Re: [PATCH v2 23/25] tty: serial: samsung_tty: Add earlycon support for Apple UARTs

On Mon, Feb 15, 2021 at 8:19 PM Krzysztof Kozlowski [off-list ref] wrote:

On Mon, Feb 15, 2021 at 09:17:11PM +0900, Hector Martin wrote:

quoted

+
+/* Apple S5L */
+static int __init apple_s5l_early_console_setup(struct earlycon_device *device,
+                                             const char *opt)
+{
+     /* Close enough to S3C2410 for earlycon... */
+     device->port.private_data = &s3c2410_early_console_data;
+
+#ifdef CONFIG_ARM64

if IS_ENABLED()
(unless it cannot be used due to missing symbol?)

quoted

+     /* ... but we need to override the existing fixmap entry as nGnRnE */
+     __set_fixmap(FIX_EARLYCON_MEM_BASE, device->port.mapbase,
+                  __pgprot(PROT_DEVICE_nGnRnE));
+#endif

It has to be a preprocessor conditional because PROT_DEVICE_nGnRnE
is only defined on arm64. We could add a FIXMAP_PAGE_NONPOSTED
alias for it that defaults to FIXMAP_PAGE_IO, but in the end this is
really an architecture specific thing and I think leaving it guarded by
the architecture is appropriate.

quoted

+     return samsung_early_console_setup(device, opt);

Don't you need to handle the error code - set PROT_DEFAULT() or whatever
was there before?

__set_fixmap() has no return value, it just writes a page table entry and
does not fail.

      Arnd

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