The driver uses the upper-bound approach to decide the target JPEG
encode quality, but there's a logic bug that if the desired quality is
higher than what the driver can support, the driver falls back to using
the worst quality.

Fix the bug by assuming using the best quality in the beginning, and
with trivial refactor to avoid long lines.

Fixes: 45f13a57d813 ("media: platform: Add jpeg enc feature")
Signed-off-by: Fei Shao <fshao@chromium.org>
---

 drivers/media/platform/mediatek/jpeg/mtk_jpeg_enc_hw.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_enc_hw.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_enc_hw.c
index 2bbc48c7402c..f8fa3b841ccf 100644
--- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_enc_hw.c
+++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_enc_hw.c
@@ -127,6 +127,7 @@ void mtk_jpeg_set_enc_params(struct mtk_jpeg_ctx *ctx,  void __iomem *base)
 	u32 img_stride;
 	u32 mem_stride;
 	u32 i, enc_quality;
+	u32 nr_enc_quality = ARRAY_SIZE(mtk_jpeg_enc_quality);
 
 	value = width << 16 | height;
 	writel(value, base + JPEG_ENC_IMG_SIZE);
@@ -157,8 +158,8 @@ void mtk_jpeg_set_enc_params(struct mtk_jpeg_ctx *ctx,  void __iomem *base)
 	writel(img_stride, base + JPEG_ENC_IMG_STRIDE);
 	writel(mem_stride, base + JPEG_ENC_STRIDE);
 
-	enc_quality = mtk_jpeg_enc_quality[0].hardware_value;
-	for (i = 0; i < ARRAY_SIZE(mtk_jpeg_enc_quality); i++) {
+	enc_quality = mtk_jpeg_enc_quality[nr_enc_quality - 1].hardware_value;
+	for (i = 0; i < nr_enc_quality; i++) {
 		if (ctx->enc_quality <= mtk_jpeg_enc_quality[i].quality_param) {
 			enc_quality = mtk_jpeg_enc_quality[i].hardware_value;
 			break;
-- 
2.42.0.283.g2d96d420d3-goog

On Fri, Sep 8, 2023 at 9:29 PM Fei Shao <fshao@chromium.org> wrote:
>
> The driver uses the upper-bound approach to decide the target JPEG
> encode quality, but there's a logic bug that if the desired quality is
> higher than what the driver can support, the driver falls back to using
> the worst quality.
>
> Fix the bug by assuming using the best quality in the beginning, and
> with trivial refactor to avoid long lines.
>
> Fixes: 45f13a57d813 ("media: platform: Add jpeg enc feature")
> Signed-off-by: Fei Shao <fshao@chromium.org>

Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>