drm/dbi: Print errors for mipi_dbi_command()

The macro mipi_dbi_command() does not report errors unless you wrap it
in another macro to do the error reporting.

Report a rate-limited error so we know what is going on.

Drop the only user in DRM using mipi_dbi_command() and actually checking
the error explicitly, let it use mipi_dbi_command_buf() directly
instead.

After this any code wishing to send command arrays can rely on
mipi_dbi_command() providing an appropriate error message if something
goes wrong.

Suggested-by: Noralf Trønnes <noralf@tronnes.org>
Suggested-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpu/drm/drm_mipi_dbi.c

@@ -645,7 +645,7 @@ static int mipi_dbi_poweron_reset_conditional(struct mipi_dbi_dev *dbidev, bool
 		return 1;
 
 	mipi_dbi_hw_reset(dbi);
-	ret = mipi_dbi_command(dbi, MIPI_DCS_SOFT_RESET);
+	ret = mipi_dbi_command_buf(dbi, MIPI_DCS_SOFT_RESET, NULL, 0);
 	if (ret) {
 		DRM_DEV_ERROR(dev, "Failed to send reset command (%d)\n", ret);
 		if (dbidev->regulator)

include/drm/drm_mipi_dbi.h

@@ -183,7 +183,11 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
 #define mipi_dbi_command(dbi, cmd, seq...) \
 ({ \
 	const u8 d[] = { seq }; \
-	mipi_dbi_command_stackbuf(dbi, cmd, d, ARRAY_SIZE(d)); \
+	struct device *dev = &dbi->spi->dev; \
+	int ret; \
+	ret = mipi_dbi_command_stackbuf(dbi, cmd, d, ARRAY_SIZE(d)); \
+	if (ret) \
+		dev_err_ratelimited(dev, "error %d when sending command\n", ret); \
 })
 
 #ifdef CONFIG_DEBUG_FS