linux-kernel - [PATCH 1/1] tpm_tis: handle -EPROBE_DEFER in tpm_tis_plat

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Date:   Fri,  5 Feb 2021 21:20:22 +0100
From:   Dirk Gouders <dirk@...ders.net>
To:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     Dirk Gouders <dirk@...ders.net>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] tpm_tis: handle -EPROBE_DEFER in tpm_tis_plat_probe()

tpm_tis does not consider -EPROBE_DEFER in tpm_tis_plat_probe().
Instead, without notification it falls back to polling mode if
platform_get_irq_optional() returns a negative value.

This could lead to different behavior depending on wether tpm_tis was
compiled builtin or as a module; in the latter case
platform_get_irq_optional() often if not always returns a valid IRQ
number on the first attempt.

Harmonize builtin and module behavior by returning -EPROBE_DEFER,
effectively putting the device on the deferred probe list for later
probe attempts.

Signed-off-by: Dirk Gouders <dirk@...ders.net>
---
 drivers/char/tpm/tpm_tis.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index 4ed6e660273a..4cf863704aa1 100644
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -320,6 +320,9 @@ static int tpm_tis_plat_probe(struct platform_device *pdev)

 	tpm_info.irq = platform_get_irq_optional(pdev, 0);
 	if (tpm_info.irq <= 0) {
+                if (tpm_info.irq == -EPROBE_DEFER)
+                        /* Enter deferred probe list and try again, later. */
+                        return -EPROBE_DEFER;
 		if (pdev != force_pdev)
 			tpm_info.irq = -1;
 		else
-- 
2.26.2