dsi *d = host_to_mcde_dsi(host);
> const u32 loop_delay_us = 10; /* us */
> @@ -353,6 +353,23 @@ static ssize_t mcde_dsi_host_transfer(struct mipi_dsi_host *host,
> return ret;
> }
>
> +static ssize_t mcde_dsi_host_transfer(struct mipi_dsi_host *host,
> + const struct mipi_dsi_msg *msg)
> +{
> + struct mcde_dsi *d = host_to_mcde_dsi(host);
> + int retries = 2;
> + ssize_t ret;
> +
> + while (retries--) {
> + ret = mcde_dsi_host_transfer_commit(host, msg);
> + if (ret >= 0)
> + return ret;
> + }
I wonder if it would be better to do this inside
mcde_dsi_host_transfer_commit() - it seems like the vendor driver only
retries triggering the command, i.e.
writel(~0, d->regs + DSI_DIRECT_CMD_STS_CLR);
writel(~0, d->regs + DSI_CMD_MODE_STS_CLR);
/* Send command */
writel(1, d->regs + DSI_DIRECT_CMD_SEND);
and does not write all the registers again.
> +
> + dev_err(d->dev, "gave up transfer after retrying\n");
> + return ret;
> +}
> +
> static const struct mipi_dsi_host_ops mcde_dsi_host_ops = {
> .attach = mcde_dsi_host_attach,
> .detach = mcde_dsi_host_detach,
> --
> 2.26.2
>
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