mmc: sdhci-pxav2: add register workaround for PXA168 silicon bug

The PXA168 has a documented silicon bug that results in a data abort
exception when accessing the SDHCI_HOST_VERSION register on SDH2 and
SDH4 through a 16-bit read. Implement the workaround described in the
errata, which performs a 32-bit read from a lower address instead. This
is safe to use on all four SDH peripherals.
Signed-off-by: Doug Brown <doug@schmorgal.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20230116194401.20372-4-doug@schmorgal.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-pxav2.c

@@ -80,6 +80,15 @@ static void pxav2_reset(struct sdhci_host *host, u8 mask)
 	}
 }
 
+static u16 pxav1_readw(struct sdhci_host *host, int reg)
+{
+	/* Workaround for data abort exception on SDH2 and SDH4 on PXA168 */
+	if (reg == SDHCI_HOST_VERSION)
+		return readl(host->ioaddr + SDHCI_HOST_VERSION - 2) >> 16;
+
+	return readw(host->ioaddr + reg);
+}
+
 static void pxav2_mmc_set_bus_width(struct sdhci_host *host, int width)
 {
 	u8 ctrl;
@@ -107,6 +116,7 @@ struct sdhci_pxa_variant {
 };
 
 static const struct sdhci_ops pxav1_sdhci_ops = {
+	.read_w        = pxav1_readw,
 	.set_clock     = sdhci_set_clock,
 	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
 	.set_bus_width = pxav2_mmc_set_bus_width,