linux-kernel - Re: [PATCH] mmc: block: Add single read for 4k sector cards

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Date:   Fri, 24 Jun 2022 13:58:44 +0000
From:   Christian Löhle <CLoehle@...erstone.com>
To:     "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Avri Altman <Avri.Altman@....com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>
Subject: Re: [PATCH] mmc: block: Add single read for 4k sector cards

Anyone wanting to test this and does not have a way to disturb eMMC signals,
use mmc-utils to disable 512B emulation and something along the lines of:

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 4b70cbfc6d5d..bc0b9241a00f 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -32,6 +32,8 @@
 #include <linux/mmc/sd.h>
 #include <linux/mmc/slot-gpio.h>
 
+#include <linux/sched/clock.h>
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/mmc.h>
 
@@ -141,6 +143,12 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
 	struct mmc_command *cmd = mrq->cmd;
 	int err = cmd->error;
 
+	if (mrq->data && !mrq->data->error && mrq->data->flags & MMC_DATA_READ)
+		if ((sched_clock() % 1000) == 0) {
+			mrq->data->bytes_xfered = 0;
+			mrq->data->error = -EILSEQ;
+		}
+
 	/* Flag re-tuning needed on CRC errors */
 	if (cmd->opcode != MMC_SEND_TUNING_BLOCK &&
 	    cmd->opcode != MMC_SEND_TUNING_BLOCK_HS200 &&
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