[PATCH v2] 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/
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
---
Changes in v2:
- Move GM_BURST register defines
- Clear R_OSRC_Lmt in gli_set_9750 instead of gl9750_hw_setting to survive resets
- Link to v1: https://lore.kernel.org/linux-mmc/20260227075909.3860183-1-matthew.schwartz@linux.dev/

Changes in v1:
- Use the proper name for the register field
- Link to RFC: https://lore.kernel.org/linux-mmc/20260117234800.931664-1-matthew.schwartz@linux.dev/
---
 drivers/mmc/host/sdhci-pci-gli.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
index b0f91cc9e40e4..6e4084407662a 100644
--- a/drivers/mmc/host/sdhci-pci-gli.c
+++ b/drivers/mmc/host/sdhci-pci-gli.c
@@ -68,6 +68,9 @@
 #define   GLI_9750_MISC_TX1_DLY_VALUE    0x5
 #define   SDHCI_GLI_9750_MISC_SSC_OFF    BIT(26)
 
+#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_TUNING_CONTROL	          0x540
 #define   SDHCI_GLI_9750_TUNING_CONTROL_EN          BIT(4)
 #define   GLI_9750_TUNING_CONTROL_EN_ON             0x1
@@ -345,10 +348,16 @@ static void gli_set_9750(struct sdhci_host *host)
 	u32 misc_value;
 	u32 parameter_value;
 	u32 control_value;
+	u32 burst_value;
 	u16 ctrl2;
 
 	gl9750_wt_on(host);
 
+	/* clear R_OSRC_Lmt to avoid DMA write corruption */
+	burst_value = sdhci_readl(host, SDHCI_GLI_9750_GM_BURST_SIZE);
+	burst_value &= ~SDHCI_GLI_9750_GM_BURST_SIZE_R_OSRC_LMT;
+	sdhci_writel(host, burst_value, SDHCI_GLI_9750_GM_BURST_SIZE);
+
 	driving_value = sdhci_readl(host, SDHCI_GLI_9750_DRIVING);
 	pll_value = sdhci_readl(host, SDHCI_GLI_9750_PLL);
 	sw_ctrl_value = sdhci_readl(host, SDHCI_GLI_9750_SW_CTRL);
-- 
2.53.0