Patch "drm: bridge: samsung-dsim: Fix waiting for empty cmd transfer FIFO on older Exynos" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm: bridge: samsung-dsim: Fix waiting for empty cmd transfer FIFO on older Exynos

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-bridge-samsung-dsim-fix-waiting-for-empty-cmd-tr.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit eca802c18a8f28b2202d97ffb996ae05bbb176ad
Author: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Date:   Wed Aug 9 16:56:41 2023 +0200

    drm: bridge: samsung-dsim: Fix waiting for empty cmd transfer FIFO on older Exynos
    
    [ Upstream commit 15f389da11257b806da75a070cfa41ca0cc15aae ]
    
    Samsung DSIM used in older Exynos SoCs (like Exynos 4210, 4x12, 3250)
    doesn't report empty level of packer header FIFO. In case of those SoCs,
    use the old way of waiting for empty command tranfsfer FIFO, removed
    recently by commit 14806c641582 ("drm: bridge: samsung-dsim: Drain command transfer FIFO before transfer").
    
    Fixes: 14806c641582 ("drm: bridge: samsung-dsim: Drain command transfer FIFO before transfer")
    Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
    Reviewed-by: Marek Vasut <marex@xxxxxxx>
    Signed-off-by: Robert Foss <rfoss@xxxxxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/20230809145641.3213210-1-m.szyprowski@xxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 6f2ca74238d14..19bdb32dbc9aa 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -413,6 +413,7 @@ static const struct samsung_dsim_driver_data exynos3_dsi_driver_data = {
 	.m_min = 41,
 	.m_max = 125,
 	.min_freq = 500,
+	.has_broken_fifoctrl_emptyhdr = 1,
 };
 
 static const struct samsung_dsim_driver_data exynos4_dsi_driver_data = {
@@ -429,6 +430,7 @@ static const struct samsung_dsim_driver_data exynos4_dsi_driver_data = {
 	.m_min = 41,
 	.m_max = 125,
 	.min_freq = 500,
+	.has_broken_fifoctrl_emptyhdr = 1,
 };
 
 static const struct samsung_dsim_driver_data exynos5_dsi_driver_data = {
@@ -1010,8 +1012,20 @@ static int samsung_dsim_wait_for_hdr_fifo(struct samsung_dsim *dsi)
 	do {
 		u32 reg = samsung_dsim_read(dsi, DSIM_FIFOCTRL_REG);
 
-		if (reg & DSIM_SFR_HEADER_EMPTY)
-			return 0;
+		if (!dsi->driver_data->has_broken_fifoctrl_emptyhdr) {
+			if (reg & DSIM_SFR_HEADER_EMPTY)
+				return 0;
+		} else {
+			if (!(reg & DSIM_SFR_HEADER_FULL)) {
+				/*
+				 * Wait a little bit, so the pending data can
+				 * actually leave the FIFO to avoid overflow.
+				 */
+				if (!cond_resched())
+					usleep_range(950, 1050);
+				return 0;
+			}
+		}
 
 		if (!cond_resched())
 			usleep_range(950, 1050);
diff --git a/include/drm/bridge/samsung-dsim.h b/include/drm/bridge/samsung-dsim.h
index 05100e91ecb96..6fc9bb2979e45 100644
--- a/include/drm/bridge/samsung-dsim.h
+++ b/include/drm/bridge/samsung-dsim.h
@@ -53,6 +53,7 @@ struct samsung_dsim_driver_data {
 	unsigned int plltmr_reg;
 	unsigned int has_freqband:1;
 	unsigned int has_clklane_stop:1;
+	unsigned int has_broken_fifoctrl_emptyhdr:1;
 	unsigned int num_clks;
 	unsigned int min_freq;
 	unsigned int max_freq;