| Message ID | 20200422111629.4899-1-adrian.hunter@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mmc: sdhci-pci: Fix eMMC driver strength for BYT-based controllers | expand |
On Wed, 22 Apr 2020 at 13:17, Adrian Hunter <adrian.hunter@intel.com> wrote: > > BIOS writers have begun the practice of setting 40 ohm eMMC driver strength > even though the eMMC may not support it, on the assumption that the kernel > will validate the value against the eMMC (Extended CSD DRIVER_STRENGTH > [offset 197]) and revert to the default 50 ohm value if 40 ohm is invalid. > > This is done to avoid changing the value for different boards. > > Putting aside the merits of this approach, it is clear the eMMC's mask > of supported driver strengths is more reliable than the value provided > by BIOS. Add validation accordingly. > > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> > Fixes: 51ced59cc02e ("mmc: sdhci-pci: Use ACPI DSM to get driver strength for some Intel devices") > Cc: stable@vger.kernel.org Applied for fixes, thanks! Kind regards Uffe > --- > drivers/mmc/host/sdhci-pci-core.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c > index a98c9476bfc8..af736afb4b91 100644 > --- a/drivers/mmc/host/sdhci-pci-core.c > +++ b/drivers/mmc/host/sdhci-pci-core.c > @@ -597,6 +597,9 @@ static int intel_select_drive_strength(struct mmc_card *card, > struct sdhci_pci_slot *slot = sdhci_priv(host); > struct intel_host *intel_host = sdhci_pci_priv(slot); > > + if (!(mmc_driver_type_mask(intel_host->drv_strength) & card_drv)) > + return 0; > + > return intel_host->drv_strength; > } > > -- > 2.17.1 >
diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c index a98c9476bfc8..af736afb4b91 100644 --- a/drivers/mmc/host/sdhci-pci-core.c +++ b/drivers/mmc/host/sdhci-pci-core.c @@ -597,6 +597,9 @@ static int intel_select_drive_strength(struct mmc_card *card, struct sdhci_pci_slot *slot = sdhci_priv(host); struct intel_host *intel_host = sdhci_pci_priv(slot); + if (!(mmc_driver_type_mask(intel_host->drv_strength) & card_drv)) + return 0; + return intel_host->drv_strength; }
BIOS writers have begun the practice of setting 40 ohm eMMC driver strength even though the eMMC may not support it, on the assumption that the kernel will validate the value against the eMMC (Extended CSD DRIVER_STRENGTH [offset 197]) and revert to the default 50 ohm value if 40 ohm is invalid. This is done to avoid changing the value for different boards. Putting aside the merits of this approach, it is clear the eMMC's mask of supported driver strengths is more reliable than the value provided by BIOS. Add validation accordingly. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Fixes: 51ced59cc02e ("mmc: sdhci-pci: Use ACPI DSM to get driver strength for some Intel devices") Cc: stable@vger.kernel.org --- drivers/mmc/host/sdhci-pci-core.c | 3 +++ 1 file changed, 3 insertions(+)