RE: [PATCH v3] tty: serial: samsung_tty: loopback mode support
From: Chanho Park <hidden>
Date: 2022-07-12 00:46:18
Also in:
linux-samsung-soc, linux-serial
quoted
+ if (mctrl & TIOCM_LOOP) + ucon |= S3C2410_UCON_LOOPBACK; + else + ucon &= ~S3C2410_UCON_LOOPBACK; + + wr_regl(port, S3C2410_UCON, ucon);S3C2410_UCON must be modified at least under the local_irq_save() or port lock, otherwise it breaks kernel console operation on older Exynos SoCs (especially when DMA mode is used). The above read-modify-write sequence should be replaced with the following pattern: if (mctrl & TIOCM_LOOP) s3c24xx_set_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_UCON); else s3c24xx_clear_bit(port, S3C2410_UCON_LOOPBACK, S3C2410_UCON);
All the set_mctrl() call can be protected by spin_[un]lock_irq[save/restore] with port->lock. So, I think it is not required. Best Regards, Chanho Park _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel