From: Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
To: Shawn Lin <shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Wenrui Li <wenrui.li-TNX95d0MmH7DzftRWevZcw@public.gmane.org>,
Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>,
Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
Marc Zyngier <marc.zyngier-5wv7dgnIgG8@public.gmane.org>,
linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Brian Norris
<briannorris-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
Subject: [PATCH 6/9] Add comment about why 32-bit read/modify/write isn't safe.
Date: Thu, 01 Sep 2016 11:44:43 -0500 [thread overview]
Message-ID: <20160901164443.14195.13483.stgit@bhelgaas-glaptop2.roam.corp.google.com> (raw)
In-Reply-To: <20160901163758.14195.15725.stgit-1RhO1Y9PlrlHTL0Zs8A6p/gx64E7kk8eUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
---
drivers/pci/host/pcie-rockchip.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
index 17612e5..33bf2e1 100644
--- a/drivers/pci/host/pcie-rockchip.c
+++ b/drivers/pci/host/pcie-rockchip.c
@@ -282,6 +282,11 @@ static int rockchip_pcie_wr_own_conf(struct rockchip_pcie *rockchip,
mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8));
+ /*
+ * N.B. This read/modify/write isn't safe in general because it can
+ * corrupt RW1C bits in adjacent registers. But the hardware
+ * doesn't support smaller writes.
+ */
tmp = readl(rockchip->apb_base + PCIE_RC_CONFIG_BASE + offset) & mask;
tmp |= val << ((where & 0x3) * 8);
writel(tmp, rockchip->apb_base + PCIE_RC_CONFIG_BASE + offset);
--
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next prev parent reply other threads:[~2016-09-01 16:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-01 16:43 [PATCH 0/9] PCI: rockchip: Cleanups against v10 Bjorn Helgaas
2016-09-01 16:44 ` [PATCH 4/9] Rename struct rockchip_pcie_port to struct rockchip_pcie Bjorn Helgaas
2016-09-01 16:44 ` [PATCH 5/9] Use a local "dev" to avoid repetition of "rockchip->dev" Bjorn Helgaas
[not found] ` <20160901163758.14195.15725.stgit-1RhO1Y9PlrlHTL0Zs8A6p/gx64E7kk8eUsxypvmhUTTZJqsBc5GL+g@public.gmane.org>
2016-09-01 16:44 ` [PATCH 1/9] Remove unused symbols, unnecessary parens, other minor comments from Bjorn Helgaas
2016-09-01 16:44 ` [PATCH 2/9] Rename pcie_read() and pcie_write() to rockchip_pcie_read() and Bjorn Helgaas
2016-09-01 16:44 ` [PATCH 3/9] Always use "rockchip" as the pointer to per-device struct Bjorn Helgaas
2016-09-01 16:44 ` Bjorn Helgaas [this message]
2016-09-01 16:44 ` [PATCH 7/9] Simplify the confusing HIWORD_UPDATE scheme Bjorn Helgaas
2016-09-01 16:44 ` [PATCH 8/9] Simplify testing of link status and speed testing Bjorn Helgaas
2016-09-01 20:52 ` [PATCH 0/9] PCI: rockchip: Cleanups against v10 Arnd Bergmann
2016-09-01 16:45 ` [PATCH 9/9] Move msleeps to address Guenter's comments Bjorn Helgaas
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