[PATCH] mmc: sdhci-pci-gli: fix GL9750 DMA write corruption

[Matthew Schwartz <matthew.schwartz@linux.dev>]

The GL9750 SD host controller has intermittent data corruption during
DMA write operations. The GM_BURST register's R_OSRC_Lmt field
(bits 17:16), which limits outstanding DMA read requests from system
memory, is not being cleared during initialization. The Windows driver
sets R_OSRC_Lmt to zero, limiting requests to the smallest unit.

Clear R_OSRC_Lmt to match the Windows driver behavior. This eliminates
write corruption verified with f3write/f3read tests while maintaining
DMA performance.

Cc: stable@vger.kernel.org
Fixes: e51df6ce668a ("mmc: host: sdhci-pci: Add Genesys Logic GL975x support")
Closes: https://lore.kernel.org/linux-mmc/33d12807-5c72-41ce-8679-57aa11831fad@linux.dev/
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
---
Link to RFC: https://lore.kernel.org/all/20260117234800.931664-1-matthew.schwartz@linux.dev/
Changes from RFC -> v1: use the proper name for the register field 
---
 drivers/mmc/host/sdhci-pci-gli.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
index b0f91cc9e40e4..7a7be3f7bee6b 100644
--- a/drivers/mmc/host/sdhci-pci-gli.c
+++ b/drivers/mmc/host/sdhci-pci-gli.c
@@ -26,6 +26,9 @@
 #define   GLI_9750_WT_EN_ON	    0x1
 #define   GLI_9750_WT_EN_OFF	    0x0
 
+#define SDHCI_GLI_9750_GM_BURST_SIZE		  0x510
+#define   SDHCI_GLI_9750_GM_BURST_SIZE_R_OSRC_LMT	    GENMASK(17, 16)
+
 #define SDHCI_GLI_9750_CFG2          0x848
 #define   SDHCI_GLI_9750_CFG2_L1DLY    GENMASK(28, 24)
 #define   GLI_9750_CFG2_L1DLY_VALUE    0x1F
@@ -629,6 +632,11 @@ static void gl9750_hw_setting(struct sdhci_host *host)
 
 	gl9750_wt_on(host);
 
+	/* clear R_OSRC_Lmt to avoid DMA write corruption */
+	value = sdhci_readl(host, SDHCI_GLI_9750_GM_BURST_SIZE);
+	value &= ~SDHCI_GLI_9750_GM_BURST_SIZE_R_OSRC_LMT;
+	sdhci_writel(host, value, SDHCI_GLI_9750_GM_BURST_SIZE);
+
 	value = sdhci_readl(host, SDHCI_GLI_9750_CFG2);
 	value &= ~SDHCI_GLI_9750_CFG2_L1DLY;
 	/* set ASPM L1 entry delay to 7.9us */
-- 
2.53.0